This PDF file contains the front matter associated with SPIE Proceedings Volume 11283, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Silicon photonics is a rapidly maturing platform for optical communication and sensing. As systems leveraging silicon photonics have grown in size and complexity, so too has the demand for high performance silicon photonics components. In order to meet these demands, inverse electromagnetic design has gained attention as a general tool for optimizing sophisticate silicon photonic devices. In this talk, we demonstrate how inverse electromagnetic design methods can be systematically applied to design high performance devices which both satisfy practical fabrication constraints and which are insensitive to manufacturing variations. These results pave the way for high efficiency silicon photonic component libraries.

We use stochastic adjoint optimization to design a new class of integrated photonics devices. They can accomplish highly sophisticated task of information processing such as image recognition. It combines stochastic gradient decent and adjoint state method to solve the optimization problem in nonlinear Maxwell's equations. We also develop approaches to control the minimal feature sizes of the designed devices for easy fabrication.

We proposed and demonstrated a deep learning assisted on-chip Fourier transform spectroscopy (FTS), using an artificial neural networks (ANN) to analyze the output stationary interferogram. It is found that, compared with the conventional FTS, the resolution could be improved without increasing the maximum path length difference and the number of MZIs, thus reducing the burden of adding more power budget. This new concept of enhancing spectral resolution may hold great promise for potential applications in integrated FTS.

The need for light manipulation on the nanoscale has prompted the recent advent and prosperity of plasmonic metastructures. To fully unlock the potential of such engineered optical media, plasmonic structures are exploited with progressively greater complexity, including those with arbitrarily complicated topology, spatially variant building blocks, and multi-layered configurations. The astronomical degrees of freedom associated with such structures have obstructed effective design and implementation schemes based on the conventional wisdom. We have developed a series of deep-learning enabled generative frameworks for the inverse design of plasmonic structures in response to on-demand optical properties, with extended case studies and experimental demonstrations.

We present the first demonstration of a waveguide-integrated dielectric laser accelerator. This structure and associated grating coupler are designed using a gradient-based inverse design approach. A waveguide is directly interfaced with an accelerator structure which is patterned with sub-wavelength features to produce near-fields phase-matched to electrons travelling through a 250 nm gap in the structure. We have experimentally demonstrated these waveguide-integrated accelerators by showing acceleration of subrelativistic electrons of initial energy 83.5 keV. We observe a maximum energy modulation of 1.19 keV over 30 μm. These results represent a significant step toward scalable and integrable on-chip dielectric laser accelerators for applications in ultrafast, medical, and high-energy technologies.

Slow light photonic crystal waveguides (PCW) are a promising tool for optical signal processing and integrated optical devices that require strong light-matter interactions. However, PCWs typically have a large group velocity dispersion (GVD) and low coupling efficiency. In this work, we use inverse design methods to design slow light PWCs with a large group index-bandwidth product (GBP) along with efficient mode converters to couple PCW modes to ridge waveguides and free space. Inverse design is shown to be an effective method for these problems and an essential design method for future PCW applications.

Following the widespread implementation of silicon photonics technology, the emergence of applications in optogenetics, biosensing, augmented reality, and atomic-molecular-optical physics has highlighted a need for integrated photonic platforms operating at visible and ultraviolet wavelengths. Conventional materials for integrated photonics are not well-suited to the task; silicon's 1.1 eV bandgap thwarts its usefulness for wavelengths shorter than the near infrared, and as wavelengths decrease toward the ultraviolet, silicon nitride likewise begins to falter and strong material absorption takes hold. Meanwhile, aluminum oxide grown by atomic layer deposition (ALD) is a largely unexplored material which exhibits low material loss deep into the ultraviolet. ALD alumina keeps several desirable characteristics of silicon nitride; namely easy deposition on a variety of substrates and processing with commonly-available tooling. Here I discuss recent work developing ALD aluminum oxide for building integrated photonic systems, with an emphasis on fabrication and recent measured results. I review results for waveguides and resonators in the visible-to-ultraviolet regime, using both vertical grating couplers and inverse-taper edge couplers for input/output. Measured ring resonators at λ = 405 nm exhibit intrinsic quality factors exceeding 470,000, and propagation loss is measured from 0.5 dB/cm at λ = 461 nm to < 3 dB/cm at λ = 370 nm.

TiO₂ is gaining interest as material for integrated photonics, due to its high refractive index, large transparency window and high non-linear refractive index. Its low phonon energy makes it attractive for the realization of active devices in the visible frequency range. In this work, we optimize different process steps of the fabrication of low loss TiO₂ channel waveguides. The TiO₂ layers are deposited by DC sputter deposition, using a mixed Ar/O₂ plasma. Removing the hysteresis in the deposition process, results in reduced propagation losses of the TiO₂ films (estimated less than 1.5 dB/cm at 632 nm wavelength). An E-beam lithography process is utilized to reduce the sidewall roughness of the waveguides. Different reactive gasses are compared to optimize the reactive ion etching recipe. BCl₃ in combination with HBr shows to be most beneficial for etching TiO₂ with high selectivity towards negative E-beam resist. A selectivity of 2.7 for TiO₂ over the E-beam resist is obtained. The performance of a TiO₂ a channel waveguide fabricated with the process before and after optimization is compared. The waveguide fabricated using the non-optimized process exhibited losses of 7.82±0.52 dB/cm at a wavelength of 632.8 nm, after applying an SiO₂ cladding. After process optimization, 5.08±0.65 dB/cm were obtained, without an SiO₂ cladding.

The grand challenge of integrated optics comes from the materials and their compatibility. In order to achieve several distinct functions on a same chip, several materials must be combined together. This yields fabrication issues that are difficult to avoid while working at the micro- or nano-scale. Efficient proofs-of-concepts have demonstrated the well operation of very complex devices, for an everyday use, these components are costly and difficult to manufacture. We propose to discuss the advantages of strip-loaded photonics, for which the question of the guiding materials is almost not a problem. Several experimental examples will be presented.

We present the design strategy of shallow-angle grating couplers for vertical emission from InP devices, and then discuss the focusing effect of a 2D grating. Measured beam shapes from prototyped devices agree well with the simulation results.

Nonreciprocal optical functionalities like optical isolators and circulators are key components for the suppression of unwanted optical feedback in lasers and are also widely used for light routing in fiber-based measurement systems such as optical coherence tomography. Therefore, they are important building blocks in integrated optics, which promises further miniaturization and cost reduction of optical elements for telecom, datacom, and sensing applications. In this work, we experimentally demonstrate a four-port polarization independent optical circulator on a polymer-based hybrid integration platform. The circulator consists of polymer waveguides and two thin-film polarization beam splitters (PBSs) inserted into waveguides via etched slots. Crystalline, pre-magnetized bulk Faraday rotators (FRs) and half-wave plates (HWPs) are inserted into free-space sections, formed by pairs of waveguide butt-coupled GRIN lenses. For a first demonstrator, on-chip losses down to 5 dB and optical isolations up to 24 dB were measured, depending on the different input and output constellations, as well as the polarization. By applying an external magnetic field opposite to the magnetization of the faraday rotators, it is possible to repole the magneto-optic material, leading to reversely circulating light inside the device. This enables optical switching between ports in form of a latching switch, which maintains its state after removing the external magnetic field.

We investigate a fourth-order PT symmetric optical sensor and analyze its eigenfrequency phase diagram. The four eigenfrequencies of our optical sensor simultaneously collapse at the high-order exceptional point in parameter space, providing a quarter root relation between the frequency splitting amount and the perturbation. A clear sensitivity boost is observed when comparing the frequency splitting with other optical sensors under small perturbation condition.

An integrated refractive index gas sensor working in the Mid infrared (MIR) region and utilizing suspended silicon waveguide is presented. Although many integrated refractive index gas sensors have been proposed in the literatures, their operating wavelength is limited to the near infrared range. Our proposed gas sensors can operate in the mid infrared up to 10μm, were many gases have their absorption fingerprints in order to enhance the sensing performance. A finite difference solver is used to perform the sensitivity analysis of the suspended silicon waveguide in the MIR range for gaseous medium. The analysis shows that a suspended silicon waveguide can achieve high waveguide sensitivity with a minimal mode loss. Thus, we designed a high performance Mach Zehnder Interferometer (MZI) gas sensor using a suspended silicon waveguide as the sensing arm. Three dimensional finite difference time domain (3D-FDTD) solver is used in the design and optimization of two designs. One for the wavelength interrogation scheme of detection and another one for the intensity interrogation scheme. The first design, exhibits high wavelength sensitivity S=7028 nm/RIU and can reach high figure of merit (FOM) of around 180 RIU^-1 for both wavelength and intensity interrogation methods with only 250μm sensing arm length. The second design furtherly enhances the intensity interrogation FOM to reach 370RIU^-1 at the same length. Intensity interrogation needs only a laser source and a detector. Hence, using our sensor in intensity interrogation based read-out offers compact, low cost and mass scale fabrication which makes our proposed sensor a good platform for lab on chip technology.

We demonstrate electromechanical Brillouin scattering in telecom-band integrated photonics platforms based on AlN 1D and 2D optomechanical waveguides. In the former, 16 GHz acoustic modes, which are excited with nanofabricated electromechanical transducers, scatter counterpropagating optical modes into a single anti-Stokes sideband. In the latter, 11 GHz acoustic modes deflect optical modes by 60° in a planar device with integrated transducers, waveguides, and lenses, realizing unprecedented large-angle acousto-optic beam deflection. Our work shows the promises of such new integrated acousto-optic device platforms as efficient interfaces between microwave and optical photons, which may lead to potential applications in on-chip beam steering and routing, optical spectrum analysis, high-frequency acousto-optic modulators, RF or microwave photonics filters and delay lines, as well as nonreciprocal optical dev

In this paper, we report our recent advances in the development of CMOS compatible PECVD silicon nitride waveguide based photonic key building blocks for optical coherence tomography (OCT) in the 850 nm wavelength region and for biosensing applications in the visible domain around 650 nm wavelength. We discuss the design and experimental verification of compact low-loss waveguide bends, broadband couplers with varying power splitting ratios required for PIC based OCT systems, arrayed waveguide gratings for spectral domain OCT, and a monolithically integrated optically pumped organic solid-state laser for low-cost biosensing applications.

Evanescent field based integrated optics have great potential as a chip-based platform for label-free detection of molecular interactions. Implementation of the waveguides in an optical interferometric scheme allows for a very sensitive label-free sensor array platform as in this case small changes of the refractive index caused by the molecule capturing are easily detected. The unsurpassed sensitivity of especially the aMZI (asymmetric-Mach-Zehnder interferometer) sensor, in combination with the extreme uniformity of these sensing arrays allows for screening of proteins as well as small molecule drug candidates. However, to become interesting for the market, much more has to be in place: optimized surface functionalization chemistry, combination with microfluidics, and preferably hybrid integration of lightsource(s) and detector(s). In this proceedings the specific aMZI sensor chip design, surface modification, readout mechanisms and first results with multiplexing two specific cancer biomarker protein (POSTN and TGFBI) will be discussed. Initial experiments show a limit of detection of 1 ng/ml (~10 pM) of POSTN in buffer solution.

We report a highly sensitive ultrasound sensor based on an integrated photonics silicon Mach-Zehnder interferometer (MZI). One arm of the MZI is located on a thin membrane, acting as the sensing part of the device. Ultrasound waves excite the membrane’s vibrational mode, thus inducing modulation of the MZI transmission. The measured sensor transfer function is centered at 0.47 MHz and has a −6 dB bandwidth of 21.2%. For 1.0 mW optical input power, we obtain a high sensitivity of 0.62 mV/Pa, a low detection limit of 0.38 mPa/Hz^1/2 at the resonance frequency and a large dynamic range of 59 dB. In preliminary ultrasound imaging experiments using this sensor, an image of a wire phantom is obtained. The properties of this sensor and the generated image show that this sensor is very promising for ultrasound imaging applications.

In this paper, we propose a new type of subwavelength grating (SWG) racetrack resonator with engineered coupling condition and waveguide nanostructure. Highly dispersive coupling condition between bus waveguide and SWG ring is achieved, which has a V-shape envelope of resonance spectrum, through adjusting the SWG unit shape, dimension and the length of directional coupling region. When top cladding refractive index changes, instead of indicated in single resonant wavelength shift, which is the case for conventional SWG ring resonator, the movement of the spectrum envelope peak actually represents the sensitivity of our device. SWG racetrack resonators with two different widths are investigated, showing much bigger spectrum shift compared with the conventional one. The results may provide a new approach for further improve device sensitivity and hold great promise for potential applications in integrated optical sensor.

Next-generation fiber-optic communication systems require dramatically increased complexity that cannot be obtained using discrete optical components. Silicon photonics has a unique capacity of handling complexity. We review our recent progress in high-speed silicon photonic transmitters and space-division multiplexers to scale the capacity of fiber-optic networks towards terabits-per-second (Tb/s) per optical interface and petabits-per-second (Pb/s) per transmission link.

Silicon photonics and coherent communications are a near perfect match. Coherent requires complex transceivers with polarization diversity, multi-element modulators, hybrids, ease of packaging with electronics, etc.; and silicon photonics favors applications that use external lasers because of its indirect bandgap. The commercial success of this marriage has helped generate silicon photonics offspring in other areas, including short-reach non-coherent communications, optical coherent tomography, LiDAR, and deep learning.

Correcting phase errors is key to building low cost, high performance integrated optical phased arrays for mass-market applications such as automotive lidar. In this work, we present a phase interrogator component for optical phased arrays which enables the phase error to be measured immediately before the output array of optical emitters. A 32-element silicon/silicon nitride optical phased array is realized in a dual layer photonics stack to verify the component performance. Silicon enables high density integration of photonic components and the phase interrogator has a compact design which fits between waveguides with a separation of 2.5 μm. The phase interrogators enable correction of the beam without any measurement or evaluation of the far-field.

Owing to its low-cost, high-yield, and dense integration ability, silicon nanophotonics is a good candidate to tackle the needs of exponentially growing communications in data centers, high-performance computers, and cloud services. Moreover, a number of nanophotonic functions are now available on a single chip, as they take advantages of silicon-foundry process maturity and epitaxial germanium integration. Optical photodetectors are key building blocks in the library of group-IV components and their performances are quite successful nowadays. In particular, silicon-germanium waveguide-integrated photodetectors are fixing new standards for next generation of on-chip interconnects in terms of compactness, speed, power consumption and cost. Indeed, conventional pin photodetectors yield good responsivities (~1 A/W in a 1.5 μm wavelength range), high bandwidths (~50 GHz), and dark currents well below 1 μA. Despite recent advances, their optical power sensitivities remain rather modest and speeds are limited to 25 Gbps only, however. Compensating for the insufficient photodetector sensitivity requires higher transmitter output powers and therefore higher energy consumption. Additional energy savings can be obtained by eliminating receiver electronics. Alternatively, an appealing approach is to exploit device structures with an internal multiplication gain to lower even more the power budget and improve energy efficiency of chip-based optical links. In this work, we report on waveguide-integrated photodetectors with lateral silicon-germanium-silicon heterojunctions. Here, we present avalanche photodetectors fabricated on 200-mm silicon-on-insulator wafers using complementary metal-oxide-semiconductor-compatible processes. Devices operate in the low-gain-regime to facilitate high-speed link operations at 1.55 μm wavelengths. An error-free signal detection was achieved at 28 Gbps, with power sensitivity of -11 dBm for 10^-9 bit-error-rate, which is a relevant link rate for emerging chip-scale optical interconnects.

The field of Programmable Photonics is of increasing interest. Many programmable circuits utilise thermal switches to carry out the programming function, which introduces a significant continuous power requirement, which is unsustainable in the longer term. Silicon Photonics has proved a popular substrate to support these circuits as Silicon has a significant thermos-optic co-efficient, and is growing in maturity as a photonic platform. In this work we have developed a way to both programme photonic devices as well as tuning their operating point, in a semi-permanent manner, to remove the need for continuous power to sustain a given circuit configuration.

We report on the use of programmable silicon photonic meshes of thermally tuneable interferometers to manipulate dynamically guided-wave and free-space optical beams on a chip through arbitrary linear transformations. Several applications are presented, including automatic reconstruction and unscrambling of mixed optical modes; forming and steering of free-space optical beams; coupling of free-space beams from arbitrary directions of arrival to single-mode waveguides; phase front reconstruction and beaming through scattering media. Automatic self-configuration of the meshes is achieved by exploiting built-in transparent monitors, beam labelling and thermal crosstalk cancellation strategies, enabling scalability to photonic meshes with a large number of interferometers.

Femtosecond laser micromachining (FLM) is a powerful technique that allows for rapid and cost-effective fabrication of photonic integrated circuits (PICs), even when a complex 3D waveguide geometry is required. Among the features of these devices, it is worth mentioning the possibility to dynamically reconfigure the circuit by thermal phase shifting. However, an integrated microheater dissipates more than 500 mW to induce a 2π phase shift in FLM devices operating at telecom wavelength (i.e. 1550 nm) and induces significant thermal crosstalk to adjacent devices. These issues prevent the integration of more than a few microheaters on the same chip. In order to cope with this, we exploited a new water-immersion FLM process to integrate high-quality single-mode waveguides (0.29 dB/cm propagation losses and 0.27 dB/facet coupling losses at 1550 nm) with two different types of thermally insulating microstructures: trenches on the sides of the heated photon path and a bridge waveguide, a structure in which the ablation is performed also under the optical path. Both the strategies are employed for the fabrication of compact reconfigurable Mach-Zehnder interferometers having inter-waveguide pitch down to 80 μm. Interferometers featuring insulating trenches show a reconfiguration period down to 57 mW, whilst bridge waveguides result in a further improvement, with a 2π phase shift that can be induced with an electrical power as low as 37 mW. Both structures reduce thermal crosstalk from more than 50% down to 3:5% on the nearest device.

Tuneable all-optical signal processing has been the holy grail of information photonics; it has been pursued for many years but has proven to be very challenging. In this contribution, we present our recent work in developing an all-optical signal processing device called a photonic reservoir computer (PhRC) which can be tuned to perform a bespoke task. The PhRC is inspired by how the brain handles and process information. We demonstrate that a chaotic micro-resonator is a suitable platform for the optical implementation of such an artificial neural network.

Neuromorphic photonics is an emerging field at the nexus of photonics and neuroscience, which combines the advantages of optics and electronics. By combining the high bandwidth and efficiency of photonic devices with the reconfigurability and parallelism of optical architectures, photonic processors have the potential to be faster than state-of-the-art electronic processors while consuming less energy per computation. We will look at the traditional challenges of photonic information processing, describe some photonic neural-network approaches, discuss their applications in neuromorphic computing and machine learning, and talk about the scalability of these platforms.

We present a theoretical and experimental study of topological modes running along string-like disclinations in two-dimensional electromagnetic lattices. Two-dimensional honeycomb lattices can host lattice defects of five- and seven-membered rings, which serve as the fixed termination points for string-like disclination. The strings act upon the Dirac cone states in a manner analogous to Dirac strings. When a band gap is opened by breaking sublattice symmetry, gap-spanning interface states appear along the strings, similar to topological kink states in valley Hall systems. But unlike the valley Hall case, the edges can have arbitrary orientations and terminate at fixed points in the bulk. The theoretical and numerical analysis is rigorously verified through microwave experiments.

The failure of conventional electronic architectures to solve large combinatorial problems motivates the development of novel computational architectures. There has been much effort recently in developing photonic networks which can exploit fundamental properties enshrined in the wave nature of light and of its interaction with matter: high-speed, low-power, optical passivity, and parallelization. However, unleashing the true potential of photonic architectures requires the development of featured algorithms which largely exploit these fundamental properties. We here present the Photonic Recurrent Ising Sampler (PRIS), an algorithm tailored for photonic parallel networks that can sample combinatorially hard distributions of Ising problems, in a fast and efficient manner. The PRIS finds the ground state of general ising problems and is able to probe critical behaviors of universality classes and their critical exponents. In addition to the attractive features of photonic networks, the PRIS relies on intrinsic dynamic noise to find ground states more efficiently.

Chalcogenides are a material platform for infrared nonlinear optics with high transmission and nonlinearity, but are susceptible to changes in bond structure during fabrication. These changes affect both the linear and nonlinear optical properties of the chalcogenide. We analyze the structure and optical properties of thermally evaporated and annealed Ge₂₈Sb₁₂Se₆₀ to determine why these changes occur and how they can be rectified. We observe that thermally evaporated Ge₂₈Sb₁₂Se₆₀ has an increased selenium content, increased bandgap, increased concentration of heteropolar bonds, and lower third order nonlinearity. We further observe that annealing above the glass transition temperature reduced the concentration of heteropolar bonds and increased the third order nonlinearity by a factor of four.

The most general motion of a system is a superposition of its normal modes, or eigenstates. For Hermitian system, classical normal mode theory applies. For non-Hermitian systems, presently a lot of progress is done to describe the response of optical micro and nanoresonators in their quasinormal mode basis. We have developed a rigorous modal analysis of nanoresonators with unprecedented generality and report numerical results for the general case of 3D resonators, made of dispersive materials on substrate with guiding layers.

The fabrication of a novel optical biosensor based on Bloch long-range surface plasmons on waveguide arrays is presented in this work. The structures are fabricated on a truncated 1D photonic crystal comprised of a 12 period stack of alternating layers of SiO₂/Ta₂O₅. The Au waveguides, are fabricated using a bi-layer lift-off photolithography process including LOR 1A and SPR 955. Grating couplers, as the input/output means, are fabricated using overlaid electronbeam lithography involving a bilayer PMMA process. The planar waveguides are integrated into arrays capable of multichannel multimodal biosensing. The wafer is covered with CYTOP as the upper cladding with etched microfluidic channels, and wafer-bonded to a borofloat silica wafer to encapsulate the fluidic channels and enable side fluidic interfaces.

This presentation explores the possibility of an using extrusion process in order to manufacture a new type of optical fiber based biomedical sensors. With the extrusion method, any number of fibers can be integrated in the sensor to fulfill different requirements. The extrusion process is known for its reliability and enables the manufacture of any length of sensor without reproducibility issues. The emphasis is placed on shape sensing of needles and catheters for minimally invasive surgery. Shape sensing is performed using the enhanced backscatter signal of our ROGUEs (random optical fiber gratings written by UV or ultrafast laser exposure).

We present an investigation into the resolution of blazed chirped Bragg grating spectrometers. These are dispersive spectrometers that diffract light out of a waveguide at a wavelength dependent angle, whilst focusing the light. The spectral resolution is found to be inversely proportional to grating length; previously used fabrication schemes limited the grating length (and hence resolution) when creating compact devices. We propose and implement a solution to this problem by varying the blaze angle of a Bragg grating along its length. Initial results show the fabrication of longer gratings (while preserving focal length) and an increase in FWHM resolution from 0.57 nm to 0.52 nm. This increase in resolution is thought to be limited by the appearance of aberrations which can be corrected for in future devices.

Photonics integration in the mid-Infrared (mid-IR) spectral range, and more specifically the fingerprint region between 5 and 20 μm wavelength has garnered a great interest as it provides an immense potential for applications in spectroscopy and sensing. The unique vibrational and rotational resonances of the molecules at these wavelengths can be exploited for non-intrusive, unambiguous detection of the molecular composition of a broad variety of gases, liquids or solids, with a great interest for many high-impact applications. Fourier-transform spectrometers (FTS) are a particularly interesting solution for the on-chip integration due to their superior robustness against fabrication imperfections. However, the performance of current on-chip FTS implementations is limited by tradeoffs between bandwidth and resolution, for a given footprint. In this work we propose and experimentally demonstrate a new FTS approach that gathers the advantages of spatial heterodyning and optical path tuning by thermo-optic effect. The high resolution is provided by spatial multiplexing among different interferometers with increasing imbalance length, while the broadband operation is enabled by fine sampling interval of the optical path delay in each interferometer harnessing the thermo-optic effect. This novel approach overcomes the bandwidth-resolution tradeoff in conventional counterparts. The fabricated device enables a bandwidth as wide as 603 cm^-1 (instead of 74 cm^-1 with no-thermal tuning) near 7.7 μm wavelength, keeping a resolution better than 15 cm^-1 with the same footprint. This device is fabricated in a Ge-rich graded-index SiGe platform with experimentally proven low loss operation up to 8.5 μm wavelength.

On-chip spectroscopy in visible and near-infrared wavelength offers immense potential for various screening and diagnostic application. Silicon Nitride (SiN) is a promising material to realize on-chip spectroscopy as it is transparent over a broad wavelength spectrum; visible-to-mid-infrared. Besides, it is compatible with the CMOS process technology. Since SiN can be deposited using various deposition techniques, it is essential that an appropriate deposition process is chosen to achieve desired properties. We present a detailed study of SiN films deposited using PECVD and LPCVD process. The films were characterized for various, material and optical properties. We also performed waveguide transmission measurement on different SiN films and found a strong correlation with material properties such as stress and autofluorescence to achieve low-loss waveguide. Using the optimized material, we design, fabricate, and demonstrate single-mode SiN wire, spiral waveguides and grating fiber-chip coupler at visible (λ =520nm) and near infra-red (λ = 780nm) wavelengths used for spectroscopy.

Furthermore, we use a waveguide to efficiently excite fluorescence or Raman active molecules drop casted as the top cladding of the waveguides. A fraction of the isotopically emitted fluorescence or Raman signal couples back to waveguide and rest is emitted normal to the surface. We discuss the theoretical efficiencies of both the methods of collection and compare it with the conventional microscope-based spectroscopic system. Waveguide based spectroscopic sensing offers higher efficiency due to increased light-matter interaction along the length of the waveguide. We presented detailed design, simulation, and experimental demonstration of grating coupler waveguide system suitable for son-chip spectroscopy application.

We propose and demonstrate the fabrication of wire array metamaterial fibers and hyperlenses based on Ag₇₂Cu28 wires embedded in borosilicate glass for imaging applications at mid-infrared frequencies. Initial numerical modeling indicates smaller optical losses for such a system in comparison to the equivalent Sn/soda-lime structures reported recently in the literature. Modeling of the proposed and fabricated magnifying hyperlenses shows promising overall optical losses between 11 dB to 16 dB (depending on the structural parameters) when operating at 5 μm wavelength. Their experimental characterization and the proof-of-concept far-field sub diffraction imaging experiment are in progress.

An integrated refractive index gas sensor working in the Mid infrared (MIR) region and utilizing suspended silicon waveguide is presented. Although many integrated refractive index gas sensors have been proposed in the literatures, their operating wavelength is limited to the near infrared range. Our proposed gas sensors can operate in the mid infrared up to 10μm, were many gases have their absorption fingerprints in order to enhance the sensing performance. A finite difference solver is used to perform the sensitivity analysis of the suspended silicon waveguide in the MIR range for gaseous medium. The analysis shows that a suspended silicon waveguide can achieve high waveguide sensitivity with a minimal mode loss. Thus, we designed a high performance Mach Zehnder Interferometer (MZI) gas sensor using a suspended silicon waveguide as the sensing arm. Three dimensional finite difference time domain (3D-FDTD) solver is used in the design and optimization of two designs. One for the wavelength interrogation scheme of detection and another one for the intensity interrogation scheme. The first design, exhibits high wavelength sensitivity S=7028 nm/RIU and can reach high figure of merit (FOM) of around 180 RIU-1 for both wavelength and intensity interrogation methods with only 250μm sensing arm length. The second design furtherly enhances the intensity interrogation FOM to reach 370RIU-1 at the same length. Intensity interrogation needs only a laser source and a detector. Hence, using our sensor in intensity interrogation based read-out offers compact, low cost and mass scale fabrication which makes our proposed sensor a good platform for lab on chip technology.

Current research in CO2 catalytical conversion is usually conducted with single-pass lab-scale reactors. Operating conditions affecting catalyst performance optimized for these reactors were not necessarily transferrable for large scale applications. Herein we report a scalable optofluidic photoreactor based on glass waveguides coated with photocatalyst. Inside the “shell-and-tube” reactor design, tubes are replaced by internal light-guiding waveguides with specially designed scattering surfaces to enable deep and efficient penetration of the light irradiation. Using reverse water–gas shift (RWGS) as a pilot reaction, the effect of temperature, light irradiation and residence time on the photocatalytic activity of this photoreactor platform was examined.

When producing milk in the dairy industry, reliable quality assurance systems need to be in place in order to detect allergens which can potentially harm humans upon consumption. Milk can very often be contaminated with hazardous antibiotics used by farmers to treat cows. Current quality assurance biosensors are manual methods and prone to lots of human error. Failure during this process can be financially harmful to dairy companies, and potentially harmful to human health. This shows a necessity for an automated biosensor to detect antibiotics in milk before shipment. This work presents an automated biosensor based on microchip electrophoresis and fluorescence spectroscopy to detect ciprofloxacin in milk, which is a commonly used antibiotic to help treat mastitis of cows. The design and testing results of the low-cost system are presented in this paper. In order to detect the presence of the antibiotic, the milk sample needs to be separated into its constituents. This is achieved by using the phenomenon of electroosmotic flow to allow the mixture to travel down the microchannel, followed by electrophoresis to separate it into its molecules. After this separation occurs, the constituents are illuminated with a UV LED source of 280 nm, as ciprofloxacin will emit fluorescence at 440 nm at this illumination wavelength. This fluorescence is detected using a photodiode, and the output voltage of the photodiode indicates the ciprofloxacin concentration within the milk. This lab-on-a-chip biosensor proved to be reliable and is a good solution to automate antibiotic detection in milk.

Very high switching speed can be achieved for Photonic CMOS transistors, using low-resistance, low forward voltage, high quantum efficiency lasers or light emitting diodes, and high photon absorption rate avalanche photo diodes. The MOSFET, laser, and photon sensor are integrated as one transistor. In this paper we will illustrate how to improve the performance of a photonic MOSFET with layout design, fabrication, and device technologies.

This paper analyzes an approach for additively manufacturing polymer optical waveguides. The production process includes flexographic printing of conditioning lines (5 μm height) on a substrate, which are used as guiding barriers in the subsequent printing of the optical core. The core is additively printed (up to 50 μm in height) with an aerosol jet printer, filling the gap between the conditioning lines. The conditioning lines do not only enhance the contact angle of the polymer, which results in a higher cross section of the waveguides, but also improve the straight edges of the printed waveguides. We show that the quality of the conditioning lines is directly correlated to the waviness of the waveguides. Consequently, the analyses of the waviness of the conditioning lines classifies the quality of the fabricated waveguides. However, the waviness of the waveguides can also be considered in optical simulations. In this paper we show how we derive a waveguide model with waviness by fitting a single sine function onto the topological data of the conditioning lines. With this model a variation of the waviness can easily be simulated and goals for fabrication can be set. With the simulations it is possible to verify that the measured waviness (period of 559.5 μm and an amplitude of 4.99 μm) does not affect the optical quality of the waveguides.

Thermoplastic polyetherimides (ULTEM™ and EXTEM™ resins) have been used to produce complex optical lenses and ferrules that are integrated in optical interconnect sub-assemblies. Current thermoplastic optics must be added separately to prevent dimensional changes from the 260°C peak temperature of a solder reflow process. This paper covers injection molding parameters and solder reflow conditions that influence optical properties and dimensional stability of solder-reflowable test components.

Robust and economic but precise and high-resolution analysis of optical spectra is of immense interest in optical communications, spectroscopy, sensing, and many other fields. Conventional optical spectrum analyzers utilize either movable gratings, interferometers, heterodyning or Brillouin scattering. Besides the large size, limited robustness and high costs, spectrometers with a high resolution, like interferometers and Brillouin scattering, usually measure only limited bandwidths, while grating-based spectrometers can measure a large bandwidth but, with limited resolution. Here we present preliminary results of a silicon integrated optical spectrum analyzer with wide operational range and high resolution. The device utilizes two spectral filtering devices in succession, namely an integrated high-Q microring resonator with tunable resonance frequency and a wavelength division demultiplexer. The narrow resonances of a tunable ring resonator enable high resolution measurements of the power distribution of unknown signals at multiple positions according to the free spectral range. Subsequently, the individual resonances are separated by a wavelength division demultiplexer with a much broader bandwidth. The narrow and equidistant resonances are placed so that each resonance falls within a separate channel of the demultiplexer. The power of each subchannel is monitored during tuning of the ring by simple low bandwidth photodiodes. If one scan corresponds to the tuning of the ring resonances over the full width of one channel of the demultiplexer, the combination of all channels will represent the whole spectrum of the signal under test. Preliminary experiments show a resolution of 98 MHz.

We describe the use of resonant amplification of light propelling forces for selective separation of fluid-suspended dielectric microparticles. The force amplification and the selectivity of the method is achieved using the whispering gallery mode resonances of the microparticles. The selectivity is determined by the inverse of the quality factor (Q) of the resonances in liquid (with Q ~ 10⁴-10⁶). We demonstrate that the evanescent field around a tapered optical fiber fed with ~20 mW power from a 1064 nm laser can selectively move polystyrene microspheres of up to 20 μm in diameter through distances of more than 50 μm, thereby establishing that the technique is sufficient for efficient separation.

The authors employ a novel PIC to demonstrate athermalised transmission under direct modulation. The unique architecture of the chip enables compensation of thermal redshift of laser wavelength through control of self-heating. The PIC consists of 2 lasers in a master-slave configuration. Such a structure improves the performance of a free running laser (slave) by optical injection from another laser (master). The benefits reaped from such a PIC structure implementing optical injection include chirp minimisation, linewidth reduction, and improved modulation response. Experimental demonstration of 2.5 Gb/s OOK data transmitted over 37 km with error-free performance over the temperature range 10-45°C is presented.

Advancements in continuous and digital microfluidics (DMF) for integrated optics technologies are improving the feasibility of biophotonic sensors within lab-on-a-chip devices. Lab-on-a-chip diagnostic devices are achieving unprecedented high levels of throughput. Digital microfluidics, with its reconfigurable nature, is often utilized over continuous microfluidic systems due to reagent economy, precision, potential for scalability, and independent fluid actuation. However, scalability within DMF systems is currently inhibited by the DMF sensing architectures that are presently used, being capacitance and resistance sensing. These electrical-based sensing architectures probe each microdroplet location and this is difficult to scale. In this work, a fibre-optic sensing architecture is developed to improve scalability and achieve independent sensing of microdroplets. The sensing architecture utilizes an m × n (column and row) perpendicular overlap grid structure of embedded fibre-optic cables that yields m × n sensing positions with m + n measurement points. To evaluate both localized and practical scalability of the system, actuation contact time and differentiation of multiple microdroplets are assessed. The embedded fibre-optic cables will distribute light proportional to the number of microdroplets in contact along the column or row. Differentiation of multiple microdroplets is assessed with a theoretical model and through experimental measurements. The DMF sensing architecture is demonstrated for a three by three grid with multiple microdroplets present. The results show compatibility with high-speed DMF operation (due to fast contact times) and demonstrate scalable sensing of multiple microdroplets.

A high extinction ratio polarization beam splitter (PBS) based on cascaded multimode interference couplers is designed on silicon on insulator substrate using 3D beam propagation method (BPM). The numerical simulation tool shows that the polarization extinction ratio is greater than 20 dB for both TE and TM polarizations over C-band wavelength range. The proposed device has insertion loss below 0.8 dB at wavelength 1550 nm for TE and TM polarization. The polarization beam splitter has a compact size and relaxed fabrication tolerance in term of width and length of MMI coupler. These parameters make it as a promising element for polarization diversity circuit and photonic integrated circuits.

In this work we study various types of photonic waveguides for gas sensing in mid-infrared (MIR) region. MIR region which contains the absorption peaks of many gases is the most suitable region for gas detection. Operating near the absorption peak of the gas to be detected enhance the sensor performance significantly as both real and imaginary parts of the detected gas refractive index are maximized, which enhance the sensitivity and leads to lower detection limit. Here we focus on refractive index sensors that relies on the detection of the real part (n) of the refractive index. Refractive index sensors are strong candidates for integrated on chip sensors, where a small sample volume is needed. One of the main parameters in designing refractive index sensor is waveguide sensitivity which is defined as the ratio of the waveguide effective index change to the medium refractive index change, S_wg=Δn_eff/Δn_med. Thus rigorous sensitivity analysis using full-vectorial finite difference mode solver have been carried out to determine the waveguide sensitivity of such waveguides to gaseous medium. We use silicon on sapphire (SOS) platform to operate in the MIR region from 2μm to 6μm. For each structure we make sensitivity analysis once with undoped silicon and once with doped silicon to show how converting the same structure from dielectric to plasmonic will affect its performance as sensor. The dependence of the effective index, sensitivity and mode loss of each waveguide on the different waveguide dimensions was studied. Finally, a comparison between the proposed waveguides is provided.

Non-contact printing methods have recently attracted attention in the field of optoelectronics manufacturing including solar cells, light-emitting diodes, photodetectors, and transparent electrodes. Non-contact printing is a powerful and cost-effective technique for high-precision processing through the direct printing of optoelectronic devices. Multimode optical waveguides which are generally fabricated by lithography or reactive ion etching reported exhibiting minimum losses of 0.02 dB/cm and 0.2 dB/cm, respectively. Although these techniques are well established in the fabrication process, it is complicated and possible only with large-scale equipment. Non-contact printing technique can be used to solve these problems. In this paper, we design and demonstrate the printing of optical waveguides with a flexible substrate. The waveguide width was advanced through the nozzle design within 500 μm and applied to the high voltage and nozzle structure so that the capillary force does not damage the pattern.

The integration of the transparent ITO/NiO/ITO Resistive Random-Access Memory (ReRAM) with vertically-coupled bus waveguides, which is ultimately emerged as a ReRAM-based microdisk resonator fabricated on lithium niobate (LiNbO3) substrate, is successfully realized. The transparent ITO and NiO layers are deposited by radio-frequency sputtering technique, while the bus waveguides in LiNbO3 is achieved by a proton-exchange method. The ReRAM-based microdisk resonator thus designed and fabricated have dual functionality of memory and optical spectral filtering capabilities. When the ReRAM microdisk resonator is electronically set at different memory states, that is, ReRAM is alternatively set in high-resistance state (HRS) and low-resistance state (LRS), the corresponding spectral shifts detected at both through and drop ports are noticeable different, when compared with those obtained before and after subjecting the ReRAM to a required forming process. Specifically, the spectral shift associated with the LRS state of ReRAM between the through and drop port terminal is around 4.4 nm, as compared to the spectral shift of approximately 1.7 nm that is associated with the HRS state of ReRAM between the same two terminals. The aforementioned characteristics of selective light wave filtering can be selectively tuned by varying the ReRAM device dimensions. The adoption of the different thin-film materials for the ReRAM fabrication may also play an important role in spectral tuning. Most important of all, because of different spectral shifts observed, the particular memory state of ReRAM could possibly and uniquely be interrogated by an optical means. The resultant discovery opens a new pathway in the future to the realization of one of the new optical memory devices.

In recent years many research groups have delved into the research and development of Resistive Random-Access Memory (ReRAM) which has the combined advantages of fast read/write speed, simplicity in structure, small device size and density, low activation bias voltage, low power consumption, allowably many periodic operating cycles and nonvolatile memory feature. In order to operate RRAM in an ultraviolet (UV) spectroscopic regime, the spectral transparency of electrodes and reliable device performance are keys to ensuring its continual applicability. Among the materials considered, nickel oxide (NiO) potentially has a broad perspective in optical applications due to their relatively wide bandgap, high mobility, high transparency, remarkably good electrical and optical characteristics. It is foreseeable in the future that the unique applicability of RRAM in UV will make its headway as a key component in many optoelectronic displaying products. The present study focuses on using Radio Frequency Magnetron Sputtering method to prepare NiO active layer and indium tin oxide (ITO) top electrode for the realization of RRAM devices and their current-voltage (I-V) and capacitance-voltage (C-V) characteristics are subsequently evaluated with and without the irradiation of ultraviolet light. Specifically, a series of reliability tests show that the fabricated memories have endured up to 100 switching cycles and the current contrast ratio between high (HRS) and low (LRS) resistance state at 0.1V has achieved more than two orders of magnitude. Furthermore, the retention time measurement has also demonstrated that the memory storage capability of these RRAMs remains in excellent operating condition after surviving more than 10,000 seconds of the test. Major attention is concentrated on finding out a correlation between the UV responsivity and switching characteristics for NiO RRAMs biased at low voltage. We found that the memory states associated with the RRAM of the smallest feature sizes could be toggled relatively easily by UV irradiation at the smallest size.

A new aerosol jet printed lead-zirconium-titanate (PZT) actuated scanner for potential 2D scanning application is proposed. The proposed actuator combines a microfabricated PZT MEMS actuator with an off-the-shelf taper optical fiber for a simple overall design. The actuator is fabricated by constructing a 5 μm layer of high quality PZT thin film directly on a 60 μm thick stainless-steel substrate using aerosol deposition method. A chemically etched single-mode optical fiber (SM600) is epoxied onto the cantilever arm of the actuator structure to serve as the scanning waveguide. The scanner is driven at its resonant frequency of 896 Hz and 5650 Hz and the vertical tip displacement of up to 343 μm is achieved with a ±36V input. The finite element analysis of the actuator pad and the fabrication procedure for the design are presented. A comparison of the frequency response test results of the proposed scanner from the harmonic analysis in simulation, laser vibrometer and the optical observing methods is also discussed.

Both long haul and short distance network interconnects for conventional data networks and intra-/interchip data links continue to scale in complexity and bandwidth. This has signalled the emergence of the optical interconnect, with silicon photonics being the leading candidate due to its unique combination of low fabrication costs and performance enhancements. Electronic-photonic integration compatibility with CMOS technology, makes integrated photonic circuits more appealing. Hence, it is very critical to make the fabrication of integrated photonic devices as foundry compatible as possible to fully utilize CMOS foundry capabilities. We have proposed a fabrication method for thin film lithium niobate (LN)-based electro-optic modulators which has excellent compatibility with silicon photonic foundry processes and minimizes the back end of the line processes. This paves the way for large scale production of the hybrid Silicon-lithium niobate devices.

Theoretical performance analysis of optical filters is usually done assuming an incident plane wave. This may be a good indicator of the device performance when the spot size of the incident beam is much greater than the operating wavelength. However, in practice the incident beam is usually focused on a very small spot to fit the device footprint. Such focused beams contain a range of incident angles, i.e., a set of different plane waves. Thus, a degradation is expected in the filter spectral transmission behavior when compared to that theoretically determined by using a plane wave model. Angle tolerant filters are filters that preserve their spectral properties under a wide range of angles. This work aims at studying the effect of an inclined Gaussian beam finite spot size on the transmission performance of a five-layer angle-tolerant hybrid plasmonic multilayer filter structure by applying beam expansion method analysis. For spot sizes of 10 micrometers, the filter transmission preserves its shape for different angles of incidence. As the spot size narrows to 0.1 micrometers, transmission preserves its shape but loses around 8% compared to plane wave case. Further deterioration is observed for the same spot size at an angle of incidence of 50 degrees. The behavior is found to be limited by the filter’s field of view (FOV). The FOV of the filter we used in the study is around 50 degrees. Hence, with narrower beams, a larger angular divergence is present which cannot be compensated by the angle tolerance of the filter. To the best of our knowledge, similar work has not been studied in existing literature.

Ring lasers, evanescently coupled to an adjacent optical waveguide, are essential components for the upcoming generation of integrated sources. In an ideally symmetric resonator, emission occurs from the both clockwise and counter-clockwise directions, resulting in a potential waste of emitted optical power, while unidirectional emission has been reported in different configurations, for example when asymmetric external reflectivities are used for the coupling waveguide. In the integrated form, a common approach consists in the inserting an S-bend waveguide in the ring, in such a way that the field propagating in the direction that we want to suppress is reinjected in the other direction. The S-bend waveguide must be carefully designed to reduce optical losses and to ensure a sufficient suppression of the undesired field. Using 2D finite- difference time-domain simulations performed with Synopsys RSoft©, we report a systematic analysis of the racetrack geometry of a 86.8 μm long microring laser including an inner S-waveguide, and we maximize the unidirectionality of the ring laser, scanning the gap distance between external racetrack resonator and S-bend waveguide. The results of this numerical analysis can be finally used to generate the mask layout of the improved unidirectional ring laser, targeting a Process Design Kit of choice, taking advance of the integration of RSoft with the software OptoDesigner.©