- 标题
- 摘要
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- 实验方案
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Effect of quintic nonlinearity on self-phase modulation and modulation instability in multiple coupled quantum wells under electromagnetically induced transparency
摘要： The self-phase modulation and modulation instability of an optical probe electromagnetic field in multiple quantum well systems under electromagnetically induced transparency has been investigated. The probe field experiences large Kerr and quintic nonlinearities that can be controlled by two controlling laser beams. The probe beam experiences self-phase modulation which is suppressed by the quintic nonlinearity. The probe field is modulationally unstable due to the existence of large nonlinearities. The bandwidth of unstable frequencies and growth of the instability could be controlled by the probe beam power, the Rabi frequency and detunings of two control fields. The presence of the higher order nonlinearity and dispersion significantly reduce the instability growth and bandwidth of unstable frequency.
关键词： Self-phase modulation,Coupled quantum well,Modulation instability,electromagnetically induced transparency
更新于2025-09-23 15:21:01
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A perturbative approach to self-phase modulation and self-steepening of short laser pulses propagating in nonlinear media
摘要： The solution of the wave equation in the envelope approximation with temporal corrections for a laser pulse propagating in a medium where the Kerr effect, field ionization, and associated absorption take place, is obtained through a first order perturbative approach. Dispersion is, however, neglected to decouple the equations for the amplitude and the phase. The closed-form expressions so obtained clarify the influence of the various terms of the equation on the laser amplitude and on the frequency generation as a function of the retarded time. Furthermore, they allow extracting scaling parameters which size the nonlinear effects. The results are illustrated quantitatively in the case of a femtosecond pulse focused in the air with typical parameters.
关键词： perturbative approach,self-phase modulation,self-steepening,short laser pulse propagation
更新于2025-09-23 15:21:01
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Transmissive flexoelectro-optic liquid crystal optical phase modulator with 2 <b>??</b> modulation
摘要： In this paper, we demonstrate analog phase modulation in a transmissive configuration using the flexoelectro-optic effect in short-pitch chiral nematic liquid crystal (LC) devices. Two different modes are considered, both of which are shown to generate full 2π phase modulation at 1 kHz switching frequency. The first configuration that is considered consists of a half-wave plate that is placed between two flexoelectro-optic LC devices that are subjected to electric fields that are applied in phase. Second, we demonstrate that a similar phase modulation response can be observed by removing the half-wave plate and subjecting the two flexoelectro-optic LC devices to electric fields whereby the polarities are out of phase. Both configurations demonstrated herein are promising for the development of next-generation LC spatial light modulators, particularly when reflective geometries are challenging or impractical.
关键词： spatial light modulators,flexoelectro-optic effect,liquid crystal,phase modulation,transmissive configuration
更新于2025-09-23 15:21:01
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Electrical Phase Control Based on Graphene Surface Plasmon Polaritons in Mid-infrared
摘要： Phase modulation of light is the core of many optoelectronic applications, such as electro-optic switch, sensors and modulators. Graphene Surface plasmon polaritons (SPPs) exhibit unique properties in phase modulation including dynamic tunability, a small driving voltage and small device size. In this paper, the novel phase modulation capability of graphene SPPs in mid-infrared are confirmed through theory and simulation. The results show that graphene SPPs can realize continuous tuning of the phase shift at multiple wavelengths in mid-infrared, covering the phase range from 0° to 360°. Based on these results, a sandwich waveguide structure of dielectric–graphene–dielectric with a device length of 800 nm is proposed, which shows up to 381° phase modulation range at an operating wavelength of 6.55 μm, given a 1 V driving voltage. In addition, the structure size is much shorter than the wavelength in mid-infrared and can realize sub-wavelength operation. This work paves the way to develop graphene-based tunable devices for mid-infrared wave-front control.
关键词： Mid-infrared,phase modulation,graphene surface plasmon polaritons
更新于2025-09-23 15:19:57
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Radiation of a Resonant Medium Excited by a Periodically Phase-Modulated Laser in the Regime of Strong Coupling between the Field and the Matter
摘要： The radiation of a two-level resonant medium that is placed into a cavity and is excited by a periodically phase modulated laser pulse is studied theoretically. The radiation is analyzed based on the analytical and numerical solutions of the system of Maxwell–Bloch equations under conditions of a strong coupling between the field and the matter. Under these conditions, this system is similar to a polariton laser. The excitation efficiency of a polariton laser by a phase-modulated radiation pulse is shown to be high compared to a pulse without phase modulation of the carrier frequency. It is shown that the main reason for the efficient excitation of polariton modes in the medium is the appearance of difference combination parametric resonance. The obtained results open up new possibilities for the excitation of radiation of polariton lasers by low-power frequency-modulated pump laser radiation.
关键词： phase modulation,Rabi vacuum splitting,strong coupling,polariton laser
更新于2025-09-23 15:19:57
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Demonstration of a Hybrid FSO/VLC Link for the Last Mile and Last Meter Networks
摘要： In this paper, a hybrid free-space optical and visible light communication (FSO/VLC) system was experimentally demonstrated as a solution to overcome the last mile and last meter access networks bandwidth bottleneck. We evaluate the system performance of a multiband carrier-less amplitude and phase (m-CAP) modulation scheme for a range of FSO/VLC link lengths and m-CAP parameters (i.e., the roll-off factor of the ?lters and a number of subcarriers) in terms of the data rate Rb (i.e., spectral ef?ciency). We show that for the con?guration with a 1 m VLC link the 10-CAP offers more than a 40 % improvement in the measured Rb compared to 2-CAP for the same bit error rate target. The Rb penalty due to the extension of a VLC link span from 1 m to 3 m reaches to 12.6 Mb/s for the 10-CAP scheme (i.e., ～39 % degradation in Rb). To fully cover all aspects of the hybrid FSO/VLC system, we also investigate the atmospheric turbulence effect on the 500 m FSO link n of 2.4×10?15 m?2/3 where Rb is decreased by 30 % for the refractive index structure parameter C2 compared to a clear channel condition.
关键词： multiband carrier-less amplitude and phase modulation,Visible light communication,free space optics
更新于2025-09-23 15:19:57
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Spatial Carrierless Amplitude and Phase Modulation Technique for Visible Light Communication Systems
摘要： Spatial carrierless amplitude and phase modulation (S-CAP) technique is developed in this paper as a physical layer solution to improve the spectral efficiency of the conventional CAP scheme while preserving its low-complexity transceiver design. The S-CAP technique is proposed and investigated for systems employing the visible light communication technology. An analytical expression for the joint detection of the spatial and signal bits for the user equipment experiencing line-of-sight propagation (LOS) is derived and validated via simulation. The effects of the multipath propagation and user mobility on the bit-error-rate (BER) performance of the proposed S-CAP are also investigated. It is found that the BER performance of the S-CAP in LOS is dictated by the minimum of the channel gains hmin, the signal constellation points, and the channel gain dissimilarity, Δ|h|. The power factor imbalance (PFI) and multiple photodetectors (PDs) are then introduced to improve the performance and mitigate the channel impairments. The use of the PFI and PDs in LOS results in the signal-to-noise gain of 33.5 and 43 dB, respectively. The proposed scheme is thus a novel implementation of the CAP in a multiple-input–multiple-output system and demonstrates its potential as a suitable physical layer solution for the VLC technology.
关键词： multiple-input–multiple-output (MIMO),visible light communication (VLC),Carrierless amplitude and phase modulation (CAP),multipath propagation,spatial modulation (SM)
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 30th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) - Istanbul, Turkey (2019.9.8-2019.9.11)] 2019 IEEE 30th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) - Hybrid Super-Nyquist CAP Modulation based VLC with Low Bandwidth Polymer LEDs
摘要： Visible light communication systems often suffer from high frequency attenuation when transmitting out-of-band. This effect has been ameliorated by multi-band modulations such as multi-band carrier-less amplitude and phase (m-CAP), which minimises the effect of decreased high frequency magnitude and maximises signal-to-noise ratio-per-sub-band. On the other hand, in the pass-band region, super-Nyquist CAP (SCAP) can offer throughput improvements with no additional complexity at the receiver, at the cost of bit error rate. We propose, for the first time, a new hybrid SCAP modulation format that takes advantageous of both SCAP (i.e. overlapped sub-bands within the modulation bandwidth) and conventional m-CAP (orthogonally spaced bands outside the modulation bandwidth) while maintaining isolation between noise sources. We show higher baud rates within the passband region whilst supporting out-of-band transmission at lower error vector magnitudes.
关键词： modulation,digital signal processing,Carrier-less amplitude and phase modulation,visible light communications
更新于2025-09-19 17:13:59
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Infrared subwavelength focusing metasurfaces for harvesting heat from the Eartha??s back radiation
摘要： In this paper, we introduce two different metasurfaces that can achieve subwavelength focusing of the electromagnetic radiation in the infrared range with transmission ef?ciencies reaching 46% and 74.33% in silicon and thus they can be integrated in heat harvesting applications. We made our designs at the wavelength of 10 μm which is the peak of the back radiation of the Earth. In designing our metasurfaces in the infrared range, we used the phase modulation techniques that proved to be useful in the visible domain. The best focusing resolution achieved in our metasurfaces is 0.26λ (super-focusing). In addition to heat harvesting, the two proposed metasurfaces can be useful in other compact applications that require manipulating the mid-infrared radiation on a very small scale. We used copper and silicon in our metasurfaces which are speci?cally suitable for the mid-infrared range besides being CMOS compatible. In this paper, we also explained how heat can be harvested from the introduced metasurfaces using the Seebeck effect.
关键词： plasmonics,subwavelength focusing,planar lens,phase modulation,heat harvesting,metasurface,mid-infrared focusing
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Nonlinear compression of ultra-high-power laser pulses
摘要： Nowadays the peak power of PW lasers is limited by the damage threshold of optical compressor diffraction gratings. A promising way to overcome the difficulty and increase peak power is to use an additional pulse shortening after optical compressor without significant energy loses. The discussed method is called CafCA – Compression after Compressor Approach. CafCA possesses three undisputed merits: simplicity and low cost, negligible pulse energy loss, and applicability to any high-power lasers without changing their optical schemes. The key idea of the approach is to broaden spectrum of powerful laser pulses exactly after grating compressor and correct spectral phase with help of reflected dispersion devices (chirped mirrors in particular). The idea has been known since the end of 1960s but its application to lasers with a peak power higher 1 TW has been restricted by a number of physical reasons. The reasons and ways of its overcoming are discussed in the paper. We analyze the recent experimental results that demonstrate the CafCA efficiency in the range up to 200 TW.
关键词： temporal compression,self-phase modulation,PW-level femtosecond laser pulses
更新于2025-09-19 17:13:59