This PDF file contains the front matter associated with SPIE Proceedings Volume 11682

The investigation of the doping level influence and p-n junction location in the barrier photodetector with InGaAS/AlInAs on InP was carried out. The detectivity value is determined by the differential resistance and it is related to the photosensitive layer doping level. I t was detected that the differential resistance is decreased due to doping. At the same time the peal detectivity can be reached at lower voltage. The barriers and contact layers thicknesses optimization are the important tools for quantum efficiency optimization.

Carrier lifetime characterization in solar cell and light emitting diode materials by time-resolved photoluminescence and differential transmission is of high importance, indicating cost-efficient streak camera suitable for such tests would be highly demanded. In this work an electro-optic deflecting device is extended to full functionality streak camera operating in wide spectral range (200-2000 nm) by using electro-optic DKDP crystals. Setup, consisting of picosecond laser for sample excitation, electro-optic deflector and imaging spectrograph with silicon and InGaAs cameras, allows spectral and temporal imaging of recombination dynamics in semiconductor materials, with variable bandgap and composition (tested on metal-halide perovskite crystal), achieving temporal resolution up to 50 ps. For the case of time-resolved differential transmission, broadband <50 ps pulsed or CW xenon light source can be used for absorption change probing.

A novel approach for coherent detection with double-side vertically illuminated photodetectors is presented. Signal and local oscillator (LO) are injected collinearly from opposite sides of the photodetector chip. As a result, no optical combiners are required and the concept inherently provides angular selective detection, as the relative angle between signal and LO has a strong influence on the generated RF power. These properties can be exploited for developing compact, solid-state receiver modules in single-channel and arrayed configurations for different sensing and imaging applications, e.g., coherent light detection and ranging (LiDAR).

A high-quality photodiode has high signal-to-noise ratio (SNR), which is ultimately defined by the responsivity and dark current of the photodiode. Black silicon induced junction photodiodes have been shown to have nearly ideal responsivity across a wide range of wavelengths between 175-1100 nm at room temperature (RT). Here we present their spectral responsivity stability and dark current at different temperatures. Both quantities show temperature dependencies similar to conventional pn-junction photodiodes, proving that black silicon photodiodes maintain their improved SNR also at temperatures other than RT.

Tunable mid-wave infrared (MWIR) filters are highly desirable in a wide variety of imaging and spectroscopic applications; with the waveband containing numerous invaluable spectral absorption signatures. We demonstrate spectrally-tunable, all solid-state, thin-film bandpass filters operating across the MWIR by utilizing the phase-change material (PCM) Ge2Sb2Te5 as a tunable cavity medium between two Bragg mirrors. The induced PCM refractive index modulation increases the cavity’s optical path length, thereby tuning the filter passband. Our filters have 300 nm spectral tunability, ~70% transmission efficiencies, and ~60 nm passbands. We further show multispectral thermal imaging and dynamic CO2 gas plume sensing using the filters.

In this paper we present a novel configuration for an all-fiber tunable infinite impulse response (IIR) optical filter using stimulated Brillouin scattering. By applying the Brillouin acoustic waves within the coupling area of an optical coupler, we can control its transmittivity and so to affect the spectral response of the IIR optical filter. In this paper we explain the principle of operation of the proposed device and experimentally demonstrate the ability to control the spectral response of an optical filter based on fiber ring resonator configuration. We presented preliminary experimental results which demonstrate the potential of the proposed method for the realization of a tunable optical filter, by achieving a change of about 0.7 dB in the depth of the spectral response of the filter. Such device could be used for realization of many allfiber optical components such as modulators and switches. In future work, an improvement of the filter may be realized, by using the short loop configuration, and a narrower laser source for the input signal.

The article gives two examples of the incorporation of liquid phase coated low refractive index (RI) and high refractive index materials in a proof-of-concept optical devices. Using ultra low RI (1.25) and ultra high RI (2.05), a 12-layer dielectric mirror is constructed. Optical properties of the stack are compared against to simulations, and a SEM-image of the stack is provided. The second example of using of high RI/low RI materials is provided where UV-curable, high RI material (1.9) nanoimprint material is nanopatterned, followed by gap-fill and protections by a cover glass using a dual cure (UV+thermal) RI 1.4 low refractive index bonding adhesive.

Various optical phenomena and techniques have been used to encrypt sensitive data and detect counterfeit objects. When two multilayer dielectric films of different indices are deposited in an alternating pattern on a glass substrate to form an optical filter, the transmission of this filter presents an optical spectrum. Because of the two materials’ different indices, layer sequences, and number of layers, the spectrum of any one of these filters is unique and exclusive. The spectrum and corresponding multilayer structure, therefore, can be considered a spectrum “fingerprint” and can be used to encrypt confidential information. One can design a multilayer sequenced layer structure as an encryption code. Knowing the spectrum of this code, they can also design a decryption filter to analyze the code spectrum and access the information embedded in the encrypted filter. High and low index materials Ta2O5 and SiO2 were used to fabricate multilayer film stacks with around 5 to 10 high-low pairs. The spectrum has multiple peaks in the visible wavelength range and is designed such that the spectrum appears colorless. A decryption multilayer film would block all but one of the peaks, the transmission of which would reveal the color. In this study, we present how we can design an encryption and decryption spectrum, how one can use these spectrum “fingerprints” to store confidential information and, when necessary, access said information by placing a decryption filter above the encryption filter.

Periodic gratings with complex shapes are designed by machine learning as emitters for a thermophotovoltaic system with a GaSb photovoltaic absorber operating at 1000K in order to maximize thermophotovoltaic efficiency. We also demonstrate complex-shaped GaN grating VCSEL mirrors designed by machine learning for high reflectivity and a wide stopband with center wavelength of 500nm. The results obtained indicate a 50% increase in stopbandwidth for the complex-shaped grating over that of a rectangular grating.

A new type of double cladding optical fiber has been demonstrated utilizing a GRIN MM inner cladding and an SM core to allow DTS, DSTS and DAS within a single optical fiber. DAS and DTS results are experimentally proven possible with this novel fiber design.

For several years, chalcogenide glasses have been studied as good candidates for numerous applications in the midinfrared region. Indeed, these glasses are transparent from 1 to 20 μm (depending on the composition), a mid- IR windows well-suited for sensing molecules whose optical signatures are located in the 2-16 μm range. In addition, thanks to appropriate thermal properties, chalcogenide glasses can be drawn into fibers, including microstructured optical fibers. In this work, a new method based on 3D-printing process is investigated to produce hollow chalcogenide glass preforms, which are then drawn into hollow-core fibers. The transmission of the “printed” hollow-core fiber has been measured and compared to the initial glass. A significant, but still manageable, increase by a factor of 2.5 is observed. This works opens a promising way for the fabrication of chalcogenide MOFs, more particularly for the elaboration of hollow core fibers.

The miniaturization of optical fiber polarization beam splitters (PBS) is highly desired, especially in optical communications. Here, we demonstrate the first-ever PBS based on Photonic Crystal Fibers (PCFs). The device is enabled by high-resolution 3D printing based on two-photon lithography, a method that grants unprecedented design flexibility to realize PCF segments with arbitrary geometries. The PCF-PBS is composed of three segments, for a total length of 210 µm, and is directly printed in a single step on a single-mode fiber. The PCF-PBS has an extinction ratio greater than 10 dB on a 100 nm bandwidth centered at around 1550 nm.

Super-PDMS with solvent dispersibility promises flexible PDMS-based waveguides in both the cladding and the core. The PDMS can fabricate a micro ~ submicron scale structure easily like waveguide by wet process, as oppose to conventional PDMS which uses imprinting to create microstructures. The refractive index of the PDMS is about 0.1 higher than that of conventional one. Super PDMS solutions dispersed in 1,2 dichloroethane solvent maintained transparent crystals in spontaneous drying after drawing, even at a high concentration of 15 wt.%. A flexible PDMS waveguide with a conventional PDMS cladding and a super PDMS core propagated light even with a waveguide bend radius of 2.5 mm, which is smaller than the minimum bend radius of a typical optical fiber.

Sapphire single crystal fibers have shown great potential in fiber-based high temperature sensing applications. As single crystals are grown without cladding, there have been a lot of different techniques that have been proposed to achieve a core-clad structured fiber. A common approach is to achieve this is by using sol-gel deposition where the cladding layer is grown on a crystal fiber via dip-coating and subsequent thermally treatment. In this work we describe the synthesis of magnesium aluminate spinel via sol-gel methods and application of it as a cladding material for sapphire crystal fibers. The thermal stability of spinel coatings on sapphire substrates is investigated as the formation of non-stoichiometric spinel at high temperature is well-documented. Sapphire fibers with the spinel cladding layers are tested under different gas atmosphere at elevated temperatures, to demonstrate the efficacy of spinel as a cladding layer.

We present an improved CMOS-compatible USRN material prepared using DCS-based chemistry deposited at a low temperature of ~300°C. Morphology and composition of these USRN films are characterized using SEM, TEM, EDS and AFM. Surface profilometer is also used to estimate the film stress over an 8-inch wafer. TEM shows that the USRN film is amorphous and AFM measures a low roughness RMS of ~0.4 nm over a scan window of 3 μm x 3 μm. Optical properties of these USRN films are studied using variable-angle spectroscopic ellipsometry and FTIR spectroscopy. A prism coupler is used to estimate the film propagation loss. Ellipsometry measurement shows refractive index of around 3.09 at 1550 nm wavelength, which is our wavelength of interest. Comparing with USRN films prepared using SiH_4- based chemistry, FTIR characterization shows reduced absorbance for films prepared using DCS-based chemistry at wavenumber region where Si-H bonds are located. The absorbance caused by N-H bonds are comparable for USRN films prepared using both DCS-based and SiH_4-based chemistries. Si-H bonds and N-H bonds are expected to be the main sources of material absorption near 1550 nm in the USRN material. Characterization results of waveguides fabricated using USRN deposited by this DCS-based chemistry shows propagation loss of ~4.9 dB/cm for waveguide width of 1.5 μm at 1550 nm wavelength. The improved results of DCS-based USRN will help to further cut losses and therefore enhance the performance of CMOS compatible USRN devices in nonlinear signal processing.

In the pursuit of new mid-IR laser gain materials, dysprosium-doped barium fluoride was evaluated for its potential laser emission in the 3-μm spectral region. Comprehensive spectroscopic characterization was performed, including absorption, fluorescence, and decay-time measurements. Efforts to determine the discrete Stark splittings of various Dy3+ manifolds in this host material were hampered by apparent multisite behavior of the RE dopant. Laser-relevant parameters such as absorption and stimulated-emission cross sections, quantum-efficiencies, and radiative lifetimes were determined for room temperature (300 K) and cryogenic temperature (77 K). The gain cross sections, which predict overall laser performance, were also calculated. Room-temperature laser operation of the 3-μm transition would suffer from low quantum efficiency and would require a high population inversion of approximately 40%. The parameters at 77 K show improvement across the board with multiple-times-higher cross-section intensities, nearly 4× higher quantum efficiency, and a positive gain cross section requiring less than 20% population inversion.

Solid-state laser based on Er-doped gain medium, is a promising approach to designing directly diode-pumped eye-safer pulsed sources in the spectral range ~1.45-1.65 m. This approach allows obtaining spectrally broad laser outputs with high efficiency, if required by application (e.g., anti-speckle), without resorting to nonlinear conversions. All-fiber laser solutions for high PRF pulsed laser sources is deemed desirable, but it may result in high design complexity, especially on the Master Oscillator (MO) end, hence it is not appropriate in cases where low complexity is of major importance. Presented here are the results obtained with pulsed hybrid MOPA comprised of a bulk crystalline Er-based MO and Er-doped fiber amplifier.

Swept-source lasers are key components of the modern spectral-domain Optical Coherence Tomography (OCT) systems. Further progress of OCT technology requires swept-source lasers working at specific, application dependent, wavelength, which are also compact and low-cost. In this work, we report the development of a low cost, compact, semiconductor swept-source laser based on slots etched along the ridge. The laser consists of a central gain section, phase section, semiconductor-optical-amplifier (SOA) sections and mirror sections employing higher-order gratings. The design and optimization of different parameters of the laser structure such as ridge width/depth, slot width/depth, no. of slots and so on are performed before the fabrication process. The main aim in the design step was to ensure single mode operation while maximizing the tuning range. The above optimization is performed keeping in mind the narrow linewidth of the emission spectra and minimum laser length. Due to the nature of the surface gratings, this type of laser does not require any complex regrowth and expensive e-beam lithography steps during fabrication. The slot and ridge sections of the laser are etched in a single wafer process step and the laser is also monolithically integrable with other system components. Initial measurements have indicated the high quality of the slot geometry and stable single mode operation with high side mode suppression ratio (SMSR) of 25 dB. The full-scale development of this laser will allow increasing resolution and imaging depth of OCT systems.

As already done in electronics, passive and active photonic devices demand integration on flexible substrates for a broad spectrum of application ranging from optical interconnection to sensors for civil infrastructure and environments, to coherent and uncoherent light sources and functionalized coatings for integration on biological tissue. In this communication we will present some recent results concerning the fabrication of novel flexible optical layers by sol-gel and radio frequency sputtering deposition techniques. The perspective is to give a technological way to transform intrinsically rigid or brittle materials into a highly mechanically flexible and optically functional systems

The mid-infrared fluorescence properties of erbium (Er) doped low-phonon ternary chloride-based crystals (KPb₂Cl₅, Cs₂HfCl₆, CsPbCl₃, CsCdCl₃) have been investigated. All crystals were grown by vertical Bridgman technique. Following optical excitations at 805 nm and 660 nm, all Er³⁺ doped chlorides exhibited infrared emissions at ~2750, ~3500, and ~4500 nm at room temperature. The mid-infrared emission at 4500 nm originating from the ⁴I_9/2 → ⁴I_11/2 transition showed long emission lifetime values of ~7.8 ms and ~11.6 ms for Er³⁺ doped Cs₂HfCl₆ and CsCdCl₃ crystals, respectively. In comparison, Er³⁺ doped KPb₂Cl₅ and CsPbCl₃ demonstrated shorter lifetimes of ~3 ms and ~1.8 ms, respectively. The temperature dependence of the ⁴I_9/2 decay times was performed for Er³⁺ doped CsPbCl₃ and CsCdCl₃ crystals. We observed that the fluorescence lifetimes were nearly independent of the temperature, indicating a negligibly small non-radiative decay rate through multiphonon relaxation, as predicted by the energy gap law for low phonon energy hosts. The room temperature stimulated emission cross-sections for the ⁴I_9/2 → ⁴I_11/2 transition were determined to be in a range of ~0.14-0.54 x 10^-20 cm² for the studied Er doped chloride crystals.

This work presents an innovative screen-printed anti-counterfeiting strategy based on highly Yb3+ doped Sr/Zr hybrid oxides photothermal particles that activate thermochromic pigment. The distinctive photothermal quality can be attributed to the low thermal conductivity of host, the high amount of doping, and the low emission efficiency, the latter being verified employing a theoretical model based on rate equations. The proposed system presents a high level of security since, after several testing such as excitation at different wavelengths and powers or under a pure source of heat, decoding process is limited to only one 975 nm fixed power laser diode.

In this article we have studied the structure of Au-Pd core-shell nanoparticles, which is composed of a uniform Au inner core surrounded by Pd nanoparticles. This is done to a new ultrasensitive sensor with height performance characteristics, low-cost fabrication process for hydrogen detection. Hydrogen cannot be used like any other gas because of its explosive behavior at 4% concentration in the air and, to avoid any risk we need to control its concentration permanently. The Au– Pd core-shell nanoparticles (NPs) were synthesized according to a multi-reduction step method. The morphology, density, size, and structure of these nanoparticles can be controlled by the synthesis conditions. They were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The impact of Pd shell on the surface plasmon resonance (SPR) was investigated by finite difference time domain simulations (FDTD) and the absorption spectroscopy under different hydrogen concentrations ranging from 1% to 4%. We noticed a change in the optical behaviour and a shift of the SPR peak of our Au-Pd core-shell system towards the lowest wavelengths from the first hydrogenation dehydrogenation cycle.

Due to their exibility, highly transparent silicone materials offer potentials for the development of adjustable optics. Previously realized mechanisms for changing the focal length of a solid silicone lens applied discrete points of force to mechanically deform the geometry. This article describes an approach to adjust the focal length of silicone lenses quickly and precisely. The chosen approach aims for a minimal number of moving components to provide reliability and reduced complexity. A contactless and stepless adjustment is realized by using electromagnetic control. To determine the functionality of the lens, the tunable range of the focal length will be investigated.

Light emission from PbS quantum dots (QDs) is an intriguing topic from application perspectives, and even after myriad of articles, still has open questions. The paper highlights the optical characterization of PbS QDs deposited via solvent deposition on semi-insulating GaAs substrates. The QD thin films were characterized by two-photon excited photoluminescence (TPL) measurements, exciting the samples with increasing pulsed laser (1064 nm, 10 Hz, 26 ps) intensities. The work reveals alterations of the optical properties of GaAs when hetero-paired with PbS QDs, as demonstrated by the trend of the TPL peak increase, the energy where the TPL peak takes place, and the overall dynamics of the peak shift. We also report that the TPL intensity increase of PbS QDs shows the same trend as the single-photon excited emission, and observed photo-induced doping of the QDs, i.e., the dynamic Burstein-Moss blue shift. The work stresses the possibility to modify the optical properties of semiconductor hosts by means of heteropairing with QDs. Through this work, we further attempt to reconcile observations, which are much different from reported classical models in semiconductor heterostructures.

We present studies on bioactive silica-based glass nanoparticles showing photoluminescence. The sol–gel or solvothermal route was used for syntheses. Lanthanides, zinc oxide or phthalocyanine complexes ensured light emission. The structural, morphological, and optical properties were examined. During the bioactivity tests, when particles were immersed in SBF, ions release to the medium and hydroxyapatite formation were analyzed. Composites with graphite oxide were described as well. The systems are promissing for monitoring structural changes of the glass immersed in biological fluids, bioimaging or photodynamic therapy. Research was performed within Polish–Ukrainian Joint Exchange Project and NSC grants 2016/23/B/ST5/024830, 2016/22/E/ST5/00530.

We engineer the nonlinear response of multilayered hyperbolic metamaterials systems by employing the optical response of Arsenide semiconductor materials. The photoexcited carriers lead to spectral, temporal, and polarization dependent optical response that is described in this talk. The response is suggestive of generating a transient hyperbolic materials response in this system. Exploration of this response and the use of these materials as a basis for nonlinear metasurfaces will be discussed.

We demonstrate an electrically tunable metasurface from an array of nanoresonators coated by a single layer of electro-optic molecules that are embedded in a polymer matrix. By periodic poling of the non-linear coating in plane, we tune the resonant frequency of the array under an applied bias at high speeds and over a broad range in the near-infrared.

In this study, we present a joint theoretical and experimental study on the dielectric permittivity of ultra-thin TiN films of varying thicknesses. We perform both ex situ and in situ ellipsometry to decouple the effects of thickness and oxidation. Our results indicate a remarkably persistent plasmonic character as the thickness is reduced. The effects of thickness and oxidation on their plasmonic properties are analyzed as fundamental parameters to optimize the optical response. Atomically thin plasmonic materials display great potential for the realization of tailorable and dynamically tunable metasurfaces because of their large sensitivity to structural parameters and external perturbations.

Combination of carbon-based nanomaterials (CNMs) with AuNPs has been demonstrated to enhance the LSPR response and facilitate the functionalization with specific and selective antibodies. Also, the introduction of CNMs in the plasmonic layer allows tuning of the LSPR central frequency. Joining the double dependence of the LSPR on the MNPs size and the presence of CNMs, it is possible to create a set of plasmonic layers whose LSPR wavelengths are distributed in a spectral range of few tenth of nanometers. This consideration paves the way to an LSPR sensor with an arrayed structure, where each element maximizes its specific LSPR at its own wavelength. Illumination with a broad light source produces a different response in each one of the elements. The working process underlying the sensing operation is that each element of the sensor array acts like a band-stop optical filter for a specific wavelength. The output can be extracted by the application of an image analysis approach to the spatially modulated light crossing the sensor area, based on a color recognition algorithm. A change in the refractive index over the sensor array will shift the rejection band of the sensing elements. An automatized method for color recognition can support the analysis of the refractive index variations yielding the final sensor output. A figure of merit, highlighting the LSPR central wavelength and spectral extension for different LSPR configurations, is also obtained for different sizes of the AuNPs and different flavors of CNMs.

Superresolution phase pupil filters (SRPF) are diffractive optical elements used to direct coherent laser light to spot sizes below the diffraction limit, at the expense of an exponentially reduced Strehl ratio. They can be fabricated as binary or multiphase elements, and have varying transverse-feature pixel dimensions. Because of the wide range of pixel sizes and groupings, ranging from possibly 100’s of microns to submicron, anti-reflection thin-film layered coatings are difficult to implement on SRPF topography without impacting the filter’s phase-distribution function and overall performance efficiency. SRPF elements were implemented on fused silica wafers using standard microlithography, to produce laser beam spots below 50% of the nominal diffraction-limited diameter (Airy spot). Anti-reflection random nano-structures (rARSS) were added on the SRPF substrate surface to enhance the component’s transmittance by reducing Fresnel reflectivity. The SRPF were tested at three laser wavelengths: 543 nm, 594 nm, and 633 nm, using a CCD 2D-array beam profiler before adding the random nanostructures, in order to validate design performance, as well as, after adding rARSS, to quantify transmission enhancement and the impact on beam spot quality and size. An overall reflectance suppression was measured in the illumination pattern, and the superresolution beam spot was not affected by the presence of the rARSS.

Randomly nano-roughened interfaces between optical media can result in polarization-insensitive, angle-of-incidence independent, broadband anti-reflective (AR) performance. The on-axis AR effect correlates with the nano-roughness longitudinal scale (depth), whereas feature transverse dimension distributions (average feature diameters) cause selective scatter. Subwavelength, random AR structured surfaces (rARSS) can forward scatter light in the transmission direction, suppress specular Fresnel reflectivity, and enhance overall axial transmission throughput. In cases where the random nanoroughness average value approaches that of the incident radiation wavelength, the induced scatter can be detrimental to imaging applications due to uniformly distributing light from the specular into wider angles, reducing image contrast and broadening (blurring) the axial image spot. Using a polarized-laser scatterometer, we measured the bidirectional scattering distribution function (BSDF) of nano-roughened fused silica (FS) windows and compared them to an optical-quality FS flat and two different flat mirrors. The fabricated rARSS windows were optimized to have a broadband, anti-reflective specular response (R<1%) in the visible spectral range (>400 nm). The BSDF was measured at 633-nm-wavelength, over the equatorial plane of the unit sphere, and at selected incidence angles below Brewster’s value. Granulometry of the roughened surfaces is correlated with the scattering data, for assessment of roughness-induced scattering effect. Using the BSDF data, single-surface and double-surface rARSS-treated windows were evaluated to determine any surface-to-surface scatter cascading effects.

Single crystal fibers have shown great potential for harsh environment sensing applications. Interrogation schemes based on temperature dependence of Raman scattering modes in crystals, offer capability of sensing at high temperatures. Yttrium aluminum garnet (YAG) is a potential alternate to sapphire as it also has similar material properties like high melting point and chemical resistance. In this work, Raman scattering in YAG samples have been measured from room temperature to 1000°C. Temperature dependence of the peak position, and peak width are measured and compared for the different peaks. A Raman based Optical time domain reflectometry (OTDR) is constructed and distributed temperature measurements of a furnace are conducted using a YAG crystal fiber.

We have developed a near-infrared spectral sensor chip capable of classifying different materials and quantifying their composition. The core device consists of an array of pixels having distinct spectral responses covering the 900-1700 nm wavelength region. Each pixel consists of a resonant-enhanced photodetector comprising an absorbing layer and a tuning element embedded in a vertical cavity. The chip is based on a III-V/Silicon hybrid technology and enables easy customization of the wavelength response and high responsivity. Its robustness, small dimensions and single-shot operation make this sensor suitable for portable spectroscopic applications in the agro-food sector.

We experimentally demonstrate a reflective long period grating based temperature sensor with a temperature sensitivity coefficient of 0.046 nm/°C in the range between 23°C and 200°C. Compared to traditional metal coating methods, such as evaporation, we used a cost-effective brush coating method to coat silver on both the end facet and a 60cm long tail end of the fiber beyond a long period grating (LPG) to realize a reflection mode LPG. The measured optical spectrum of the fabricated reflective LPG completely mimics the transmitted spectrum with reduced intensity. This cost-effective method for coating metal will pave the way for inexpensive LPG and other optical fiber sensor manufacturing and widespread utilization.

The application in polarization sensor systems uses changes in the polarization of light in the optical fiber during temperature changes. The principle of operation consists in the specific propagation of polarized light by special optical fibers, which, thanks to their construction, keep the light in two axes, but change the speed of their propagation and thus the instantaneous state of light polarization. It has been shown that by suitable methods it is possible to transform changes in the polarization of light into changes in its intensity, which can be detected very efficiently and quickly by a photodiode. This method has been practically verified, implemented by fiber components and confirmed as suitable for the implementation of a fiber sensor of thermal field disturbance. However, it turns out that especially in military and biomedical applications it is impossible to place a source of optical radiation close to the measured subject and the sensor must be powered remotely using optical fibers of the order of kilometers. This paper shows the possibility of using long optical paths to power the polarization sensor.

Spectroscopic characteristics of the lower lying energy levels of Pr3+ doped into the low-phonon energy hosts CsPbCl3 and TlPb2Br5 were explored for mid-IR laser applications. Both crystals posses relatively large IR absorption cross-sections for their 3F4+3F3 and 3F2+3H6 excited states, which indicates efficient optical pumping at either ~1.5 µm and ~2.0 µm, respectively. Pr: TlPb2Br5 exhibited an efficient MIR emission at room temperature with a lifetime of ~37 ms making it a promising candidate for laser applications. Only weak MIR emission was observed from Pr: CsPbCl3 due to strong emission quenching. More details of the IR spectroscopy including temperature dependent spectral and lifetime studies will be presented at the conference.

Highly doped with ytterbium (up to 20 wt% of Yb₂O₃) Er-Yb aliminosilicate glass core fibers have been fabricated and thoroughly investigated. It has been discovered that in a particular condition the lasing properties of both Yb and Er ions can be nearly completely suppressed. Due to a very high Yb ions absorption in the 900-1000 nm range (~ 3000 dB/m at 915 nm) all together with low background losses the developed glass matrix is very promising for such applications as pump isolation in fiber lasers as well as spectral and mode filtering using highly absorbing glass dopants.

Fiber optical parametric amplifiers (FOPAs) have attracted much attention than conventional optical amplifiers due to their wider operating wavelength ranges. By expanding the FOPA gain bandwidth towards the mid-infrared region, which can only be obtained by using highly nonlinear chalcogenide fibers, more interesting applications in spectroscopy, sensing, biology and metrology can be realized. Chalcogenide hybrid microstructured optical fibers (chalco HMOFs) with buffer layer demonstrated by our group showed good FOPA performance from 3 to 10 μm. However, their tiny and symmetric structures of air holes are difficult to fabricate. To overcome, chalcogenide all solid HMOFs (chalco ASHMOFs) with 6 low-index rods in the cladding were studied in this work using As₂Se₃, AsSe₂ and As₂S₅ glasses. Moreover, to obtain high birefringence which is necessary to minimize detrimental effects such as, polarization mode dispersion, polarization noise and instability and polarization-maintaining, the symmetry of the fiber was broken by enlarging a pair of solid rods. Numerical analyses show that chalco ASHMOFs can provide near-zero and flattened chromatic dispersion (<10 ps/km.nm) from 5 to about 12 μm and the phase birefringence can be as high as 4.4 x10^-3 at 14 μm. When a pump of 5 W at 4890 nm is coupled to a 3-cm-long section of the chalco ASHMOF, 16-dB signal gain can be obtained from about 3 to 12 μm which is equal to 9000-nm FOPA gain bandwidth in the mid-infrared. Compared to the 6500-nm gain bandwidth obtained from the previous chalco HMOF, novel chalco ASHMOFs are very potential candidates of FOPA devices in the mid-infrared region.

A novel UV transparent visible scattering spectroscopic material based on refractive index matching by dispersing specific CaF₂ particles into the PDMS matrix was proposed. This hybrid material can be used to develop a UV bandpass filter that showed high transmittance around 260-280 nm and wider bandwidth in the UV region. Furthermore, micro-CaF2 particle size with narrower size distribution that can be fabricated by grinding, precipitation, and centrifugal separation, showed narrower bandwidth of transmittance spectra after dispersing in the PDMS matrix.

Manganese doped inorganic halide perovskites continue to be of current interest for applications in light emitting devices and down-converters in solar cells. In this work we prepared Mn doped CsPbCl₃ (Mn: CPC) bulk crystals and nano-particles (NPs) and compared their emission properties. Bulk crystals were grown from the melt by vertical Bridgman technique and NPs were synthesized using a microwave assisted method. Under ultraviolet excitation at 350 nm, bulk crystal and NPs exhibited a broad orange emission centered in the ~600 nm range at room temperature. The broadband emission was assigned to the intra-3d transition ⁴T₁ → ⁶A₁ of Mn²⁺ ions incorporated in the CPC host lattice. The Mn²⁺ emission lifetimes were nearly exponential with values of 1.1 ms for NPs and 0.7 ms for the bulk crystal. NPs also showed exciton emission peaking at ~402 nm, whereas the bulk crystal exhibited no emission near the band-edge. Instead, the bulk material revealed a weak below-gap emission in the 450-550 nm region suggesting the existence of defect states. The excitation spectra for the orange Mn²⁺ emission from NPs and bulk crystals of Mn: CPC were significantly different indicating distinct excitation pathways. The excitation spectrum of the orange Mn²⁺ emission from NPs showed excitonic structure similar to the absorption spectrum suggesting an efficient energy transfer from excitons to Mn²⁺ ions. In contrast, UV excitation was less efficient for the bulk crystal and the excitation was dominated by below-gap excitation bands centered at 427 and 500 nm.

A CW signal experiences a time-varying gain when it co-propagates with pulsed pump in a semiconductor optical amplifier (SOA) due to cross gain modulation, and this can be used to experimentally measure gain recovery time. In this study, we establish a linear relation between the measured gain recovery time and the carrier lifetime of SOAs through detailed numerical simulations of a cross-gain modulated system. The small signal gain and the saturation power are determined experimentally. We also study the dependence of gain recovery time on the pump pulse widths which are smaller than the carrier lifetime and on the CW power. These studies help in an accurate estimation of carrier lifetime of a packaged SOA device.

This paper describes two different designs of 1×128 passive optical splitters for telecommunication applications. The first splitter consists of cascade arranged directional waveguide branches (Y-branch splitter) with a standard waveguide core size (6x6) μm². The second splitter is based on multimode interference occurring in a large MMI coupler, which uses a self-imaging effect for beam propagation, exhibiting the same waveguide core size as a Y-branch splitter. The waveguide channel profile, used in both approaches, is based on a standard silica-on-silicon material platform, with refractive index of core being n_c = 1.456 and a refractive index of cladding n_cl = 1.445. The splitters are designed and simulated at a telecommunication operating wavelength, λ = 1550 nm. Except for the lengths of the used Y-branches and MMI coupler, design parameters such as port pitch between the waveguides and simulation parameters for all splitters are considered fixed. Design, simulation, and optimization of passive optical components are performed by a commercial photonic software tool BeamPROP from Optiwave, which uses the Beam Propagation Method. This work aims to find the minimum physical dimensions of the designed splitters with a satisfactory optical performance. According to the minimum insertion loss and minimum non-uniformity, the optimum length of the splitters is determined. Finally, the optical properties of splitters for both approaches are discussed and compared with each other.