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Pulsation Characteristics of Jovian Infrared Northern Aurora Observed by the Subaru IRCS with Adaptive Optics
摘要： We report narrow band-?ltered imaging observations of the Jovian H3+ 3.4-μm emission using the IRCS (infrared camera and spectrograph) on the Subaru telescope taken on 25 May 2016. Approximately 1 hr of data was taken at intervals of 45–110 s, with high spatial resolution (~0.2 arcsec) using adaptive optics. In the northern polar region, we found bright patch-like emissions on the poleward side of the main oval. One of them had a pulsation period of ~10 min. We utilized an H3+ emission model to investigate the response time of the H3+ emission to abrupt and periodic variations of the precipitating electron ?ux. The model showed that the H3+ emission could pulsate with this timescale due to a modulated ?ux of the precipitating electrons in the kilo-electron-volt to tens of kilo-electron-volt energy range.
关键词： adaptive optics,H3+,Subaru telescope,infrared emission,Jovian aurora
更新于2025-09-10 09:29:36
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Wave-optics uncertainty propagation and regression-based bias model in GNSS radio occultation bending angle retrievals
摘要： A new reference occultation processing system (rOPS) will include a Global Navigation Satellite System (GNSS) radio occultation (RO) retrieval chain with integrated uncertainty propagation. In this paper, we focus on wave-optics bending angle (BA) retrieval in the lower troposphere and introduce (1) an empirically estimated boundary layer bias (BLB) model then employed to reduce the systematic uncertainty of excess phases and bending angles in about the lowest 2 km of the troposphere and (2) the estimation of (residual) systematic uncertainties and their propagation together with random uncertainties from excess phase to bending angle profiles. Our BLB model describes the estimated bias of the excess phase transferred from the estimated bias of the bending angle, for which the model is built, informed by analyzing refractivity fluctuation statistics shown to induce such biases. The model is derived from regression analysis using a large ensemble of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO observations and concurrent European Centre for Medium-Range Weather Forecasts (ECMWF) analysis fields. It is formulated in terms of predictors and adaptive functions (powers and cross products of predictors), where we use six main predictors derived from observations: impact altitude, latitude, bending angle and its standard deviation, canonical transform (CT) amplitude, and its fluctuation index. Based on an ensemble of test days, independent of the days of data used for the regression analysis to establish the BLB model, we find the model very effective for bias reduction and capable of reducing bending angle and corresponding refractivity biases by about a factor of 5. The estimated residual systematic uncertainty, after the BLB profile subtraction, is lower bounded by the uncertainty from the (indirect) use of ECMWF analysis fields but is significantly lower than the systematic uncertainty without BLB correction. The systematic and random uncertainties are propagated from excess phase to bending angle profiles, using a perturbation approach and the wave-optical method recently introduced by Gorbunov and Kirchengast (2015), starting with estimated excess phase uncertainties. The results are encouraging and this uncertainty propagation approach combined with BLB correction enables a robust reduction and quantification of the uncertainties of excess phases and bending angles in the lower troposphere.
关键词： wave-optics uncertainty propagation,bending angle retrievals,refractivity fluctuation statistics,GNSS radio occultation,boundary layer bias model
更新于2025-09-10 09:29:36
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Strong Coupling in Microcavity Structures: Principle, Design, and Practical Application
摘要： When interaction between light and matter is in the strong coupling region, matter has a significant influence on the whole system, with potential to develop low-power active optical devices. Strong coupling can verify some basic problems of quantum physics, and it is an ideal system to study light–matter interaction, providing an intuitive and accurate demonstration of some pure quantum effects with small mass and easy optical control. Here, the most important advances in strong coupling in recent years are described. Of late, an extensive series of experimental and theoretical findings, and remarkable achievements have been made in this field. Strong coupling between cavities and some new materials such as semiconductors, two-dimensional (2D) material, and quantum dots (QDs) are the focus of research in this field. Another field that has made outstanding progress is the application of this optical phenomenon, including resonance-enhanced Raman and infrared spectra, nanolasers, and cavity-enhanced sensing. Furthermore, the potential in this field arises for future quantum information and quantum optical devices. It is now developing at a very fast rate and can be predicted to have broad prospects for development in the future. Some prospects in terms of design and application are included.
关键词： strong coupling,vacuum Rabi splitting,optical devices,quantum optics
更新于2025-09-10 09:29:36
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Resource-efficient fibre-integrated temporal multiplexing of heralded single photons
摘要： We present a multiplexed single photon source that re-synchronises heralded single photons generated by four-wave mixing in photonic crystal fibre using a fibre delay loop controlled by a single switch. By combining the probabilities of generating heralded single photons on four consecutive pump pulses we obtain an enhancement of the per-bin single-photon delivery probability. Our source demonstrates a way in which single-photon source multiplexing may be carried out with minimised resource overhead while retaining the benefits of a robust and alignment-free platform.
关键词： nonlinear optics,quantum optics,optical fibres
更新于2025-09-09 09:28:46
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Guiding of light with pinholes
摘要： A new type of light waveguide using linearly aligned pinholes is presented. Results of basic experiments are compared with theoretical estimates calculated using continuous model. This model predicts that the loss per unit length of the light inside this waveguide is proportional to the square root of the spacing between the pinholes. Since this waveguide utilizes no transparent material, it can be used to guide electromagnetic waves of wide wavelength ranges as well as other waves such as matter waves.
关键词： Waveguide,atom optics,diffraction optics
更新于2025-09-09 09:28:46
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Analytical Analysis of Residual Chromatic Dispersion and Self-Phase Modulation Optimal Compensation in the Fractional Domain
摘要： We present an analytical expression of residual chromatic dispersion and self-phase modulation optimal compensation with a chirped Gaussian pulse in the fractional domain. The accuracy of the expression is con?rmed by the simulation platform, which is based on the split-step Fourier method. Moreover, the simulation of a 28-GBd RZ-DQPSK optical ?ber communication system is carried out to verify the correctness when the transmission distance is less than 800 km in a standard single-mode ?ber and non-zero dispersion-shifted ?ber.
关键词： Metrology,?ber optics,fractional Fourier transform,?ber nonlinear optics
更新于2025-09-09 09:28:46
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Impact of higher-order aberrations on depth-of-field
摘要： It is well known that depth-of-focus (DOF) is influenced by optical factors (such as pupil size and monochromatic aberrations). However, neural factors such as blur sensitivity and defocus adaptation may play an important role on the extent of DOF. A series of experiments were conducted to study if optical or neural factors are most pertinent in explaining the variability of DOF across subjects. An adaptive optics system with a black and white target, a 3.8-mm artificial pupil, and a subjective criterion (based on objectionable blur) were used to measure depth of field ([DOFi]; DOF computed in the object space) in 11 participants, after at least 6 min of adaptation. This was done under three conditions: (a) with their own higher order aberrations (HOA); (b) after correction of their monochromatic HOA; and (c) after altering the HOA pattern for some participants to reflect the HOA pattern measured for a different participant. Natural DOFi and DOFi after HOA correction were positively correlated (R2 ? 0.461), but a significant decrease in DOFi (21% on average) was found after HOA correction (p ? 0.042). Effect of HOA on the intersubject variability of DOFi was 3.9 times smaller than the effect of the image neural processing. This study shows that DOFi depends on both optical and neural factors, but the latter seems to play a more important role than the former.
关键词： depth of focus,visual optics,wavefront aberrations,depth of field,physiological optics
更新于2025-09-09 09:28:46
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High-Speed Reconfigurable Free-Space Optical Interconnects with Carrierless-Amplitude-Phase Modulation and Space-Time-Block Code
摘要： High-speed interconnects are highly demanded in data centers and high-performance computing, and the use of optical interconnects to replace electrical interconnects has been proposed and widely studied. For medium-range board-to-board communications, free-space based optical interconnects provide the additional advantage of reconfigurability and flexibility, compared with traditional waveguide or fiber based counterparts. However, the bit rate and interconnection range in free-space optical interconnects are typically limited. In this paper, we propose a carrierless-amplitude-phase (CAP) modulated and space-time coded free-space optical interconnect scheme to overcome these limitations. Up to 80 Gb/s (2×40 Gb/s) interconnection with reconfigurability and flexibility is experimentally demonstrated for a maximum error-free distance exceeding 50 cm, showing about 65% improvement over previous demonstrations. The receiver sensitivity of the space-time coded system is measured as well, and results show that the space-time-block code (STBC) is capable of improving the receiver sensitivity and suppressing the inter-channel crosstalk. The impact of air turbulence, which exists in typical interconnect environments, is also experimentally investigated and results show that its impact on the proposed scheme is negligible. The proposed reconfigurable free-space optical interconnects with CAP and STBC can be further scaled up to provide higher speed and further extended interconnection range.
关键词： free-space optics,carrierless-amplitude-phase modulation,air turbulence,space-time-block-code,Optical interconnects
更新于2025-09-09 09:28:46
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Nonlinear Quasi-Phase Matching with metasurfaces
摘要： Quasi-Phase Matching is an optical process needed to build up nonlinear signal from strong pump intensity and is generally obtained through periodical inversion of coherence domains of the crystal. We show that this effect can be arti?cially monitored through inserting metasurfaces along the optical path of the light in a waveguide. Sub-wavelength gratings of holes are etched in Gallium Nitride to locally change medium dispersion, allowing continuous increase of the second harmonic signal. This approach can be used to address any phase delay difference between pump and signal at will, not only π, opening up new perspectives for arbitrary phase matching conditions. It can also be implemented in highly nonlinear systems, in which it is generally hard to address phase-matching conditions, for instance waveguides with buried intersubband quantum wells or other materials such GaAs.
关键词： second harmonic generation,metasurfaces,Quasi-Phase Matching,Gallium Nitride,nonlinear optics
更新于2025-09-09 09:28:46
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Vortex instability in turbulent free-space propagation
摘要： The spatial structuring of optical fields is integral within many next generation optical metrology and communication techniques. A verifiable physical model of the propagation of these optical fields in a turbulent environment is important for developing effective mitigation techniques for the modal degradation that occurs in a free-space link. We present a method to simulate this modal degradation that agrees with recently reported experimental findings. A 1.5 km free-space link is emulated by decomposing the optical turbulence that accumulates over a long distance link, into many, weakly perturbing steps of 10 m. This simulation shows that the high-order vortex at the centre of the helical phase profiles in modes that carry orbital angular momentum of ? are unstable and fracture into many vortices when they propagate over the link. This splitting presents issues for the application of turbulence mitigation techniques. The usefulness of pre-correction, post-correction, and complex field conjugation techniques are discussed.
关键词： optical propagation,orbital angular momentum,adaptive optics,optical vortices,atmospheric turbulence
更新于2025-09-09 09:28:46