This PDF file contains the front matter associated with SPIE Proceedings Volume 9359, including the Title Page, Copyright information, Table of Contents, Authors, and Conference Committee listing.

Two-dimensional (2D) semiconductors possess unique optoelectronic properties and has become a research hot-spot in recent years. Realized that the sizable and thickness-dependent bandgap offers transition metal dichalcogenides (TMDCs) a huge potential in the development of photonic devices with high performance and unique functions, we studied extensively the ultrafast NLO property of a range of TMDCs. TMDCs with high-quality layered nanosheets were prepared using liquid-phase-exfoliation technique. Ultrafast saturable absorption, two-photon-absorption were observed from the 2D nanostructures. The exciting results open up the door to 2D photonic nano-devices, such as optical switches, mode-lockers, optical limiters, etc., capable of ultrafast response and broadband tunability.

Widely wavelength tunable soliton self-frequency shift (SSFS) from 1.58 μm to 2.07 μm was experimentally demonstrated in a highly nonlinear fiber pumped with a mode-locked sub-100 fs Er-doped fiber laser. The maximum output spectrum (full width at half maximum, FWHM) around 2 μm is 143 nm. Although the pulse width of SSFS was measured to be a few picoseconds, the large FWHM bandwidth of SSFS spectrum shows that soliton with sub-50 fs could be achieved if the giant chirped pulse is efficiently re-compressed to be transforms limited. Dispersive wave with a minimum pulse width of 50 fs was also observed.

We have investigated stimulated Raman scattering in the 4H polytype of SiC, due to its excellent thermal conductivity which is of great importance for power scaling of Raman lasers. Spectroscopy verifies the sample’s polytype and precludes any significant admixture of other polytypes. Tests indicate the moderate optical quality of this commercially available sample. Using pump-probe measurements around 1030 nm, we find the Raman gain coefficient of the major peak at 777 cm^-1 to be 0.46 cm/GW. Although this value is only modest, calculations and experience with other Raman materials indicate that Raman lasing of 4H SiC should be possible with reasonable intensities of 1064-nm pulsed pumping.

In frame of the European Marie Currie project GRIFFON [http://astonishgriffon.net/] the usage of a green approach in terms of reduced power consumption and maintenance costs is envisioned for long-span fiber networks. This shall be accomplished by coherent transmission in unrepeatered links (100 km – 350 km) utilizing ultra-long Raman fiber laser (URFL)-based distributed amplification, multi-level modulation formats, and adapted Digital Signal Processing (DSP) algorithms. The URFL uses a cascaded 2-order pumping scheme where two (co- and counter-) ∼ 1365 nm pumps illuminate the fiber. The URFL oscillates at ∼ 1450 nm whereas amplification is provided by stimulated Raman scattering (SRS) of the ∼ 1365 nm pumps and the optical feedback is realized by two Fiber Bragg gratings (FBGs) at the fiber ends reflecting at 1450 nm. The light field at 1450 nm provides amplification for signal waves in the 1550 nm range due to SRS. In this work we present URFL design studies intended to characterize and optimize the power and noise characteristics of the fiber links. We use a bidirectional fiber model describing propagation of the signal, pump and noise powers along the fiber length. From the numerical solution we evaluate the on/off Raman gain and its bandwidth, the signal excursion over the fiber length, OSNR spectra, and the accumulated nonlinearities. To achieve best performance for these characteristics the laser design is optimized with respect to the forward/backward pump powers and wavelengths, input/output signal powers, reflectivity profile of the FBGs and other parameters.

Homogeneous, 200 – 3000 nm thick layers of chalcogenide glasses, 1 – 2 mm thick plane-parallel plates as well as nanocomposite structures, containing gold nanoparticles have been produced and used for in situ surface optical and geometrical relief fabrication by optical- or electron-, ion-beam recording. Investigations were focused on the formation of giant (height modulation from nanometers up to micrometers) geometrical reliefs and elements (dots, lines and diffractive elements) applicable in the 0.5 – 10 micrometer spectral range. Recording parameters were compared with available data on acrylic polymer nanocomposites. The mechanism of the recording processes, which include thermal, electron and mass-transport components were explained and the selection of the materials from As(Ge)-S(Se) binary systems with best recording parameters was done.

Porous MgF₂ films synthesized by a sol-gel method exhibit the lowest refractive index among the dielectric optical materials and are the most useful materials for the anti-reflection coatings. On the other hand, surface plasmon resonance (SPR) absorptions of noble metal nanoparticles in various solid matrices have been extensively studied. New functional materials like a SERS (Surface Enhanced Raman Spectroscopy) tips are expected by synthesizing composite materials between porous MgF₂ films featured by the network of MgF₂ nanoparticles and noble metal nanoparticles introduced within the network. In this study, fundamental physical properties including morphology and optical properties are characterized for these materials to make clear the potential of the composite system. Composite materials of MgF₂ films dispersed with noble metal (Ag, Au) nanoparticles were prepared using the sol-gel technique with various annealing temperatures and densities of noble metal nanoparticles. The structural morphology was analyzed by an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). The size and shape distributions of the metal nanoparticles were observed using a transmission electron microscope (TEM). The optical properties of fabricated composite films were characterized by UV-Vis-NIR and FT-IR spectrophotometers. The absorption spectra due to the surface plasmon resonance (SPR) of the metal nanoparticles were analyzed using the dielectric function considering the effective medium approximation, typically Maxwell-Garnett model. The Raman scattering spectra were also studied to check the enhancement effect of specimen dropped on the MgF₂: Ag nano-composite films deposited on Si substrate. Enhancement of the Raman intensity of pyridine solution specimen was observed.

Digital cameras are present everywhere in our daily life. Science, business or private life cannot be imagined without digital images. The quality of an image is often rated by its color rendering. In order to obtain a correct color recognition, a near infrared cut (IRC-) filter must be used to alter the sensitivity of imaging sensor. Increasing requirements related to color balance and larger angle of incidence (AOI) enforced the use of new materials as the e.g. BG6X series which substitutes interference coated filters on D263 thin glass. Although the optical properties are the major design criteria, devices have to withstand numerous environmental conditions during use and manufacturing - as e.g. temperature change, humidity, and mechanical shock, as wells as mechanical stress. The new materials show different behavior with respect to all these aspects. They are usually more sensitive against these requirements to a larger or smaller extent. Mechanical strength is especially different. Reliable strength data are of major interest for mobile phone camera applications. As bending strength of a glass component depends not only upon the material itself, but mainly on the surface treatment and test conditions, a single number for the strength might be misleading if the conditions of the test and the samples are not described precisely,. Therefore, Schott started investigations upon the bending strength data of various IRC-filter materials. Different test methods were used to obtain statistical relevant data.

Acousto-Optic Tunable Filters with large acceptance angle (parallel tangent configuration) are the component of choice for imaging application in visible and NIR region wavelength. AOTF in the wavelength range above 2μm could be impractical due to the λ² and interaction length dependencies on acoustic field intensity to achieve peak diffraction efficiency. A potential solution to reduce the RF power requirement for full diffraction efficiency is to realize a resonant acoustic cavity, and "recycle" the phonons. This configuration could give a theoretical advantage factor between 4 and 10. A prototype device with an operational wavelength range between 1μm and 2μm has been designed and tested and an optimized design to operate between 2μm - 4μm has been prepared and under construction. Due to the presence of standing wave, when the device is not in resonance a feedback signal from the device is affecting the electrical matching and the power delivered to the device is mostly reflected back (VSWR > 25), therefore a special RF driver is required in order to maintain in resonance the device. The resonance frequencies are also affected by the temperature of the device, thus a temperature control mechanism with high accuracy is required. We present the preliminary results of the first prototype, which are in good agreement with the mathematical model and an advantage factor of about 4 has been measured. Further investigation are planned in order to improve the device performance and develop the RF driver for the resonant configuration.

Chalcogenide glasses are known for their large transparency in the mid-infrared and their high linear refractive index (>2). They present also a high non-linear coefficient (n₂), 100 to 1000 times larger than for silica, depending on the composition. we have developed a casting method to prepare the microstructured chalcogenide preform. This method allows optical losses as low as 0.4 dB/m at 1.55 µm and less than 0.05 dB/m in the mid IR. Various chalcogenide MOFs operating in the IR range has been fabricated in order to associate the high non-linear properties of these glasses and the original MOF properties. For example, small core fibers have been drawn to enhance the non linearities for telecom applications such as signal regeneration and generation of supercontinuum sources. On another hand, in the 3-12 µm window, single mode fibers and exposed core fibers have been realized for Gaussian beams propagation and sensors applications respectively.

We report on the rapid prototyping platform, developed at Fibercore, for producing spun multicore fiber (MCF) which maintains the high-specification and quality of a large-scale manufacturing process adding the versatility to fully customize fiber for specific applications. Such MCF has been produced by using an ultrasonic drill to accurately position the core holes in the cladding glass, achieving <0.4µm accuracy in fiber. Cross-talk between cores has been minimized by implementing high numerical aperture cores of 0.20, with levels less than -55dB over 400m. Additionally, the high level of germanium doping also allows fiber Bragg gratings (FBGs) to be written into each core without the need for hydrogen loading. Finally, in order to enable distinction between any potential twist and strain in the fiber from the bend under measurement, a permanent twist has been introduced in the fiber by spinning the preform whilst it is being drawn. The manufacturing cycle time for the fiber is 8 days, allowing rapid prototyping and repeat development cycles to be tested over a short period of time when creating new fiber designs.

Microstructured optical fibers (MOFs) are a major achievement in the field of optical fiber technology. Owing to their unprecedented design flexibility, MOFs have found numerous applications in various fields of photonics. By adapting the parameters of the holey cladding, MOFs with tailored dispersion properties, large mode area, endlessly single mode operation and high non-linear response can be designed and fabricated. This paper deals with designing MOFs with a specific microstructure that would allow increasing the efficiency with which fiber gratings can be photo-inscribed in a MOF. The air holes are usually impeding the delivery of optical power to the core region, which results in a lower grating writing efficiency. This problem is exacerbated when using IR femtosecond laser sources for the inscription, as the induced refractive index changes stem from a highly non-linear multi-photon absorption process and are hence very dependent on the optical intensity that actually reaches the MOF core. In this paper we first study regular hexagonal lattice MOFs to find a range of lattice parameters that would facilitate femtosecond grating inscription, considering the non-linear nature of the index change. To assess the influence of the microstructured cladding on the transverse delivery of light to the core region, we introduce a figure of merit to which we refer as ‘transverse coupling efficiency’ (TCE). Second, we evaluate the index changes that would be obtained when implementing a special type of holey structure that acts as a transversely focusing microstructure – known as Mikaelian lens – in the cladding of the MOF.

New methods for fiber Bragg grating inscription in optical fibers use femtosecond laser sources, which can induce refractive index changes even in non-photosensitive fibers and which allow achieving gratings that remain stable at high temperatures. The index change takes place as a result of a highly non-linear multi-photon absorption process. Although such gratings were successfully inscribed in conventional fibers, there are still challenges involved when attempting to fabricate femtosecond gratings in microstructured optical fibers (MOFs). The air holes are usually impeding the delivery of optical power to the core region, which results in a lower grating writing efficiency. In this paper we report on our numerical computations that aim to estimate the influence of the MOF’s holey cladding on the induced index change during interferometric grating inscription with an infrared (IR) femtosecond laser source. For high power femtosecond laser pulses at 800 nm the refractive index change in silica stems from a highly non-linear five photon absorption process. Using empirical data on refractive index changes from literature and intensity distribution data from our transverse coupling simulations we propose an approach to reconstruct the non-linear refractive index modification in the MOF core region. We then study the influence of the MOF angular orientation on the induced index change and we model the impact of MOF tapering as a possible way to increase the grating writing efficiency.

We propose a reflection type metal-insulator-metal (MIM) metasurface composed of hybrid optical antennas for comprehensive spatial engineering the properties of optical fields. Its capability is illustrated with an example to create a radially polarized vectorial beam for optical needle field generation. Functioning as local quarter-wave-plates (QWP), the MIM metasurface is designed to convert circularly polarized incident into local linear polarization to create an overall radial polarization with corresponding binary phases and desired normalized amplitude modulation ranged from 0.07 to 1. To obtain enough degrees of freedom, the optical-antenna layer comprises periodic arrangements of double metallic nano-bars with perpendicular placement and single nano-bars respectively for different amplitude modulation requirements. Both of the antennas enable to introduce π/2 retardation while reaching the desired modulation range both for phase and amplitude. Through adjusting the antennas’ geometry and array carefully, we shift the gap-surface plasmon resonances facilitated by optical antennas to realize the manipulation of vectorial properties. Designed at 1064 nm wavelength, the particularly generated vectorial light output can be further tightly focused by a high numerical aperture objective to obtain longitudinally polarized flat-top focal field. The so-called optical needle field is a promising candidate for novel applications that transcend disciplinary boundaries. The proposed metasurface establishes a new class of compact optical components based on nano-scale structures, leading to compound functions for vectorial light generation.

In this paper, a novel meta surface is proposed for super-focusing. This surface contains two slits surrounded by finite corrugations for enhanced focusing. This simple surface has the super-focusing ability to focus both near and far field light in a hot-spot with FWHM much smaller than half the wavelength of the incident light. The structure is suitable for one dimensional and two dimensional focusing applications. The enhanced transmission through the double slit is also utilized for directional beaming over a wide cone of angles. Moreover, various structures have been proposed for superfocusing in the visible and ultraviolet wavelengths. The proposed structure lends itself to various applications including subwavelength imaging and nanolithography.

Fused fiber components are critical building blocks for power scaling and reliable operation of fiber laser systems. We review different fiber fusion methods for fabricating fused fiber components, and show some examples of splicing of dissimilar fibers, fiber combiners, and fiber caps with high power handling capability, which enable power scaling of fiber lasers.

Optical fiber is made of glass, an insulator, and thus it is immune to strong electromagnetic interference. Therefore, fiber optics is a technology ideally suitable for sensing of partial discharge (PD) both in transformers and generators. Extensive efforts have been used to develop a cost effective solution for detecting partial discharge, which generates acoustic emission, with signals ranging from 30 kHz to 200 kHz. The requirement is similar to fiber optics Hydro Phone, but at higher frequencies. There are several keys to success: there must be at least 60 dB signal-to-noise ratio (SNR) performance, which will ensure not only PD detection but later on provide diagnostics and also the ability to locate the origin of the events. Defects that are stationary would gradually degrade the insulation and result in total breakdown. Transformers currently need urgent attention: most of them are oil filled and are at least 30 to 50 years old, close to the end of life. In this context, an issue to be addressed is the safety of the personnel working close to the assets and collateral damage that could be caused by a tank explosion (with fire spilling over the whole facility). This paper will describe the latest achievement in fiber optics PD sensor technology: the use of phase shifted-fiber gratings with a very high speed interrogation method that uses the Pound-Drever-Hall technique. More importantly, this is based on a technology that could be automated, easy to install, and, eventually, available at affordable prices.

We report on the creation of Fiber Bragg Gratings (FBGs) based sensors in large mode area (LMA) fibers. By using a quintupled Nd:YVO₄ laser at 213 nm wavelength, FBGs are produced in conventional double clad fibers with core diameters of up to 50 µm. Bragg wavelength shifts depending on applied tensile strain as well as temperature changes are recorded and operating ranges of strain sensors identified. The ease of coupling with light sources into LMA fibers as well as their comparatively elevated robustness makes them promising sensor solutions for harsh environments.

Yb:CALGO is now recognized to exhibit outstanding properties for the production of high-power and ultra-short laser pulses in the near infrared spectral range. However, various UV-visible absorption bands can be also observed due to different types of charge transfer mechanisms. Some of them are assigned to the formation of color centers due to small polarons and others to O^2-→Yb³⁺ ligand-to-metal charge transfer (LMCT) transitions. The former can be removed by using adequate thermal treatments. The latter are intrinsic and they are very intense with cross sections of about two orders of magnitude larger that the near infrared ones. In fact, such LMCT absorption bands are responsible for relatively large changes of ionic polarizabilities and to non-negligible pseudo-nonlinear changes of refractive indices which should certainly affect the laser properties of Yb:CALGO at high pump power levels.

In this work, we report the near infrared and upconversion emissions of Er³⁺-doped transparent fluorotellurite glassceramics obtained by heat treatment of the precursor Er-doped TeO₂-ZnO-ZnF₂ glass. Structural analysis shows that ErF₃ nanocrystals nucleated in the glass-ceramic sample are homogeneously distributed in the glass matrix with a typical size of 45±10 nm. The comparison of the fluorescence properties of Er³⁺-doped precursor glass and glass-ceramic confirms the successful incorporation of the rare-earth into the nanocrystals. An enhancement of the red upconversion emission due to ⁴F_9/2→⁴I_15/2 transition together with weak emission bands due to transitions from ²H_9/2, ⁴F_3/2,_5/2, and ⁴F_7/2 levels to the ground state are observed under excitation at 801 nm in the glass-ceramic sample. The temporal evolution of the red emission together with the excitation upconversion spectrum suggest that energy transfer processes are responsible for the enhancement of the red emission.

Rare-earth-ion-doped materials are of high interest as amplifiers and lasers in integrated optics. Their longer excited-state lifetimes and the weaker refractive-index change accompanied with rare-earth-ion excitation compared to electron-hole pairs in III-V semiconductors provide spatially and temporally stable optical gain, allowing for high-speed amplification and narrow-linewidth lasers. Amorphous Al₂O₃ deposited onto thermally oxidized silicon wafers offers the advantage of integration with silicon photonics and electronics. Layer deposition by RF reactive co-sputtering and micro-structuring by chlorine-based reactive-ion etching provide low-loss channel waveguides. With erbium doping, we improved the gain to 2 dB/cm at 1533 nm and a gain bandwidth of 80 nm. The gain is limited by migration-accelerated energy-transfer upconversion and a fast quenching process. Since stimulated emission is even faster than this quenching process, lasers are only affected in terms of their threshold, allowing us to demonstrate diode-pumped micro-ring, distributed-feedback (DFB), and distributed-Bragg-reflector (DBR) lasers in Al₂O₃:Er³⁺ and Al₂O₃:Yb³⁺ on a silicon chip. Surface-relief Bragg gratings were patterned by laser-interference lithography. Monolithic DFB and DBR cavities with Q-factors of 1.35×10⁶ were realized. In an Er-doped DFB laser, single-longitudinal-mode operation at 1545 nm was achieved with a linewidth of 1.7 kHz, corresponding to a laser Q-factor of 1.14×10¹¹. Yb-doped DFB and DBR lasers were demonstrated at 1020 nm with output powers of 55 mW and a slope efficiency of 67% versus launched pump power. A dual-phaseshift, dual-wavelength laser was achieved and a stable microwave signal at ~15 GHz was created via the heterodyne photo-detection of the two laser wavelengths.

In this paper we investigate photodarkening and photobleaching impact in 1030 nm ytterbium doped fiber lasers and we compare results with previous experiments made with 1070 nm fiber lasers built from the same kind of alumino-silicate fiber. The possibility of using a common model with no free parameters may suggest that lower photodarkening experienced in 1030 nm fiber lasers is simply due to lower inversion required, with no influence due to the wavelength of laser photons.

Gold nanoparticle embedded in Er³⁺-Tm³⁺-codoped tellurite-glass are able produce two effects on the emission properties these glasses: (i) quenching on direct-emission under excitation by a 405 nm laser diode, or (ii) enhancement on upconversion-emission under excitation by a 976 nm laser diode in these glasses. Both effects were investigated from the luminescence decay dynamics of ions. The localized surface plasmon resonance band of gold nanoparticles at around 580 nm resulted in the quenching/enhancement of Er³⁺-Tm³⁺ emission for the Er³⁺:(⁴S_3/2→⁴I_15/2) transition. These hybrid materials can be utilized for various photonic applications, e.g. infrared to visible light converters or emitting green light.

We report on the fluorine incorporation in powder based materials for the fabrication of Al and Al/Yb co-doped silica glasses. The achieved maximum Fluorine concentration of 1.55 mol% SiF₄ corresponds to a refractive index decrease of -8 x 10^-3. Simultaneously, the Tg of the doped material is reduced by about 200 K compared to pure silica. Moreover, the fluorine doping is also eminently suitable for the direct refractive index adjustment in active doped silica glass materials (e.g. Al/Yb or Al/Tm). The index matching with pure silica is possible to date up to 2.7 mol% Al₂O₃ and 0.1 mol% Yb₂O₃. The additional influence on the blue shift of the UV transmission will also be discussed.

We report a light-dispersing device comprised of two transmission gratings and a wave plate. The gratings split the light incident at the Bragg angle into two orthogonally polarized components. The wave plate, which is placed between the gratings, functions as a polarization converter for oblique illumination. Appropriate assembly of these optical parts results in efficient diffraction of the unpolarized light with high spectral resolution. Using coupled-wave theories and Mueller matrix analysis, we constructed a device with a grating period of 400 nm for the spectral range of 680 ± 50 nm. We verified the proposed polarization-independent light-dispersing concept from the evaluation of this device.

Random anti-reflection structured surfaces (rARSS) have been reported to improve transmittance of optical-grade fused silica planar substrates to values greater than 99%. These textures are achieved using reactive-ion etching techniques and often result in transmitted spectra with no measurable interference effects (fringes) for a wide range of wavelengths. The inductively-coupled reactive ion plasma (ICP-RIE) used in the fabrication process to etch the rARSS is anisotropic, and thus well-suited for planar components. The improvement in spectral transmission has been found to be independent of optical incidence angles, for values from 0° to ±30°. Qualifying and quantifying the rARSS performance on curved substrates, such as concave and convex lenses, is required to optimize the fabrication of a desirable AR effect on opticalpower elements. In this work, rARSS was fabricated on fused silica plano-convex and plano-concave lenses, using an optimized ICP-RIE process, to maximize optical transmission in the range from 500 nm to 1100 nm. Results are presented from optical transmission tests of matched sets of varying curvature lenses with rARSS at a wavelength of 633nm. The transmission was measured as a function of radial distance from the apex of each lens, and shows the anisotropic dependence of the etch process. The transmittance profiles between the different sphericity of the tested lenses as well as the matched sets of concave and convex surfaces are compared. The measured angle-of-incidence dependence of planar silica versus silica lenses with rARSS is also presented.

Packaging can have a significant impact on the performance characteristics of Silicon Photomultipliers (SiPM) sensors as well as having an impact on reliability and yield. To provide the highest performance possible, SensL have recently developed and tested a surface mount, through silicon via (TSV) package that provides high array fill factor, high photon detection efficiency (PDE) and magnetic resonance imaging (MRI) system compatibility. The PDE of TSV packaged sensors will be shown to be the highest when compared to traditional SiPM package types. In addition the PDE in the UV and blue region will be shown to approach that of unprotected bare die. Additionally, the TSV package has minimal deadspace outside of the active area which will be shown to allow close packing when used in a sensor array. It will be shown that arrays of TSV sensors have the highest fill factor currently possible when creating arrays from singulated die. Additionally, it will be shown that TSV parts are non-magnetic and results of images taken with the TSV SiPM in a 3 Tesla magnetic resonance imaging (MRI) system will be shown to have no impact on the MRI system.

Silicon Photomultipliers (SiPMs) are emerging single photon detectors used in many applications requiring large active area, photon-number resolving capability and immunity to magnetic fields. We present three families of analog SiPM fabricated in a reliable and cost-effective fully standard planar CMOS technology with a total photosensitive area of 1×1 mm². These three families have different active areas with fill-factors (21%, 58.3%, 73.7%) comparable to those of commercial SiPM, which are developed in vertical (current flow) custom technologies. The peak photon detection efficiency in the near-UV tops at 38% (fill-factor included) comparable to commercial custom-process ones and dark count rate density is just a little higher than the best-in-class commercial analog SiPMs. Thanks to the CMOS processing, these new SiPMs can be integrated together with active components and electronics both within the microcell and on-chip, in order to act at the microcell level or to perform global pre-processing. We also report CMOS digital SiPMs in the same standard CMOS technology, based on microcells with digitalized processing, all integrated on-chip. This CMOS digital SiPMs has four 32×1 cells (128 microcells), each consisting of SPAD, active quenching circuit with adjustable dead time, digital control (to switch off noisy SPADs and readout position of detected photons), and fast trigger output signal. The achieved 20% fill-factor is still very good.

SensL C-Series Silicon Photomultiplier (SiPM) sensors are fabricated in a high-volume CMOS foundry to a custom SensL process, and packaged as a reflow solderable surface mount device. Advances in SiPM production have resulted in significant improvement in PDE, dark current as well as tighter breakdown voltage uniformity for the C-Series SiPM sensors. The SiPM are fabricated with a shallow P-on-N junction optimized for the detection of shorter wavelength photons, with a peak PDE of 41% at 420nm and excellent sensitivity extending to wavelengths <300nm. The dark currents have been reduced through the reduction of damage during semiconductor processing and an order of magnitude reduction has been achieved. The breakdown voltage variation has been improved through process optimization to minimize variations. With these process improvements typical dark count rates of ~30kHz/mm² are achieved simultaneously with breakdown voltage uniformity of ±213mV demonstrated. In addition, application specific measurements of CRT (Coincidence Resolving Time) that are relevant to PET (positron emission tomography) will be shown to be 210ps at 7.5V overvoltage. In addition to device characterization work, this paper will address the wafer-level fabrication and testing, package level testing required by high volume SiPM sensor applications.

In this paper, we have analyzed the effect of multi-input injection on the hysteresis width and rising-falling time of output signal at the dominant mode and the suppressed-injected mode of the single mode Fabry-perot laser diode (SMFP-LD). The dominant mode of SMFP-LD can be changed with the change in operating temperature and has a tunability of about 10 nm. The analysis of hysteresis width is useful for choosing the appropriate input power and wavelength detuning for input injected beam according to its applications. Latching application needs larger hysteresis width whereas for switching application lesser hysteresis width is preferred for less switching time. The hysteresis analysis is used to demonstrate short pulse controlled all-optical switch which includes SR latch as a control unit and 1x2 switch as a switching unit. Input control pulses are used to switch input data of 10 Gbps to output ports and the minimum control pulse observed is 280 ps. Clear waveforms, eye diagram and rising/falling time at outputs are obtained for the proposed optical short pulse controlled switching circuit.

Short-range interconnection and/or data center networks require high capacity and a large number of channels in order to support numerous connections. Solutions employed to meet these requirements involve the use of alternative wavebands to increase the usable optical frequency range. We recently proposed the use of the T- and O-bands (Thousand band: 1000–1260 nm, Original band: 1260–1360 nm) as alternative wavebands because large optical frequency resources (>60 THz) can be easily employed. In addition, a simple and compact Gb/s-order high-speed optical modulator is a critical photonic device for short-range communications. Therefore, to develop an optical modulator that acts as a highfunctional photonic device, we focused on the use of self-assembled quantum dots (QDs) as a three-dimensional (3D) confined structure because QD structures are highly suitable for realizing broadband optical gain media in the T+O bands. In this study, we use the high-quality broadband QD optical gain to develop a monolithically integrated QD optical gain modulator (QD-OGM) device that has a semiconductor optical amplifier (QD-SOA) for Gb/s-order highspeed optical data generation in the 1.3-μm waveband. The insertion loss of the device can be compensated through the SOA, and we obtained an optical gain change of up to ~7 dB in the OGM section. Further, we successfully demonstrate a 10-Gb/s clear eye opening using the QD-OGM/SOA device with a clock-data recovery sequence at the receiver end. These results suggest that the monolithic QD-EOM/SOA is suitable for increasing the number of wavelength channels for smart short-range communications.

We have recently found that a long length of fiber of up to 1 km terminated with an in-fiber cavity structure can detect vibrations over a frequency range from 5 Hz to 2 kHz. We want to determine whether the sensor (including packaging) can be optimized to detect vibrations at even higher frequencies. The structure can be used as a distributed vibration sensor mounted on large motors and other rotating machines to capture the entire frequency spectrum of the associated vibration signals, and therefore, replace the many accelerometers, which add to maintenance cost. The sensor may also help detect in-slot vibrations which cause intermittent contact leading to sparking under high voltages inside air-cooled generators. However, that requires the sensor to detect frequencies associated with vibration sparking, ranging from 6 kHz to 15 kHz. Acoustic vibration monitoring may need sensing at even higher frequencies (30 kHz to 150 kHz) associated with partial discharge (PD) in generators and transformers. Detecting lower frequencies in the range 2 Hz to 200 Hz makes the sensor suitable for seismic studies and falls well into the vibrations associated with rotating machines. Another application of interest is corrosion detection in large re-enforced concrete structures by inserting the sensor along a long hole drilled around structures showing signs of corrosion. The frequency response for the proposed longgauge vibration sensor depends on packaging.

We report here flattened supercontinuum (SC) generated in tellurite-phosphate and chalcogenide-tellurite hybrid microstructured optical fibers (HMOFs) whose chromatic dispersion spectra are tailored with high freedom due to large refractive index difference (∆n) between the core and cladding glasses. It is shown in the simulation that the tellurite-phosphate HMOF whose chromatic dispersion spectrum is near-zero and flattened with three zero-dispersion wavelengths (ZDWs) over a wide wavelength range from 1000 to 4000 nm is beneficial to obtain broad and flattened SC spectra. By using a large ∆n of 0.49, the tellurite-phosphate HMOF which has flattened chromatic dispersion and three ZDWs is successfully fabricated. When a 20-cm-long tellurite-phosphate HMOF is pumped at 1550 nm with a 1560-W peak power, an SC extended from ~800 to 2400 nm where ~5-dB spectral flatness in the wavelength ranges from 890 to 1425 nm and from 1875 to 2400 nm (~1060-nm bandwidth in total) is observed. In addition, a flattened SC spectrum with ~6-dB spectral flatness over a broad wavelength range from 950 to 3350 nm (2400-nm bandwidth in total) is generated by pumping a 1-cm-long chalcogenide-tellurite HMOF at 2300 nm with a 40-MW peak power.

In this paper, the experimental investigation on the interaction length for getting the optimum diffraction of the multi-order acousto-optic diffraction is presented. Based on these results, the feasibility of acousto-optic Q-switch taking H₂O or TeO₂ as medium respectively for ultraviolet and visible lasers are discussed. The fact that the optimum interaction length tightly relies on the frequency of the sound and does not relate to the wavelength and power of the light is found in the experiment. The interaction length will become longer as the frequency of the ultrasound becomes higher. The interaction length is about 8mm when the acoustic frequency is at about 9MHz and becomes about 4mm at 6MHz. A Q-switch that works with pure water is designed and a total diffractive efficiency of about 98% was obtained under the condition that the acoustic frequency is 9MHz and the acoustic power is 3.4W. An acousto-optic Q-switch made of TeO₂, in terms of Raman-Nath diffraction is designed. With a cooling system on the device, a total diffractive efficiency of about 75% is obtained under the condition that the acoustic frequency is 10MHz and the acoustic power is 10W. The loss by one path of the device is about 5% on the best condition. Then the modulated pulse width is measured as about 200ns on the condition that the acoustic frequency is 11MHz, the acoustic power is 6W and the repetition frequency is 10kHz.

MgAl₂O₄ and ZnAl₂O₄ both have the spinel structure and similar lattice constants, but the bandgap of MgAl₂O₄ is about double that of ZnAl₂O₄, making it interesting to consider the mixed spinel (Mg_xZn_1-x)Al₂O₄ as a possible host for luminescent ions. Prior to preparing thin films, the Mg:Zn ratio and Tb concentration were optimized for green luminescence from the ⁵D₄ - ⁷F₅ transition of Tb³⁺ ions using nanocrystalline samples prepared by combustion synthesis. Thin films with x = 0.75 and 0.5 mol% Tb were spin-coated on Si(100) substrates using a solution of the nitrates of Mg, Zn, Al and Tb in ethanol, with ethylene glycol as complexing agent. Samples about 200 nm thick were obtained by sequentially depositing 10 layers at 3000 rpm for 30 s. Samples were annealed for 1 h in air before measuring their luminescence properties. For the sample annealed at 600 °C, x-ray diffraction showed the thin film had a strong (111) preferential orientation. Atomic force microscopy revealed a root means square roughness of 1 nm and Auger electron spectroscopy depth profiles showed a uniform layer with a sharp interface at the Si substrate. With an increase in annealing temperature up to 1000 °C, the luminescence increased while the surface became slightly rougher and the layer-substrate interface more interdiffused. Annealing the samples at 1200 °C resulted in diffusion of Si through the layer and the formation of an additional phase. While the green Tb emission was slightly reduced, blue emission from the ⁵D₃ level of Tb³⁺ was greatly enhanced in these samples.

In this paper we investigate optical properties and size distribution of the nano-colloids made of trivalent rare-earth ion doped fluorides: holmium and ytterbium, thulium and ytterbium, and erbium and ytterbium co-doped NaYF₄. These materials were synthesized by using simple co-precipitation synthetic method. The initially prepared micro-crystals had very weak or no visible upconversion fluorescence signals when being pumped with a 980-nm laser. The fluorescence intensity significantly increased after the crystals were annealed at a temperature of 400°C - 600°C undergoing the transition from cubic alpha to hexagonal beta phase of the fluoride host. Nano-colloids of the crystals were made in polar solvents using the laser ablation and ball milling methods. Size analyses of the prepared nano-colloids were conducted using a dynamic light scatterometer and atomic force microscope. The nano-colloids were filled in holey PCFs and their fluorescent properties were studied and the feasibility of new a type of fiber amplifier/laser was evaluated.

Photodoping phenomenon is observed when a double-layer consisting of an amorphous chalcogenide film (As₂S₃, GeS₂, GeSe₂ etc.) and a metal (Ag, Cu etc.) film is illuminated by light. The metal diffuses abnormally into the amorphous chalcogenide layer. Amorphous chalcogenide films of GeS₂ with an Ag over layer exhibited large increase of refractive index through the abnormal doping of Ag by irradiating the light around the absorption edge of the GeS₂ chalcogenide. In this study, we aimed the application of this effect for the fabrication of optical devices and fabricated various micro doped patterns by using a laser beam. Mask less pattering with refractive index modified films are possible by manipulating the scanning of the laser beam. Micro gratings were fabricated using a confocal laser microscope to work as both fabrication and observation system. Waveguides were also fabricated by scanning the laser beam for photodoping. Holographic gratings were fabricated by utilizing the photodoping of the two beam interference pattern, which showed the possibility to produce large scale optical devices or mass production.

Optical and electronic properties of monocrystalline silicon modified by ion implantation of silver (Ag+) at energy 75keV with different concentration: D1 = 10¹⁴ ion / sm², D₂ = 10¹⁵ ion / sm², D₃ = 10¹⁶ ion / sm² were investigated at room temperature used angularand spectral ellipsometry methods. While an experiment was carried out ellipsometry parameters Δ and ψ depends of angle of incidence (angular ellipsometry) and wavelengths (spectral ellipsometry). The refractive and absorption indexes, reflection index R(hν ) , permittivity ε (hν ) and optical conductivity σ ( hν ) were calculated using these parameters. The angular dependence of ellipsometric parameters was investigated using the serial ellipsometer LEF-3M-1 with the working wavelength 632,8 nm and a range of angles of incidence changes 65-80°. The samples' surface were explored across a broad spectral range λ=0,23 - 2,8nm (hv=0,44 - 5,39 eV) by the Beatty’s spectral ellipsometry method. In the work was compared the optical conductivity of pure Si and Si with different concentration Ag+. It is established that an increase in radiation dose observed a general shift of the bands in the direction lower energies. High intensity irradiation silver ions lead to a significant increase in surface roughness of single-crystal silicon, creating a large number of vacancies and may forms a further area at the bottom of the conduction band of silicon.

Efficient, easy and accurate tuning techniques to a plasmonic nano-filter are investigated. The proposed filter supports both blue and red shift in the resonance wavelength. By varying the refractive index with a very small change (in the order of 10^-3), the resonance wavelength can be controlled efficiently. Using Pockels material, an electrical tuning to the response of the filter is demonstrated. In addition, the behavior of the proposed filter can be controlled optically using Kerr material. A new approach of multi-stage electro-optic controlling is introduced. By cascading two stages and filling the first stage with pockels material and the second stage with kerr material, the output response of the second stage can be controlled by controlling the output response of the first stage electrically. Due to the sharp response of the proposed filter, 60nm shift in the resonance wavelength per 10 voltages is achieved. This nano-filter has compact size, low loss, sharp response and wide range of tunabilty which is highly demandable in many biological and sensing applications.

We present the broad and ultra-flat optical parametric gain in the highly nonlinear tellurite fibers with tailored chromatic dispersion. The effect of pump wavelengths and powers on dual-pump configuration of four-wave mixing (FWM) are investigated. It is clarified that an ultra-flat gain bandwidth with 658 nm and ±0.01 dB fluctuation can be achieved at the dual-pumping power of 1.25 W. Moreover, a gain bandwidth with 1524 nm and 60 dB signal gain with gain ripples can be obtained at the dual-pumping power of 3.0 W in 25 cm-long hybrid tellurite microstructured optical fiber.

A detailed model of the performance of a highly Yb³⁺/Er³⁺-codoped phosphate glass add-drop filter, which combines the propagation at resonance of both pump and signal powers inside the microring resonator with their interaction with the dopant ions, is used to analyze the requirements for gain/oscillation in these structures. Special attention is paid to the influence of additional coupling losses and asymmetry between the input/output couplers. It is concluded that, due to small signal gain saturation and the limited range of pump amplitude coupling coefficients, asymmetry does not greatly influence gain/oscillation requirements through the pump intensity build-up inside the ring. Asymmetry effect on small signal intensity transfer rate and threshold gain instead allows a significant lightening of the demanding doping ions concentrations requirements to achieve oscillation.

The luminescent properties of rare-earth doped solids have been under intense exploration for a wide range of applications ranging from displays and lasers to scintillators. In this work, the material purification, crystal growth, and spectroscopic properties of Ce³⁺-, and Eu³⁺- doped KPb₂Cl₅ as well as Pr³⁺ doped KPb₂Cl₅ and KPb₂Br₅ were investigated for possible applications in infrared lasers and radiation detectors. The studied materials were synthesized through careful purification of starting materials including multi-pass zone-refinement and halogination. The growth of the purified materials was then carried out through vertical or horizontal Bridgman technique. The trivalent praseodymium ion (Pr³⁺) offers a large number of laser transitions in the visible and infrared (IR) spectral regions. Using ~1.45 μm and 1.9 μm pumping, IR emissions at ~1.6, ~2.4, and ~4.6 μm were observed from Pr: KPb₂Cl₅ and Pr: KPb₂Br₅ corresponding to the 4f-4f transitions of ³F₄/³F₃→³H₄, ³F₂/³H₆→³H₄, and ³H₅→³H₄, respectively. Large emission cross-sections in the range of (4.8-6.1) x 10^-20 cm² (near-IR, ~1.6 μm) and (5.5-6.0) x 10^-20 cm² (mid-IR, ~4.6 μm) were observed for both crystals. Emission characteristics of the ~1.6 μm Pr³⁺ transition including IR to visible upconversion emission studies were also discussed. Under Xenon lamp excitation, preliminary spectroscopic results showed allowed 5d-4f Ce³⁺ emission centered at ~375 nm in Ce³⁺ doped KPb₂Cl₅. In addition, commercial Ce:YAG and Ce:YAP crystals are included in this study for comparison. Pr³⁺ and Eu²⁺ 5d-4f emissions were not observed from Pr³⁺/Eu²⁺ doped KPb₂Cl₅ crystals.

The third-order nonlinear susceptibility of crystalline Cadmium Magnesium Telluride (CdMgTe) was studies using a spatially resolved Irradiance Scan method including picosecond and nanosecond laser pulse widths at 1064nm. The samples were placed in a loosely focused beam, and a series of individual laser pulses at different energies were collected. The transmitted beam was reimaged to a CCD with a microscope objective providing a detailed objective function for numerical simulations. The nonlinear transmission results were modeled by way of a split-step nonlinear beam propagation method including diffraction, nonlinear absorption, and refraction arising from bound electrons and light-generated free carriers. The angular dependence of the third order susceptibility with respect to the electric field is also represented along with laser-induced damage thresholds.

Lately the demand for in situ and real time monitoring of industrial assets and processes has been dramatically increased. Although numerous sensing techniques have been proposed, only a small fraction can operate efficiently under harsh industrial environments. In this work the operational properties of a proposed photonic based chemical sensing scheme, capable to monitor the ageing process and the quality characteristics of coolants and lubricants in industrial heavy machinery for metal finishing processes is presented. The full spectroscopic characterization of different coolant liquids revealed that the ageing process is connected closely to the acidity/ pH value of coolants, despite the fact that the ageing process is quite complicated, affected by a number of environmental parameters such as the temperature, humidity and development of hazardous biological content as for example fungi. Efficient and low cost optical fiber sensors based on pH sensitive thin overlayers, are proposed and employed for the ageing monitoring. Active sol-gel based materials produced with various pH indicators like cresol red, bromophenol blue and chorophenol red in tetraethylorthosilicate (TEOS), were used for the production of those thin film sensitive layers deposited on polymer's and silica's large core and highly multimoded optical fibers. The optical characteristics, sensing performance and environmental robustness of those optical sensors are presented, extracting useful conclusions towards their use in industrial applications.

Nonlinear optical polymers show promising potential applications in photonics, for example, electro-optical devices. Poly (methyl methacrylate) (PMMA) is widely used in optical waveguides, integrated optics and optical fibers. However, PMMA has not been used for nonlinear optical waveguides since it has a low nonlinear refractive index. We successfully prepared chalcogenide amorphous nanoparticles doped PMMA that had a high nonlinearity. The As₃S₇ bulk glass was dissolved in propylamine to form a cluster solution. Then the As3S7/propylamine solution was added into methyl methacrylate (MMA) containing photoinitiator Irgacure 184 about 0.5 wt%. After well mixing the As₃S₇ nanoparticle doped MMA was transparent. Under the irradiation by a 365 nm UV lamp, As₃S₇ nanoparticles doped PMMA was obtained with yellow color. The third-order nonlinear optical susceptibility of As₃S₇ nanoparticles doped PMMA was investigated. An optical waveguide array based on the As₃S₇ nanoparticles doped PMMA composite of high nonlinearity was fabricated.

For both high conversion efficiency and thermal stability, glass-based phosphor-converted white light-emitting diodes (GBPC-WLEDs) were packaged for optic characterization study. Fabricated by flip chip, glass based PC-WLEDs were found Tj dramatically decreased, and emission intensity eminently raised up. If driven by large electric current, such samples would have even lower Tj 36°C. These characteristics will significantly improve thermal stability and lifetime of the LED packaging modules. In addition to high optical quality and low manufacture cost, such better thermal stability of glass phosphor layer may be beneficial for public policy of mass replacement of street lights with solid-state lighting LED as one of many applications requiring high-power and high reliability.