This PDF file contains the front matter associated with SPIE Proceedings Volume 9366 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

We propose a procedure to extract multiple parameters from the spectral characteristic of a single photonic integrated circuit. We applied the method on high order silicon Mach-Zehnder lattice filters:¹ these filters are realized by cascading delay stages and directional couplers of different length. Because of their cascaded nature and steep roll-off properties, these devices can be used to accurately extract properties of the waveguides and the directional couplers. The spectral transmission is measured between the inputs and the outputs. This result is compared to a full CAPHE optical circuit simulation with parametric behavioral models for the waveguide and the directional couplers. An evolutionary fitting algorithm based on the covariance matrix adaptation method is used to match the circuit simulation with the measurement. This black box approach gives us fast and accurate parameter extraction with a reduced number of iteration steps. The quadratic error between measurement and simulation of each iteration is used as feedback for the evolutionary algorithm that adapts the test values for the following step. The objective of our analysis is an accurate, wavelength-dependent model for the waveguide group index and the directional couplers. The proposed method has been used for wafer scale parameter extraction. Our fast method makes it possible to extract the parameters in real time, and correlate the functional parameters of the waveguides with process statistics collected during fabrication. The obtained parameters are in substantial agreement with the results of the simulations used in the design, and can be used to further improve behavioral models that correlate the manufacturing process data with the optical performance.

In the field of modern information technology, optoelectronics are being widely used, and play an increasingly important role. Meanwhile, the demand for more flexible circuit carriers is rapidly growing, since flexibility facilitates the realization of diverse functions and applications. As a potential candidate, transparent polymer substrates with a thickness of about a hundred micrometers by virtue of their low cost and sufficient flexibility are getting more attention. Thus, accomplishing an integration of optoelectronic components into polymer based flexible circuit systems increasingly is becoming an attractive research topic, which is of great significance for future information transmission and processing. We are committed to developing a new microchip bonding process to realize it. Taking into account the fact that most economical transparent polymer substrates can only be processed with restricted thermal loading, we designed a so-called optode instead of a widely adopted thermode. We employ UV-curing adhesives as bonding materials; accordingly, the optode is equipped with a UV irradiation source. An investigation of commercial optoelectronic components is conducted, in which their dimensions and structures are studied. While selecting appropriate transparent polymer substrates, we take their characteristics such as UV transmission degree, glass transition temperature, etc. as key criterions, and choose polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA) as carrier materials. Besides bonding achieved through the use of adhesives cured by the optode, underfill is accordingly employed to enhance the reliability of the integration. We deposit electrical interconnects onto the polymeric substrate to be able to bring the optoelectronic components into electrical operation. In order to enlarge the optical coupling zone from component to substrate within the proximity of the adhesive or underfill, we employ transparent interconnects made of indium-tin-oxide. We present the results of the performance tests, including the contact resistances, mechanical tests and environmental tests.

The devices that are variations of inter-and intracoupled meandering optical waveguides are proposed as the lightwave circuit elements that exhibit distributed feedback. A preliminary transfer matrix method analysis is applied in frequency domain, taking the coupling purely directional and with constant coefficient on geometrically symmetric and anti-symmetric devices. The meandering loop mirror is the building block of all meandering waveguide based lightwave circuit elements. The simplest uncoupled meandering distributed feedback structure exhibits Rabi splitting in the transmittance spectrum. The symmetric and antisymmetric coupled meandering distributed feedback geometries can be utilized as band-pass, Fano, or Lorentzian filters or Rabi splitters. Meandering waveguide distributed feedback structures with a variety of spectral responses can be designed for a variety of lightwave circuit element functions and can be implemented with generality due to the analytic approach taken.

This paper discusses heterogeneous 2D and 3D photonic integration technologies involving various novel fabrication techniques leading to realization of chip-scale microsystems information processing capabilities in the temporal, spectral, and spatial domains. Future prospects and challenges in computing and networking applications will also be discussed.

Widely tunable semiconductor lasers based on a novel half-wave coupler are presented. They have been implemented in the form of half-wave coupled V-cavity and ring-FP cavities. By using the novel half-wave coupler, single-mode lasing with high side-mode-suppression-ratio is achieved. Single-electrode controlled wide-band wavelength tuning with Vernier effect is demonstrated. The full-band tuning of 50 channels with 100GHz spacing is realized by further employing temperature induced gain spectrum shift. The laser is packaged into a small-form-factor 9-pin box TOSA, and the electronic driver has been developed for the wavelength tuning and direct modulation. The advantages of compactness, fabrication simplicity, easy wavelength control and direct modulation allow the tunable lasers to be used in low-cost access and datacenter networks, as well as in portable devices for spectroscopic analysis.

We have harnessed the power of various programmable photonics devices for an interferometric measurement technique. Distortion-free laser-based velocity measurements through a dynamic gas-liquid interface are enabled by a closed-loop optoelectronic system. We are employing electrically tunable lenses and micro mirrors to correct low-order wavefront distortions effectively. Our work represents a paradigm shift in interferometric velocity measurement techniques from using static to dynamic optical elements.

A new heterogeneously integrated III-V/Si laser structure is reported in this letter, which consists of a III-V ridge waveguide gain section on silicon, III-V/Si optical vertical interconnect accesses (VIAs) and silicon-oninsulator (SOI) nanophotonic waveguide sections. The III-V semiconductor layers are introduced on top of the 300 nm thick SOI layer through low temperature, plasma assisted direct wafer-bonding and etched to form III-V ridge waveguide on silicon as the gain section. The optical VIA is formed by tapering the III-V and the beneath SOI in the same direction with a length of 50 μm for efficient coupling of light down to the 600 nm wide silicon nanophotonic waveguide or vice versa. Fabrication details and specification characterizations of this heterogeneous III-V/Si Fabry–Pérot (FP) laser are given. The fabricated FP laser shows a continuous-wave lasing with a threshold current of 65 mA at room temperature and the slope efficiency from single facet is 144 mW/A. The maximal single facet emitting power is about 4.5 mW at a current of 100 mA and the side-mode suppression ratio is ~30 dB. This new heterogeneously integrated III-V/Si laser structure demonstrated enables more complex laser configuration with a sub-system on-chip for various applications.

Aurion's heterogeneous integration platform combines best-in-class passive and active devices in a cost-effective manufacturing process for both military and commercial systems. The resulting silicon photonics chips can be intimately integrated with advanced electronics to enable new system-in-package capability.

We discuss our view of the on-chip optical interconnect infrastructure for future multi-core processers based on wavelength-division-multiplexing (WDM) and our recent results on some key devices for such structures. Cascading performance of various wavelength multiplexers and de-multiplexers including arrayed waveguide gratings (AWGs) and echelle gratings based on the silicon-on-insulator platform are discussed and compared. IIIV based electro-absorption (EA) modulators on silicon realized through benzocyclobutene (BCB) adhesive bonding are analyzed. Ultra short adiabatic taper based mode converters between passive and active structures are designed. The integration of multichannel modulators, detectors and wavelength de-multiplexers is realized.

A fan-in/out polymer optical waveguide is fabricated for connecting multimode multicore (7 cores) fiber with onedimensionally aligned parallel optical components such as a VCSEL/PD array or a multimode fiber ribbon, which is fabricated using the Mosquito method. The Mosquito method we have proposed is a fabrication technique for circular and graded index (GI) cores. One of the unique characteristics of the Mosquito method is a capability of forming threedimensional wirings. In the fan-in/out waveguides, high-density hexagonal alignment of 7 cores at one end is converted to one dimensional alignment with a wider pitch at the other end. For realizing the fan-in/out waveguides, we have issues about low insertion loss, low crosstalk, and the connectability with multicore fibers and optical components. In this paper, we focus in the pitch accuracy of the fan-in/out waveguide. In the Mosquito method, the viscosities of the core and cladding monomers are an important factor of the core figure and the core alignment because the viscosities have a relation to monomer liquid-flow, which could devastate the core alignment. Hence, we investigate the influence of the viscosities of the core and cladding monomers on the interchannel pitch accuracy of the fabricated fan-in/out polymer optical waveguide. With increasing the viscosities of core and cladding monomers, the pitch accuracy is improved, while the appropriate monomer viscosity conditions that can fix all the issues: core circularity and pitch accuracy in both ends still needs to be investigated.

This paper presents an overview of graded refractive index optics based on dual-layer ultrathin film technology and its application in integrated photonics as an on-chip lens for optical coupling of nano-waveguide. The theoretical derivation and discussion shows the equivalence between the dual-layer ultrathin film and a negative birefringent thin film and the influence of thin film thickness and light incident angle on this equivalence. For experimental verification, a set of dual-layer ultrathin films of titanium dioxide (TiO2) and aluminium oxide (Al2O3) are deposited on silicon with different volume fractions. Characterization of refractive index and reflectance shows a good agreement between the experiment and theoretical design, and suggests the graded refractive index profile can be achieved via varying the volume faction of the dual-layer ultrathin film stack. As an application example, a graded refractive index lens with aberration-correction based on the above dual-layer thin film stack is designed and optimized for optical coupling between silicon waveguide and optical fiber. The optical design indicates the multilayer thin-film stack with a proper graded refractive index profile can serve as the passivation cladding on top of silicon waveguide but collimate the light at the waveguide ends for optical coupling to fiber with an estimated efficiency ~89%.

We fabricate low-loss graded index (GI) circular core multimode polymer optical waveguides with 90o bending and demonstrate low bending loss even if the bend radius is as small as 1 mm. In the several fabrication methods for GI-core polymer waveguides already proposed, we adopt the “Mosquito method” that utilize a microdispenser because the Mosquito method makes it possible to fabricate waveguides directly on board at desired places on a printed circuit board, and to draw various patterns of cores including curves. However, in the waveguides including such curved cores, the additional transmission loss due to the bending (bending loss) is a concern. Thus, we characterize the fabricated GI-core polymer waveguides with bending: using two kinds of cladding monomer with different refractive indexes for fabricating waveguides with bending. We found when the NA of waveguides was as high as 0.35, no additional loss due to bending was observed even if the bending radius is as small as 1 mm. The core diameter of the fabricated waveguides is 50 μm, and it is possible to further decrease the bending loss in the waveguides with smaller core diameter. Furthermore, utilizing the Mosquito method, we fabricate waveguides with not only horizontally curved cores but also vertically curved ones. Waveguides with vertically curved cores could make it possible to realize three-dimensionally optical wiring applicable to on-board optical interconnects.

Advanced Driver Assistance Systems (ADAS) are the most advanced technologies to fight road accidents. Within ADAS, an important role is played by radar- and lidar-based sensors, which are mostly employed for collision avoidance and adaptive cruise control. Nonetheless, they have a narrow field-of-view and a limited ability to detect and differentiate objects. Standard camera-based technologies (e.g. stereovision) could balance these weaknesses, but they are currently not able to fulfill all automotive requirements (distance range, accuracy, acquisition speed, and frame-rate). To this purpose, we developed an automotive-oriented CMOS single-photon camera for optical 3D ranging based on indirect time-of-flight (iTOF) measurements. Imagers based on Single-photon avalanche diode (SPAD) arrays offer higher sensitivity with respect to CCD/CMOS rangefinders, have inherent better time resolution, higher accuracy and better linearity. Moreover, iTOF requires neither high bandwidth electronics nor short-pulsed lasers, hence allowing the development of cost-effective systems. The CMOS SPAD sensor is based on 64 × 32 pixels, each able to process both 2D intensity-data and 3D depth-ranging information, with background suppression. Pixel-level memories allow fully parallel imaging and prevents motion artefacts (skew, wobble, motion blur) and partial exposure effects, which otherwise would hinder the detection of fast moving objects. The camera is housed in an aluminum case supporting a 12 mm F/1.4 C-mount imaging lens, with a 40°×20° field-of-view. The whole system is very rugged and compact and a perfect solution for vehicle’s cockpit, with dimensions of 80 mm × 45 mm × 70 mm, and less that 1 W consumption. To provide the required optical power (1.5 W, eye safe) and to allow fast (up to 25 MHz) modulation of the active illumination, we developed a modular laser source, based on five laser driver cards, with three 808 nm lasers each. We present the full characterization of the 3D automotive system, operated both at night and during daytime, in both indoor and outdoor, in real traffic, scenario. The achieved long-range (up to 45m), high dynamic-range (118 dB), highspeed (over 200 fps) 3D depth measurement, and high precision (better than 90 cm at 45 m), highlight the excellent performance of this CMOS SPAD camera for automotive applications.

Advances in CMOS imaging enable image capture at lower light levels. Color detection is also possible where human vision becomes less sensitive in night conditions. In daytime conditions, there are a number of climatic conditions such as rain, fog, snow or smoke etc. that render traditional ‘intelligent’ outdoor cameras that perform various forms of detection and identification tasks relatively ineffective. It has been proven that an adapted five transistor pixel CMOS sensor can perform range-gated active imaging that extends considerably the usability of intelligent cameras in the most difficult conditions. This paper discusses advanced state of the art image sensors with embedded features, with emphasis on the everimportant size, weight, power and cost benefits and discusses the new applications that are enabled.

Luminescent epitaxial β-FeSi2 films were grown on the Ag-layer pre-coated Si(111) substrates. These epitaxial β-FeSi₂ films had (101)/(110)-preferred orientation and were constructed with a triple-domain structure. The full width at half maximum of the rocking curve of β-FeSi₂ 202/220 was 0.19o for the films deposited at 760oC on the Si(111) substrates with 85 nm-thick silver layer. The transmission electron microscope analysis indicated the flat and steep β-FeSi₂/Si interface. The photoluminescence intensity of this (101)/(110)-orientated epitaxial β-FeSi2 films was larger than that of the directly grown β-FeSi₂ films on the Si(111) without silver layer, indicating the decreasing of the density of nonradiative recombination centers in β-FeSi₂ film.