- 标题
- 摘要
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- 实验方案
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Alternative approach to optimizing optical spacer layer thickness in solar cell using evolutionary algorithm
摘要： This work is inspired by Darwin's biological evolution theory: natural selection. We propose to use genetic evolutionary algorithm to optimize the search for the optimal thickness in solar cells with regards to maximizing short-circuit current density. Optical spacer layer thickness need to be optimized in order to achieve maximum absorption of the incoming light by the solar cell. In order to obtain the best optical spacer thickness, we perform multiple simulations with different number of population, number of generations, mutation probability, number of bits, and selection and crossover methods. Our preliminary experiments show that the introduction of evolutionary algorithm result in a satisfactorily accurate search method when compared to brute-force. The future works on utilizing the full ability of evolutionary algorithm will be presented at the conference.
关键词： finite difference time domain,evolutionary algorithm,organic solar cell,optical modelling
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Inhomogeneous Broadening of a Polaritonic Mode in the Ultrastrong Coupling Regime
摘要： Ultrastrong coupling (USC) regime has been an intriguing research topic in cavity quantum electrodynamics (QED) experiments due to its capability to modify the ground and the excited states of a coupled system[1-3]. We investigate the USC of Landau level (LL) transitions in a two dimensional electron gas to teraherz (THz) metasurfaces using THz time domain spectroscopy. Complementary THz split ring resonator (cSRR) arrays are used as metasurfaces[4]. A higher coupling rate can be achieved by reducing the capacitive gap of the resonator due to the increased vacuum ?eld ?uctuations. However, our results indicate that this reduction introduces an inhomogenous broadening of the upper polariton branch below a threshold gap width.
关键词： complementary split ring resonator,Ultrastrong coupling,Landau level transitions,THz time domain spectroscopy,THz metasurfaces
更新于2025-09-12 10:27:22
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[IEEE 2019 7th International Conference on Information, Communication and Networks (ICICN) - Macao, Macao (2019.4.24-2019.4.26)] 2019 7th International Conference on Information, Communication and Networks (ICICN) - High-Sensitivity Plasmonics Biosensor Based on Graphene Ribbon Arrays
摘要： A finite-difference-time-domain (FDTD) approach was undertaken to investigate the extraordinary optical transmission (EOT) phenomenon of graphene ribbon arrays deposited on a silica substrate for refractive index (RI) sensing. The numerical investigation shows that the choice of chemical potentials and its layer’s number of graphene will affect the sensitivity enhancement. The critical parameters of graphene ribbon arrays including the duty ratio, as well as its period, which affect the EOT and RI sensitivity for the sensor, are discussed and optimized. It is demonstrated that a high average sensitivity of 2900 nm per refractive index unit (RIU) is achieved for the dip wavelength interrogation. The averaged figure of merit (FOM) of the proposed sensor is calculated to be 10 RIU-1. Our findings hold potential applications in designing a high-performance plasmonic biosensor.
关键词： surface plasmon resonance,finite-difference time-domain,periodic ribbon arrays,plasmonics biosensor,graphene
更新于2025-09-12 10:27:22
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Impact of silver nanogratings for enhanced light absorption in plasmonic based photodetector
摘要： Recent era has witnessed a wide interest of researchers for the development of nano scale high speed photodetectors. Now days, optical communication systems demand these detectors with light enhancement along with high gain and bandwidth. Plasmonics based photodetectors with gold nanogratings are employed in literature for high responsivity and miniaturization. However, these devices need to be explored for other metals as gold being very costly. In this work, plasmonic based photodetector is designed with silver nanogratings and analyzed over varying shapes like rectangular, trapezoidal, ellipse and parabolic taper. Enhanced light absorption with quenching factor of 73.96% is achieved with rectangular grooves in near infrared region as compared to other shapes.
关键词： Surface plasmons (SPs),Absorption,Nano gratings,Enhancement,Plasmonic,Photo-detectors,Subwavelength aperture,Finite-difference,Time-domain (FDTD) simulation
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Time Domain Traveling Wave Model of a Hybrid Laser for Silicon Photonics Applications
摘要： Integration of lasers sources in Silicon Photonics (SiPh), realised trough different techniques, became very appealing for applications in the ever growing field of intra/inter chip data data interconnects and optical communications. We implemented a Time Domain Traveling Wave (TDTW) model based on a set of Partial Differential Equations (PDE) for the slowly varying envelope of the electric field, the medium polarization and the charge carriers density in order to describe the dynamics of a new generation of hybrid laser based on III-V Reflective Semiconductor Optical Amplifier (RSOA) and SiPh external mirror with narrow effective reflectivity bandwidth (< 10GHz) similar to that considered in [2, 3]. The effect of the SiPh mirror can be taken into account by cascading the transmission matrices associated with all its passive sections (namely spot-size-conveter, phase control sections, ring resonators etc...) and including the result in frequency dependent boundary conditions for the PDE problem. Differently from standard rate equation models for semiconductor lasers, our approch correctly reproduce the RSOA gain/refractive index dependence from frequency and carriers density that represent peculiar features of radiation-matter interaction in semiconductor media and play a fundamental role in determining the hybrid laser dynamical behaviour. After computing the TW (Traveling wave) solutions for typical narrow reflectivity bandwidth designs, we numerically showed how for realistic values of the linewidth enhancement factor α (namely α > 2) stable single frequency lasing emission not always occurs at the reflectivity peak (TW0 solution in Fig. 1), but on the red part of the SiPh mirror reflectivity resonance curve around the point of maximum reflectivity slope (TW1 solution in Fig. 1a and Fig. 1b). The fact that this point also coincides with that of minimum optical linewidth, where negative feedback regime reduces instantaneous frequencies fluctuations, and the additional numerical evidence that the interval of TW stability decreases with increasing output power indicate that phase-amplitude coupling mediated by the α-factor may be at the origin of the observed TW instability. It also follows that by a suitable tuning of a phase section in SiPh circuit it is possible to stabilize hybrid laser emission by placing a TW solution on the point of maximum reflectivity slope.
关键词： hybrid laser,Partial Differential Equations,linewidth enhancement factor,Silicon Photonics,Time Domain Traveling Wave model,Reflective Semiconductor Optical Amplifier
更新于2025-09-12 10:27:22
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Enhanced terahertz radiation of photoconductive antenna fabricated on GaAs-on-sapphire
摘要： The terahertz (THz) radiation properties of a photoconductive antenna (PCA) fabricated on a GaAs-on-sapphire (GoS) substrate are reported at sub-THz band. The GaAs layer with a thickness of approximately 1 μm was directly deposited on a sapphire wafer by means of molecular beam epitaxy. A butterfly-shaped antenna structure was then fabricated on the GoS substrate by photolithography, and the device was tested as the emitter of an in-house built THz time-domain spectrometer. The performance of this antenna was compared with a commercial one, which had an identical antenna structure but was fabricated on low-temperature-grown GaAs (LT-GaAs). The results showed that the GoS-based PCA radiated an enhanced THz field, which could be as much as 1.9 times that of the LT-GaAs-based PCA, indicating that GoS could be a promising photoconductive material. In addition, the optical transparency of the sapphire substrate allows the device to be illuminated from the backside, which is crucial for THz near-field imaging applications where the sample is usually in close proximity to the front surface of the PCA device.
关键词： photoconductive antenna,molecular beam epitaxy,THz time-domain spectrometer,terahertz,GaAs-on-sapphire
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - DSTMS-Based Ultrabroadband Terahertz Time-Domain Spectroscopy
摘要： DSTMS organic electro-optic crystal is a very promising and efficient THz-wave generation material. It allows for both very high THz electric fields generation, exceeding several GV/m using optical rectification of femtosecond laser pulses, as well as the possibility for extremely broad bandwidth extending well beyond 10 THz. However, the usual laboratory THz systems based on these crystals exploit very bulky and expensive fs laser systems, which are not desired for industrial THz imaging and spectroscopy applications. Recently, some compact system employing organic crystals were demonstrated, however they use a conventional photoconductive antenna as a THz-wave detector. Here we present a compact THz time-domain spectroscopy system based on a relatively low-cost and small-size femtosecond fiber lasers operating at 1560 nm. As the THz generation and detection material, we choose the organic crystal DSTMS (4-N,N-dimethylamino-4’-N’-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate), since it reaches the highest overall efficiency and the flattest spectrum among the presently known state-of-the-art organic crystals. The developed terahertz system is capable of achieving frequencies up to 20 THz with a high dynamic range of more than 60 dB. We use a commercial femtosecond laser with pulse length of 18 fs, 200 mW average power, 40 MHz repetition rate and 1560 nm wavelength as pump beam. We achieve a very large frequency bandwidth reaching 20 THz, profiting from using DSTMS as both THz generator and THz coherent detector material.
关键词： DSTMS,organic crystal,terahertz time-domain spectroscopy,THz-wave generation,femtosecond fiber lasers
更新于2025-09-12 10:27:22
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Folded chaotic whispering-gallery modes in nonconvex, waveguide-coupled planar optical microresonators
摘要： Chaotic whispering-gallery modes have significance both for optical applications and for our understanding of the interplay between wave phenomena and the classical ray limit in the presence of chaotic dynamics and openness. In strongly nonconvex geometries, a theorem by Mather rules out the existence of invariant curves in phase space corresponding to rays circulating in whispering-gallery patterns, so that no corresponding modes of this type are expected. Here, we discuss numerical computations of the electromagnetic fields in planar dielectric cavities that are strongly nonconvex because they are coupled to waveguides. We find a family of special states which retains many features of the chaotic whispering-gallery modes known from convex shapes: An intensity pattern corresponding to near-grazing incidence along extended parts of the boundary, and comparatively high-cavity Q factors. The modes are folded into a figure-eight pattern, so overlap with the boundary is reduced in the region of self-intersection. The modes combine the phenomenology of chaotic whispering-gallery modes with an important technological advantage: The ability to directly attach waveguides without spoiling the Q factor of the folded mode. Using both a boundary-integral method and the finite-difference time-domain technique, we explore the dependence of the phenomenon on wavelength in relation to cavity size, refractive-index contrast to the surrounding medium, and the degree of shape deformation. A feature that distinguishes folded from regular whispering-gallery modes is that a given shape will support high-Q folded chaotic whispering-gallery modes only in certain wavelength windows.
关键词： chaotic whispering-gallery modes,finite-difference time-domain technique,nonconvex geometries,waveguide-coupled planar optical microresonators,boundary-integral method
更新于2025-09-12 10:27:22
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Luminescence lifetime encoding in time-domain flow cytometry
摘要： Time-resolved flow cytometry represents an alternative to commonly applied spectral or intensity multiplexing in bioanalytics. At present, the vast majority of the reports on this topic focuses on phase-domain techniques and specific applications. In this report, we present a flow cytometry platform with time-resolved detection based on a compact setup and straightforward time-domain measurements utilizing lifetime-encoded beads with lifetimes in the nanosecond range. We provide general assessment of time-domain flow cytometry and discuss the concept of this platform to address achievable resolution limits, data analysis, and requirements on suitable encoding dyes. Experimental data are complemented by numerical calculations on photon count numbers and impact of noise and measurement time on the obtained lifetime values.
关键词： lifetime-encoded beads,multiplexing,Time-resolved flow cytometry,bioanalytics,time-domain measurements
更新于2025-09-11 14:15:04
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Computer Aided Patterning Design for Self-Assembled Microsphere Lithography (SA-MSL)
摘要： In this paper, we use a finite difference time domain solver to simulate the near field optical properties of self-assembled microsphere arrays when exposed to an incoherent light source. Such arrays are typically used for microsphere lithography where each sphere acts as a ball lens, focusing ultraviolet light into an underlying photoresist layer. it is well known that arrays of circular features can be patterned using this technique. However, here, our simulations show that additional nanometer scale features can be introduced to the pattern by optimising the sphere dimensions and exposure conditions. these features are shown to arise from the contact points between the microspheres which produce paths for light leakage. for hexagonally close packed arrays, the six points of contact lead to star shapes in the photoresist. These star shapes have subfeature sizes comparable to the current achievable resolution of low-cost fabrication techniques.
关键词： finite difference time domain solver,microsphere arrays,SA-MSL,photoresist,Self-assembled microsphere lithography
更新于2025-09-11 14:15:04