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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Cavity-Resonator-Integrated Guided-Mode Resonance Filters for Compact WDM Light Source
摘要： A cavity-resonator-integrated guided-mode resonance filter (CRIGF) consists of a grating coupler (GC) integrated in a waveguide cavity resonator on a transparent substrate, and shows a narrowband reflection spectrum for an incident free-space wave of a small diameter. CRIGF of the waveguide cavity formed by two distributed Bragg reflectors (DBRs) of different reflectances is discussed. Such a CRIGF can act as not only a wavelength-selective reflector but also an input waveguide coupler. Integration of such CRIGFs for different wavelengths in a waveguide is proposed to give an array of external mirrors and a wavelength division multiplexer for constructing a compact multi-wavelength light source. Four CRIGFs of 10-μm-size aperture with a wavelength spacing of 15 nm were fabricated and characterized. CRIGF integrated on a reflective layer via an optical buffer layer is also discussed. Optimization of reflective and buffer layers is theoretically investigated to maximize a waveguide-coupled lasing power.
关键词： gratings,waveguides,wavelength multiplexers,external mirrors,guided-mode resonance,waveguide couplers,optical cavities,wavelength filters
更新于2025-09-19 17:15:36
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Brain Photobiomodulation—Preliminary Results from Regional Cerebral Oximetry and Thermal Imaging
摘要： A new piece of equipment for LED (light emitting diode) brain photobiomodulation is introduced. Preliminary results from regional cerebral oxygen saturation and from thermography are shown before, during and after stimulation. The procedure offers a new way to quantify the biological effects of a possible innovative therapeutic method. However further measurements are absolutely necessary.
关键词： stroke,brain,LED (light emitting diode) stimulation,photobiomodulation,regional cerebral oxygen saturation,LED helmet,mental diseases,light therapy,wavelength,dementia,thermal imaging
更新于2025-09-19 17:15:36
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Carrier reduction studies of type-II superlattice materials for very long wavelength infrared sensing
摘要： There are continuing efforts to develop type-II superlattice (SL) materials for very long wavelength infrared (VLWIR) detector applications. However, the SLs have high residual electron background doping densities that depend on SL growth conditions, which lead to shorter minority carrier lifetime and lower performance parameters than theoretically predicted. In this study, the authors compare the technical advantages of using InAs/GaInSb over InAs/GaSb SL with respect to reducing the electron doping levels. Our temperature-dependent electrical transport measurements show that the InAs/GaInSb SL design has a lower electron density than the InAs/GaSb SL with the same bandgap and have electron densities (mobilities) on the order of the mid 1011 cm?2 (25 000 cm2/V s). Since small period InAs/GaInSb SLs also produce greater Auger recombination suppression for a given VLWIR gap than the large period InAs/GaSb SL, the InAs/GaInSb SL appears to be a better candidate for long lifetime IR materials for future very long wavelength infrared devices.
关键词： very long wavelength infrared,mobility,InAs/GaSb,Auger recombination,InAs/GaInSb,type-II superlattice,carrier reduction,electron doping
更新于2025-09-19 17:15:36
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Photopolymerization of the coumarin-containing reversible photo-responsive materials based on the wavelength selectivity
摘要： Photo-response of the coumarin derivative based on the reversible photodimerization and photocleavage has been studied for long time. This paper reports a novel approach of preparing photo-responsive polymer materials containing coumarin structure by photopolymerization based on the wavelength selectivity. A photo-polymerizable and photo-responsive monomer 7-(hydroxyethoxy)-4-methyl-coumarin (AECM) was synthesized and performed photo polymerization upon UV light irradiation (λ=405 nm). After polymerization the polymer with coumarin pendant groups can achieve reversible photoinduced [2+2] dimerization under UV light (λ>300 nm) and the photo-cleavage of crosslink to recovery back to the original structure through further irradiation with UV light (λ=254 nm). What’s more, this monomer could be used to produce high-resolution pattern and photo responsive pressure sensitive adhesive through photopolymerization. The demonstrated approach opens new perspectives for the design of photo-response materials.
关键词： coumarin,photopolymerization,photo-response,wavelength selectivity
更新于2025-09-19 17:15:36
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Bifunctional Etalon-Electrode to Realize High Performance Color Filter Free Image Sensor
摘要： Organic photodiodes (OPDs), based on organic semiconductors with high absorption coefficients for visible light, are emerging as potential candidates for replacing silicon photodiodes in image sensors, particularly due to the possibility of realizing a thin thickness and exclusion of color filters, both of which can contribute to a dramatically enhanced degree of integration for image sensors. Despite years of research, techniques have not yet been developed that allow the OPD itself to have color selectivity while maintaining a thin (<1 μm) OPD thickness, in combination with a sufficiently high detectivity (>1012 cm?Hz0.5/W). To solve this issue, we introduce a concept of 'etalon-electrode', which can perform the function of electrode, and simultaneously the function of selective wavelength transparency. A strategically designed OPD architecture consisting of an etalon-electrode, a panchromatic organic active layer, and a counter electrode displays well-defined narrowband R-/G-/B-selective detectivity spectra depending on precision-adjusted thickness composition of the etalon-electrode. While a thin thickness of OPD is preserved at less than 800 nm including electrodes, active layer and other buffer layers for all R-/G-/B-selective OPDs, high average detectivity values over 1012 cm?Hz0.5/W are demonstrated. Furthermore, the characteristic of imparting color selectivity by the etalon-electrode enables a more facile full color patterning, such that a prototype of a 10×10 image sensor with a pixel pitch of 500 μm is realized, resulting in accurate picturing of a well-defined full color image.
关键词： high detectivity,organic photodiodes,etalon-electrodes,full-color imaging,color filter free,image sensor,wavelength selectivity
更新于2025-09-19 17:15:36
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Equidistant combination wavelength screening and step-by-step phase-out method for the near-infrared spectroscopic analysis of serum urea nitrogen
摘要： We applied near-infrared (NIR) spectroscopy with chemometrics for the rapid and reagent-free analysis of serum urea nitrogen (SUN). The modeling is based on the average effect of multiple sample partitions to achieve parameter selection with stability. A multiparameter optimization platform with Norris derivative filter–partial least squares (Norris-PLS) was developed to select the most suitable mode (d = 2, s = 33, g = 15). Using equidistant combination PLS (EC-PLS) with four parameters (initial wavelength I, number of wavelengths N, number of wavelength gaps G and latent variables LV), we performed wavelength screening after eliminating high-absorption wavebands. The optimal EC-PLS parameters were I = 1228 nm, N = 26, G = 16 and LV = 12. The root-mean-square error (SEP), correlation coefficient (RP) for prediction and ratio of performance-to-deviation (RPD) for validation were 1.03 mmol L?1, 0.992 and 7.6, respectively. We proposed the wavelength step-by-step phase-out PLS (WSP-PLS) to remove redundant wavelengths in the top 100 EC-PLS models with improved prediction performance. The combination of 19 wavelengths was identified as the optimal model for SUN. The SEP, RP and RPD in validation were 1.01 mmol L?1, 0.992 and 7.7, respectively. The prediction effect and wavelength complexity were better than those of EC-PLS. Our results showed that NIR spectroscopy combined with the EC-PLS and WSP-PLS methods enabled the high-precision analysis of SUN. WSP-PLS is a secondary optimization method that can further optimize any wavelength model obtained through other continuous or discrete strategies to establish a simple and better model.
关键词： wavelength step-by-step phase-out,near-infrared spectroscopic analysis,equidistant combination wavelength screening,Serum urea nitrogen,Norris derivative filter
更新于2025-09-19 17:13:59
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Switchable dual-wavelength mode-locked fiber laser using Saganc loop mirror
摘要： We report an all-fiber switchable dual-wavelength mode-locked laser using a Sagnac loop mirror. In this laser, the Sagnac loop mirror acts as a tunable periodic filter, in which the wavelength spacing is determined by the length of the polarization maintaining fiber. With appropriate pump power, the mode-locked fiber laser can operate in both the tunable single-wavelength mode locking regime and the dual-wavelength mode locking regime by properly setting the states of the polarization controllers. In the single-wavelength mode locking regime, the laser achieves continuously tunable wavelength range from ～1551 nm to ～1562 nm. In the dual-wavelength mode locking regime, the laser can emit two stable asynchronous pulse trains with the central wavelengths of 1561.4 nm and 1551.1 nm, respectively. Due to the net negative dispersion of the laser cavity, the mode-locked pulse trains with different central wavelengths have different group velocities leading to a repetition rate difference of ～530 Hz.
关键词： Tunable wavelength,Dual-wavelength,Sagnac loop mirror,Mode-locked fiber laser
更新于2025-09-19 17:13:59
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InGaAs Membrane Waveguide: A Promising Platform for Monolithic Integrated Mid-Infrared Optical Gas Sensor
摘要： Mid-infrared (mid-IR) absorption spectroscopy based on integrated photonic circuits has shown great promise in trace-gas sensing applications in which the mid-IR radiation directly interacts with the targeted analyte. In this paper, considering monolithic integrated circuits with quantum cascade lasers (QCLs) and quantum cascade detectors (QCDs), the InGaAs-InP platform is chosen to fabricate passive waveguide gas-sensing devices. Fully suspended InGaAs waveguide devices with holey photonic crystal waveguides (HPCWs) and sub-wavelength grating cladding waveguides (SWWs) are designed and fabricated for mid-infrared sensing at λ=6.15μm in the low index contrast InGaAs-InP platform. We experimentally detect 5 ppm ammonia with a 1 mm long suspended HPCW and separately with a 3 mm long suspended SWW, with propagation losses of 39.1 dB/cm and 4.1 dB/cm, respectively. Furthermore, based on the Beer-Lambert infrared absorption law and the experimental results of discrete components, we estimated the minimum detectable gas concentration of 84 ppb from a QCL/QCD integrated SWW sensor. To the best of our knowledge, this is the first demonstration of suspended InGaAs membrane waveguides in the InGaAs-InP platform at such a long wavelength with gas sensing results. Also, this result emphasizes the advantage of SWWs to reduce the total transmission loss and the size of the fully integrated device’s footprint by virtue of its low propagation loss and TM mode compatibility in comparison to HPCWs. This study enables the possibility of monolithic integration of quantum cascade devices with TM-polarized characteristics and passive waveguide sensing devices for on-chip mid-IR absorption spectroscopy.
关键词： sub-wavelength waveguides,gas sensing,absorption spectroscopy,photonic crystal waveguides,mid-infrared,photonics integrated circuits,quantum cascade devices,parts-per-billion
更新于2025-09-19 17:13:59
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Dynamic Control of Transparent Optical Networks with Adaptive State-Value Assessment Enabled by Reinforcement Learning
摘要： For efficient and dynamic path operations in transparent optical networks, routing and wavelength assignment (RWA) must be optimized in terms of not only link-resource utilization but also traffic distribution. In this paper, we propose a reinforcement-learning-based RWA algorithm that maximizes the number of paths to be accommodated to a network with pre-training using estimated traffic distributions. Numerical experiments elucidate that the number of paths accommodated increases by up to 9.1%.
关键词： transparent optical network,network-state value,reinforcement learning,routing and wavelength assignment,dynamic network control
更新于2025-09-19 17:13:59
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[IEEE 2018 7th International Conference on Reliability, Infocom Technologies and Optimization (Trends and Future Directions) (ICRITO) - Noida, India (2018.8.29-2018.8.31)] 2018 7th International Conference on Reliability, Infocom Technologies and Optimization (Trends and Future Directions) (ICRITO) - Analyzing the Internal Parameters of Free Space Optical Communication
摘要： Free Space Optical (FSO) Communication is an efficient technology as it offers higher signal bandwidth and less power for transmission. There are some internal parameters on which the performance of the FSO communication depends such as beam divergence, wavelength. The purpose is to optimize these factors to achieve the maximum output and throughput. In this paper FSO model has been designed using PIN Photodiode and Avalanche Photodiode(APD) at receiver’s side. Using the model, Q-Factor has been estimated for different beam divergences and wavelengths at varying bit rates. The results have been compared and analyzed for the two types of photodiodes.
关键词： wavelength,FSO,Beam divergence,Avalanche Photodiode,PIN,Q-Factor
更新于2025-09-19 17:13:59