This PDF file contains the front matter associated with SPIE Proceedings Volume 11997, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

Subwavelength randomly nano-roughened interfaces have been shown to have polarization-insensitive, angle-ofincidence independent, broadband anti-reflective (AR) performance. The on-axis AR effect correlates with the nanoroughness longitudinal scale (depth), whereas feature transverse dimension distributions (average feature diameters) are responsible for diffracting (scattering) light. In cases where the surface RMS roughness parameter value approaches the incident radiation wavelength, diffuse scatter increases above axial transmission values. Random anti-reflective structured surface (rARSS) windows were fabricated to suppress axial reflectivity over the MWIR spectral band (3-5 μm) and transmission enhancement was confirmed via FTIR spectrophotometry. Using a polarized-laser scatterometer, bidirectional scattering distribution function (BSDF) of structured IR materials was measured using 3.39-μm-wavelength source at selected incidence angles over the equatorial plane of the unit sphere. Surface statistics of the roughened samples is correlated to the radiance distribution for assessment of surface-feature scattering effects.

In this work, we propose a plasmonic absorber structure composed of periodic gratings with hexagonal arrangements aided by rectangular metal-dielectric layers and PCM's (Phase Change Materials) in the infrared spectrum, between 1200-6000 nm, which has high optical contrast in these regions, thus favoring its use. The transition effects between the intermediate to amorphous and crystalline phases of the PCMs layers are analyzed, based on the LorentzLorenz relationship. Absorption effects can be controlled using functions in which geometric parameters and crystallization levels can be related. The results presented show high absorption above 95% in both phases of the material, in normal incidence. The physical mechanisms of absorption confinement were also investigated. These structures can offer great light coupling advantage in reconfigurable nanoplasmonic devices.

Quantum dots (QD) embedded in polymer matrix are a powerful material system for novel optoelectronic applications. Apart from the typical advantages available from QD systems such as size dependent optical properties and narrow emissions, they can also be used as a future multiplexed sensing device. In this work, we report optical emission from a two-color QD-doped silica and polymer system through photoluminescence measurements. The QD-based thin films could be excited through single wavelength in the visible range, and emitted at two distinct peaks with controllable intensities depending on the ratio of QDs doped into the silica and polymer. The emission increase of the two peaks as a function of excitation intensity was analyzed and compared with more traditional QD films deposited on bulk semiconductor substrates.

This paper presents the use of TiO₂ as a strip loaded waveguide on thin-film lithium niobate (TFLN). The waveguides were fabricated by using an RF reactive sputtering deposition followed by a dielectric lift-off process. An additional layer of SiO2 was deposited as a cladding layer using a plasma-enhanced chemical vapor deposition (PECVD). To characterize this process, atomic-force-microscopy (AFM) and an ellipsometer were used. Lastly, a propagation loss of 1.26dB/cm at 1550nm was experimentally measured by Optical Backscatter reflectometry (OBR) and are presented in this paper.

Perovskites doped with rare earth (RE) ions can be used to convert efficiently UV component of solar radiation spectrum in the near-infrared (NIR) radiation suitable for generating electricity in conventional silicon-based photovoltaic (PV) cells. These materials have good ability to capture the energy of the incident UV photons and transfer it to the embedded RE ions, such as Yb³⁺ emitting NIR photons. In this paper we explored two methods of synthesis of down-converting REdoped metal halide perovskites CsPbCl_xBr_1-x: Yb³⁺: the hot injection method of making nanoparticles (NP) and the two-stage spin-casting fabrication of the nano-films. The hot-injection method resulted in the NP with an average size varying from 4 to 120 nm. The XRD spectroscopy revealed that the synthesized NP had the crystalline structure like orthorhombic bulk crystal of CsPbBr3. The PL spectrum of the Yb³⁺ perovskite NP revealed the NIR PL peak at 980 nm attributed to the relaxation of the excited ion of Yb³⁺ and indicating that the process of spectral down-converting (quantum cutting) took place. Besides well-known dependence of the color of visible PL on the composition of the perovskite CsPbX3 (blue for X = Br, yellow – X = Cl, and red – X = I), we showed that the wavelength of the visible PL peak increases with the average size of the NP of CsPbCl_1.5Br_1.5. The nano-films of CsPbCl_xBr_1-x: Yb³⁺ prepared by the spin-casting method demonstrated visible PL of blue-green color. The obtained results might be of significance to the applications related to the efficient solar power and green power technology.

The future of photonic devices involves harnessing non-linear effects, for applications such as frequency upconversion and down-conversion, optical switching, and emission control. To effectively do this, the optical properties of designed material systems are needed. Hyperbolic metamaterials that use both conductors and dielectrics have been shown to have enhanced non-linear properties near the topological transition point. Creating that topological transition point in a layered hyperbolic metamaterial offers a way to control the non-linear properties without a complicated 3D design. Layered 1D metamaterials still have a large enough design space to achieve various non-linear effects across a large frequency range and have a relative ease of fabrication. For this research, ITO was chosen as the conductor, which has advantages due to its ready availability and CMOS compatibility. The chosen dielectric, SiO₂, is also easily available. The non-linear properties of the hyperbolic metamaterials were modeled with an efficient Matlab code, and the results show the capability of controlling the non-linear properties and optimizing for many different possible applications.

A shortwave infrared camera system with extended bandwidth of greater than 2 m and high resolution of 1.3 megapixels is demonstrated. The imager has a conventional p-i-n structure with type-II superlattice (T2SL) multi quantum well as the absorption region, and is backside illuminated to allow response to 400nm. The focal plane array is shown on both 8- and 12-µm pitches, with a wideband responsivity in a 0.4-2 µm range. New processing methodologies were developed and executed in a fabless model, achieving scalability, cost-efficiency, and high-performance metrics.

The optical detector used in pulsed LIDAR, range finding and optical time domain reflectometry systems is typically the limiting factor in the system’s sensitivity. It is well-known that an avalanche photodiode (APD) can be used to improve the signal to noise ratio over a PIN detector, however, APDs operating at the eye-safe wavelengths around 1550 nm are limited in sensitivity by high excess noise. The underlying issue is that the impact ionization coefficient of InAlAs and InP used as the avalanche region in current commercial APDs are very similar at high gain, leading to poor excess noise performance. Recently, we have demonstrated extremely low noise from an Al(Ga)AsSb PIN diode with highly dissimilar impact ionization coefficients due to electron dominated impact ionization. In this paper, we report on the first low noise InGaAs/AlGaAsSb separate absorption, grading and multiplication APDs operating at 1550 nm with extremely low excess noise factor of 1.93 at a gain of 10 and 2.94 at a gain of 20. Furthermore, the APD’s dark current density was measured to be 74.6 μA/cm² at a gain of 10 which is competitive with commercial devices. We discuss the impact of the excess noise, dark current and responsivity on the APDs sensitivity and, project a noise-equivalent power (NEP) below 80 fW/Hz^0.5 from a 230 μm diameter APD and commercial transimpedance amplifier (TIA). The prospects for the next generation of extremely low noise APDs for 1550 nm light detection are discussed.

Electrical crosstalk of in-device passivated mesa-based InGaAs photodetectors has been analyzed by a three-pixel mini array illuminated from the backside. In-device passivation of mesa-based lattice-matched InGaAs photodetectors significantly suppresses the surface-related component of dark current—however, inter-pixel crosstalk increases due to the depletion condition of the in-device passivation layer between the pixels. The inter-pixel crosstalk originates mainly from the high electric field in the in-device passivation layer. Here, in mesa-based in-device passivated InGaAs photodetectors, inter-pixel crosstalk has been significantly improved by adjusting the electric field distribution between the pixels with the inclusion of a thin n-InP crosstalk-block layer without affecting the primary purpose of the detector structure, which is strong resistivity to surface-related dark current increase.

A series of AlAsSb p⁺-i-n⁺ and n⁺-i-p⁺ diodes with varying i-region thickness from 0.08μm to 1.55μm have been used to determine the temperature dependent impact ionization coefficients by performing avalanche multiplication measurements from 210K to 335K. The increase in electron and hole ionization coefficients as the temperature decreases is much smaller when compared to InAlAs and InP. This leads to a much smaller avalanche breakdown variation of 13mV/K in a 1.55μm p⁺- i-n⁺ diode. For a 10Gb/s InGaAs/AlAsSb separate absorption and multiplication avalanche photodiode (SAM-APD), the variation in breakdown voltage is predicted to be only 15.58 mV/K.

Black silicon induced junction photodiodes have been shown to have nearly ideal responsivity across a wide range of wavelengths. Another important characteristic of a high-quality photodiode is rise time which can be used to approximate bandwidth of the photodiode. We show experimentally that the rise time of black silicon photodiodes is shorter than in planar photodiodes when alumina layer with similar charge is used to make an induced junction in both. Additionally, we show that the rise time can be rather well approximated using an analytical equation, which combines Elmore delay from equivalent circuit with standard RC-delay arising from series and load resistances.

Broadband and omnidirectional antireflection coatings in the 3-5 μm and 3-12 μm infrared ranges are of crucial importance in maximizing quantum efficiency in MWIR and LWIR photodetectors, as well as in improving the efficiency of LWIR thermophotovoltaic devices. Conventional approaches to AR coatings on semiconductors, such as quarter-wavelength optical thickness layers, fail to provide consistently high transmission over mid-IR bandwidths and acute angles of incidence. Unconventional approaches such as metasurface and nanostructure AR coatings are difficult and expensive to fabricate on a large scale. We discuss ultra-broadband antireflection coating designed through an inverse design procedure driven by a differential evolution optimization algorithm. Our approach iteratively simulates the transmission characteristics of a multilayer structure using the Transfer-Matrix Method and optimizes layer parameters to maximize the average transmission within a given wavelength band and range of angles of incidence. We present AR coatings which exhibit 98% and 96% average transmission over the 3 μm - 5 μm and 3 μm - 12 μm ranges respectively, over angles of incidence between 0° and 70°. Compared to quarter optical wavelength antireflection coatings over the same ranges, our structures exhibit significantly higher broadband transmission – quarter-wavelength structures saturate near 80% transmission over the 3-5 μm or 3-12 μm ranges, with transmission significantly lowered at large angles. As such, our results rival the transmission performance of state-of-the-art nanostructure AR coatings even at large angles of incidence but are significantly easier to fabricate using standard e-beam evaporation and/or sputtering.

Alternative way of synthesis for high refractive index tellurides based glasses has been experimented, in addition to low temperature Spark Plasma Sintering. The composition tested, Ge₂₅Se₁₀Te₆₅, has been chose in the Ge-Se-Te system and characterized. Its index refractive index of 3.12 and overall optical, thermal and mechanical properties makes it the perfect candidate for IR application. However, due to its relative instability regarding crystallization, formation of GeTe crystals occurs during mechanical alloying using raw elements. Transparency has not been achieved in the sintered samples using this powder, as the crystallization rate is accelerated by the pressure during the process. In parallel, glass samples synthesized by melt-quenching have been used to determine optimal sintering parameters for this composition. The main issue met during those tests has been the carbon contamination, reducing overall transparency of the samples through scatterings. As such, it has been shown that the critical parameter to consider to limiting this pollution is the powder granulometry, needing to be above 100μm for optimal performance. This shows the potential for this method to produce high refractive index IR optics, using even unstable glasses.

We report on the feasibility of MIL-101(Cr) (MIL: Materials of Institute Lavoisier) and MIL-101(Cr)-NH₂ as novel saturable absorbers for the development of passively Q-switched nanosecond mid-infrared fiber laser systems. The MIL101(Cr) and MIL-101(Cr)-NH₂ are prepared using hydrothermal synthesis method and their modulation depths are measured to be 24.09% and 22.83%, respectively. We employ them separately as SAs to achieve passively Q-switched fiber lasers operating at 2.8 μm, for the first time, to the best of our knowledge. Stable Q-switched pulse operation is realized with the shortest pulse duration of 0.75 μs at a repetition rate of 162.58 kHz when using MIL-101(Cr) as a SA. It generates the maximum average output power of 524.4 mW, pulse energy of 2.72 μJ and peak power of 3.43 W at the launched pump power of 3.64 W. In addition, we replace the MIL-101(Cr) with MIL-101(Cr)-NH₂ and nanosecond pulses with a pulse duration of 0.79 μs and average output power of 479.5 mW are obtained. The corresponding pulse energy and peak power are 2.27 μJ and 2.87 W, respectively. Our results show that the MIL-101(Cr) and MIL-101(Cr)- NH2 are promising stable SAs for nanosecond laser pulses generation at 3 μm.

Advanced radiation tolerant Erbium doped fibers have been developed surviving an accumulated dose of 1 kGy∗. Femtosecond fiber lasers and amplifiers manufactured from such fibers have been packaged and irradiated under active operation to test for accelerated ageing with dose rates up to 10 mGy/s using a Cobalt 60 source. The laser output power degraded by about 11% after exposure of a dose of 1 kGy. Compared to conventional Erbium fiber lasers this represents a significant improvement in radiation tolerance.

An innovative mid-infrared polarization-maintaining photonic crystal fiber (PM-PCF) with an asymmetric orthogonal pattern of longitudinal holes having different periods and diameters is presented. The PM-PCF is designed and made of chalcogenide glass to offer endlessly single mode in the mid-infrared (2-6μm) with good beam quality (M²~1). Most importantly, the guided mode is circular to improve the coupling efficiency and to perfectly collimate the output beam with a single lens. The large mode area enables the transmission of high-power polarized infrared laser (<10W CW). Also, the new PM-PCF has high birefringence (~10^-4), low propagation losses (0.2dB/m), and low insertion loss (<0.1dB). The PM-PCF preform is made by extrusion and is used to draw the mid-infrared PM-PCF. Simulation and experimental results on the mid-infrared PM-PCF are presented.

Random lasers (RLs) have been thoroughly studied for applications such as high definition speckle free imaging, lithography, miniature spectroscopy, etc. RLs made with crystalline powders have shown promising results, with high emission efficiencies and narrow wavelength bandwidth. However, few studies on glass random lasers have been made, since its inhomogeneous broadening make it hard to verify the linewidth narrowing characteristic of laser emission. Here, we describe linewidth and temporal measurements for a TZA glass doped with 16 wt% neodymium. We verified a 0.5 nm linewidth narrowing at laser threshold. The pump intensity where the transition occurs coincided with the appearance of a faster emission decay, showing the presence of laser emission for higher pump power energies. This result is promising in understanding random lasing for glass powders.

Geophysical applications of optical fibers for distributed temperature, strain, and acoustic sensing challenges their reliability due to harsh environmental conditions. Which may include high temperature, pressure, presence of hot steam, hydrogen, and other aggressive chemicals. Robustness of silica-based optical fibers is primarily governed by the thermal and environmental stability of their polymer coatings. Among different types of coatings, polyimide materials exhibit favorable properties, such as durability at elevated temperatures, protection against solvents, and long-term mechanical reliability. In this work we investigate optical fibers employed with a novel polyimide coating. Extensive environmental testing was performed, comparing fibers with a standard and the novel coating. Fiber samples were aged in dry air (up to 380 °C), high temperature/pressure water, paraffin oil, crude oil, hydrogen scavenging cable gel and isopropyl alcohol (all up to 300 °C/2000 psi). Mechanical strength of the aged fibers was used as a measure of their performance at harsh conditions. In addition, we studied an adhesion that develops at elevated temperatures between the fibers and a stainlesssteel tube interior. Thermal stability of the polyimides was also evaluated via thermogravimetric analysis. Based on the obtained results, the novel polyimide coating shows a 35 – 38 °C improvement over the standard coating. The findings indicate the superiority of the new coating, which should extend the useful temperature range for this class of optical fibers.

Raman fiber lasers are an excellent source for achieving high powers in wavelengths conventionally inaccessible with rare-earth-doped fiber lasers. In recent years, wavelength-tunable cascaded Raman lasers have been achieved using a Random Distributed Feedback Raman Fiber laser pumped in the 1micron wavelength band. Here, wavelength tuning is achieved using a combination of output power tuning for selecting different Stokes orders and tuning the wavelength of the pump source for output wavelength tuning around a specific Stokes order. In this approach, the feedback in the laser is broadband, and thus, the spectral purity and spectral linewidth of the output is severely compromised. There have been approaches to control the feedback using different filter architectures such as WDMs, Fabry-Perot filters, filter-fibers. Still, each has limitations in either the operating wavelength window or the spectral resolution. Here, we demonstrate a cascaded Raman laser comprising a reflective Fourier pulse shaper that provides near arbitrary feedback control. Our approach can enable wavelength and linewidth tunable lasers with a fixed wavelength pump. The pulse shaper operates over a wavelength region from 1.1 – 1.3micron, achieves spectral features as small as 0.5nm. The output of the cascaded Raman laser is over 10W, and the center wavelength can be selected from discrete lines at 1117nm, 1175nm, 1240nm with over 15nm of fine-tuning around each. The spectral purity of the output is <95% in all cases. The linewidth of the output is reduced to sub-nm levels and can be continuously tuned from 1-4nm by pulse shaper settings.

The chromatic dispersion in optical fibers is a key property for applications where a broadband light source is used and the timing of each individual wavelength is crucial. Counteracting the timing offset introduced by the fiber is a challenge in many applications especially in mode locked lasers. The dispersion parameters need to be measured with high precision. The length of the fiber, the temperature, and the used wavelength will highly impact the amount of dispersion and the accuracy of the measurement. We developed an ultra-high-accuracy dispersion measurement setup at 1080 ± 50 nm considering all the parameters that may influence the measurement. It is based on a home-built wavelength tunable laser where the output is modulated by an electro-optical modulator connected to a 24 GSamples/s arbitrary waveform generator to a complex pattern consisting of pulses and a 4 GHz sine wave. After passing through the fiber the signal is measured with an 80 GSamples/s real time oscilloscope. The fiber’s temperature is controlled to allow for reproducible measurements over several days and we achieve timing measurement accuracies down to ~200 fs. We also present the performance of the setup at ~850 nm. We will discuss and quantify all effects which can negatively impact the system accuracy and we will report on more cost-effective options using lower performance equipment.

The Pockels Cells play important role in generating helicity-flipping polarized laser beam to be used in high energy electron beam accelerator facility. Due to exceptional requirements for ultra-stable electron beam in modern nuclear physics experiment, the operation of Pockels Cells which are key components to generate stable electron beam becomes critical. However, since the operation of Pockels Cell, which usually work in pair, involves beam alignments up to 12 degrees of freedom, it requires extremely complicated controls to maintain the stable output beam through whole operation time of accelerator. In this paper, we combined the machine learning method with the Pockels Cells control system, automatically collected data of Pockels cells optical properties such as polarization extinction ratio (PER), beam position, optical intensity asymmetry, etc., at different orientation angles and physical potions, and built an artificial neural network which can determine the optimal position of Pockels Cells. The trained artificial neural network can predict the PER, intensity asymmetry, beam position difference with a mean agreement around 95%, which makes it possible to find the optimal yaw/pitch/roll angles and physical positions of the Pockels cells in a short time. This technology can also be translated to alignments of devices in other laser systems such as high energy ultrafast oscillators and amplifiers.

We present a study of nonlinearly governed all-optical switching of C-band femtosecond pulses using all-solid dual-core fibers with slight asymmetry between the cores. The fibers are made of a thermally matched pair of soft glasses ensuring high index contrast between the core and the cladding. Two dual-core fibers with lower and higher levels of dual-core asymmetry were examined by two different experimental approaches targeting nonlinear switching of 1560 nm, 75 fs solitonic pulses. When using the less asymmetric fiber, an effective self-switching of 1560 nm, 75 fs low-energy pulses was demonstrated; in the case of more asymmetric fiber, a cross-switching of identical pulses was achieved driven by 270 fs, 1030 nm control pulses. The fiber length was optimized in both cases by the cut-back method. The self-switching approach employed in the case of less asymmetric fiber resulted in 35 mm optimal length, at which the highest switching contrast of 20.1 dB with broadband character in the spectral range 1450-1650 nm was observed. The cross-switching in the more asymmetric fiber was performed with even higher switching contrasts exceeding 25 dB at more homogeneous spectral dynamics in the C-band at 14 mm optimal length. Both outcomes represent high application potential with some complementary advantages. The simpler self-switching scheme requires only a single sequence of pulses and subnanojoule switching energy levels. However, in applications where even higher switching contrasts are required, crossswitching can be performed by employing more complex experimental schemes with higher energy control pulses.

An optical sensor based on fiber Bragg grating (FBG) on a lithium noibate crystal substrate has been constructed and tested with excellent results for high-voltage sensing and measurement. The device is compact, reliable and easily reproducible. It has been tested in 2-14 kV environment, with variable humidity, and in its final configuration yielded repeatable and consistent results. Its construction is simple, robust and intended for field applications.

The mineral apatite and apatite-like compounds are a class of promising inorganic materials, reported to have a wide range of applications including, but not limited to, oxide fuel cells, phosphors, catalysis, and biomaterials. The mineral could be easily tuned via ionic substitutions for enhancement of various optoelectronic properties. In this study we report characterization of natural apatite crystals from different sources using optical spectroscopy, transmission electron microscopy, and X-ray diffraction. We also note roles of external factors such as high pressure and doping with rareearth elements on the optoelectronic properties of the mineral to explore alternate pathways for material synthesis and potential new applications.

Semiconductor quantum dots (QDs) have a wide absorption spectrum spreading from UV to the visible region and high photoluminescence (PL) quantum yield (QY) what determine possible use of their films for re-emitting coatings enhancing the photodetector spectral range. Unlike fluorescent organic dyes, the QDs absorption doesn’t saturate at high excitation intensities and can absorb more than one photon per particle due to the biexciton generation. However, due to the high rate of the Auger nonradiative relaxation, the QDs biexciton PL QY is much lower than the single-exciton one, what reduces the overall PL QY and the photodetector photosensitivity at the high excitation intensities. An employment of the Purcell effect in the plasmon nanocavities should increase the biexciton PL QY thus overcoming this limitation. To use this effect, we designed a thin-film plasmon–exciton material containing QDs and silver nanoplates (SNPs) in which the QDs’ PL band and the SNPs’ absorption band are overlapped. To demonstrate the advantage of the designed (QD-SNP)-film, we have compared effects of QD-film and (QD-SNP)-film on the photoresponse of the Si-based photodetector. The response of a photodetector to pulse excitation at 266 nm was negligible and increased after the deposition of the QD-film on its surface. However, at the high excitation intensities, the photosignal was reduced due to the biexcitons formation. The addition of SNPs increased the photoresponse at high excitation intensities. We attribute this improvement to a strong enhancement of QD biexciton PL in the QD-SNP material, which became predominate at high excitation intensities.

Fiber-based optical parametric amplification (FOPA) has been exploited for various applications due to its broad gain bandwidths and high signal gain in many spectral bands. By extending FOPA gain bandwidth towards the mid-infrared (MIR) region, more novel applications in spectroscopy, sensing, biology and so on are expected to be realized. However, highly efficient and stable FOPA performance is not easy to be obtained. It requires optical fibers with high nonlinearity, suitable control of chromatic dispersion and pump sources to satisfy the phase-matching condition which is the key for FWM process to occur. Among non-silica glasses, chalcogenide glasses have attracted great attention due to their very broad transmission window in MIR region and very high nonlinearity. For these reasons, this work is highly motivated to control and maintain the chromatic dispersion of chalcogenide optical fibers so as to achieve and maintain high-intensity and broad FOPA signal gain bandwidths in the MIR region by using an AsSe2 step-index optical fiber and a pump source near 5.0 μm. It is realized that by adding a chalcogenide buffer layer with appropriate refractive index and diameter to the conventional step-index structure, the performances of chromatic dispersion and FOPA can be improved and their fluctuation due to the change of fiber core can be greatly suppressed. As a result, a broad signal gain bandwidth from 3 to 14 μm at about 15 dB is attainable and can be maintained although the fiber core diameter drastically fluctuated from 2 to 5 μm.

A general approach for modeling the temperature dependence of optical absorptions in rare earth-doped crystals is presented and applied to transitions in Tm³⁺:YAG. The model allows for the generation of calculated absorption spectra at any temperature. There is close agreement between the model and measurements conducted of optical absorption in Tm³⁺:YAG for the ³F₃ and ³H₄ manifolds between 50 and 300 K. A model of the temperature variation of optical absorption features is highly useful in the design of high-powered solid-state laser systems. In addition, it is shown that absorption into Tm³⁺:YAG can be used as an optical thermometer at cryogenic temperatures. Absorption data as a function of wavelength and temperature was obtained for a sample of 1% Tm³⁺:YAG, which was mounted inside a cryostat with optical access. Broadband light from a tungsten-filament lamp passed through the crystal and entered a 0.25 m monochrometer and was detected with a photomultiplier tube. Transmitted light was analyzed for two spectral ranges: 650 - 725 nm which includes absorption into the ³F₃ manifold, and 750 – 825 nm which includes absorption into the ³H₄ manifold. The data was compared to a model for absorption cross sections that includes the temperature dependence of homogeneous broadening mechanisms and thermalization within the ground state Stark levels. This approach to modeling the temperature dependence of optical absorption should have general applicability for other rare earth-doped crystals.

In laser applications, unwanted transmission can require a beam dump positioned behind every mirror to prevent unwanted light propagation. Novel new mirrors (patent pending) based on an engineered substrate are able to reduce the power leaking through a component by several orders of magnitude while maintaining <98% of the reflective properties. Rated as both mirrors and neutral density filters, these parts greatly reduce the need for beam dumps behind components, minimizing the size of optical systems and improving laser safety. This paper will discuss the performance of these engineered mirrors and compare their reflection and transmission with traditional Fused Silica mirrors.

Many industrial processes currently require accurate and sensitive monitoring of CO₂ gas. To increase the sensitivity of CO₂ detection, open-air photonic fibers have been proposed. Open-air photonic fibers have a hollow core allowing the intercalation of gas into the fiber, allowing for the amplification of measurement techniques like absorption or Raman spectroscopy to detect CO₂ concentrations. We use conducted a variety of COMSOL based studies aimed at minimizing gas diffusion time throughout the hollow core. We investigate both pressure driven and diffusion based gas delivery methods, finding that both possess the ability to greatly reduce sensor response time. Preliminary experiments in a controlled environment validated the models and showed the ability to detect and control the uptake of CO₂ in open-air photonics fibers. This lays the foundation of a distributed chemical sensing system, particularly important for monitoring well integrity for carbon capture and storage, providing early warning for an incoming well failure and potential CO₂ leaking through it, potentially affecting proximal aquifers, a large public concern.

The development of extended range detectors based on InGaAs technology is a recent breakthrough in imaging. Taking advantage of the technological bricks developed for the C-RED 2 camera, First Light Imaging has integrated extended range InGaAs sensors and explored the possibilities offered by this technology. The C-RED 2 ER camera can support two detectors with shifted sensitivity. The cameras and their performances are described in detail in this paper. The C-RED 2 ER camera can operate with different readout modes and achieve high-speed frame processing to optimize the output image. The camera is capable of running at 600 full frames per second with image corrections applied. This is particularly relevant, as the lattice mismatch artefacts of the extended InGaAs technology can be a major drawback for its use in imaging and sensing applications. It is expected that the shifted spectral sensitivity of the C-RED 2 ER cameras will enable the development of systems dedicated to hyperspectral imaging, for waste sorting in particular. A proof of concept device based on a First Light Imaging camera was developed to demonstrate the performances of high-speed SWIR cameras when integrated in a push-broom type device. The result of this experiment is briefly reported in this paper.