- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Effects of a chiral atomic medium on the manipulation of light birefringence and lateral Goos–H?nchen shifts via Kerr nonlinearity and local field effects
摘要： We present a new scheme to report on the effects of a five-level chiral atomic medium on the lateral Goos–H?nchen (GH) shift in Gaussian probe beams via Kerr nonlinearity (KNL) and local field effects. The physical realization of birefringence in absorption, dispersion, reflection and transmission beams is investigated, with special emphasis on the manipulation of absolute and fractional change in lateral GH shifts in birefringence transmission and reflection beams, via local fields and Kerr nonlinearity. We have employed a semiclassical atomic density-matrix formalism so as to obtain the expression for electric and magnetic susceptibilities of the chiral medium and the corresponding chirality coefficients in conjunction with Kerr and local fields, both separately and in combination. Stationary-phase theory is used to compute GH shift from the calculated birefringent reflection and transmission coefficients of probe beams. A negative and positive GH shift is observed in reflection and transmission beams, respectively, subjected to local field and Kerr effect. In contrast, a positive GH shift is observed in both reflection and transmission beams in the presence of both local field and Kerr effects. The local and Kerr fields also alter the divergence angle between left and right circularly polarized birefringence beams. GH shift depends on incident angle and probe detuning. The anisotropy of medium is lessened by switching ON the Kerr field in the medium. We observed a positive fractional change of ±30% in the GH shift in the birefringence reflection beam in the presence of a local field without KNL, while a 20% fractional GH shift was observed in the presence of both local field and KNL effects. Our results suggest promising applications in nonlinear optical, plasmonic and biophotonic devices for the manipulation of light propagation and optical signal processing.
关键词： stationary-phase theory,Kerr nonlinearity,birefringence chiral medium,Goos–H?nchen shift,density-matrix formalism,Doppler broadening medium
更新于2025-09-23 15:19:57
-
Nonlinear Performance of Few-Mode Fiber Links with Intermediate Coupling
摘要： This paper reviews and extends the study of nonlinear performance of few-mode fiber links operating in all different linear coupling regimes for different mode delay maps. Nonlinear performance was estimated using the four-wave-mixing theory and the split-step Fourier method including semi-analytical solutions for linear mode coupling of arbitrary strength. The optimum link configurations minimizing the nonlinear penalty at practical levels of training sequence length are presented, including: the required coupling strength to give nonlinear distortion below that of the single-mode propagation without mode coupling, and the impact of mode delay maps. Finally, different approximate solution methods of the multimode nonlinear Schr?dinger equation are compared, highlighting the accuracy of a stochastic solution method including distributed linear mode coupling.
关键词： Mode-division multiplexing,few-mode fiber,linear mode coupling,fiber nonlinearity
更新于2025-09-19 17:15:36
-
[IEEE 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - Shenzhen, China (2018.7.13-2018.7.15)] 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - A Nonlinear FDA Optimal Frequency Increment Selection Method
摘要： According to the idea of cognitive radar, the frequency increment in frequency diverse array (FDA) needs to be adaptively adjusted to the changed environments so that the FDA’s anti-jamming performance always is optimal. The nonlinear frequency increment can eliminate the traditional FDA beam’s periodicity in range and form a single peak beam, which is helpful to the detection of the target. In view of this, this paper presents a nonlinear FDA optimal frequency increment selection method. It derives the intrinsic relationship between the output SINR and the frequency increment. Within a coherent processing interval (CPI), the frequency increment can be adaptively selected corresponding to the minimum modulus of the array weight vector and then it is fed back to the transmitter and applied to the next CPI. Both the theories and simulations show that FDA has a better anti-interference ability after taking optimal frequency increment by this method.
关键词： frequency diverse array,adaptive frequency,anti-interference,nonlinearity,optimal increment
更新于2025-09-19 17:15:36
-
The Influence of Quantum Confinement on Third-Order Nonlinearities in Porous Silicon Thin Films
摘要： We present an experimental investigation into the third-order nonlinearity of conventional crystalline (c-Si) and porous (p-Si) silicon with Z-scan technique at 800-nm and 2.4-μm wavelengths. The Gaussian decomposition method is applied to extract the nonlinear refractive index, n2, and the two-photon absorption (TPA) coefficient, β, from the experimental results. The nonlinear refractive index obtained for c-Si is 7 ± 2 × 10?6 cm2/GW and for p-Si is ?9 ± 3 × 10?5 cm2/GW. The TPA coefficient was found to be 2.9 ± 0.9 cm/GW and 1.0 ± 0.3 cm/GW for c-Si and p-Si, respectively. We show an enhancement of the nonlinear refraction and a suppression of TPA in p-Si in comparison to c-Si, and the enhancement gets stronger as the wavelength increases.
关键词： Z-scan,third-order nonlinearity,TPA,porous silicon,self-focusing
更新于2025-09-19 17:15:36
-
Nonlinearity mitigation in multi-IFoF-based mobile fronthaul transmission using spectral power shaping
摘要： We propose a spectral power shaping technique for use in intermediate frequency (IF) over fiber systems. The technique redistributes the power of nonlinear components by adjusting the spectral power of the signal. Experiments performed using 10 km distance transmission system show that the proposed technique effectively controls the power of the nonlinear components in a broadband system. The feasibility of the proposed technique was experimentally verified in terms of the error vector magnitude (EVM) and degree of channel linearity.
关键词： IFoF system,Intermodulation distortion,Nonlinearity mitigation,Spectral power shaping
更新于2025-09-19 17:15:36
-
Enhanced second harmonic generation of Hermitea??Gaussian laser beam in plasma having density transition
摘要： Under the combined effect of relativistic and ponderomotive nonlinearity, resonant second harmonic generation of an intense Hermite–Gaussian (H–Gaussian) laser beam in a plasma having upward density ramp profile has been theoretically investigated. Under WKB approximation and with the use of the moment theory approach the coupled differential equations are derived which govern the spot size of the H–Gaussian laser beam. The ponderomotive force creates the density gradient in the background plasma electrons which is responsible for the excitation of the electron plasma wave. The large-amplitude electron plasma wave interacts with the fundamental beam which produces coherent radiations with double the frequency of the incident beam. In addition, the Gouy phase shift is observed for the H–Gaussian laser beam in plasma under the effect of density transition. The analysis shows the vital role of the different modes of the H–Gaussian laser beam and density ramp on the efficiency of generated harmonics and self-phase shift of laser beams in plasma.
关键词： ponderomotive,density ramp,second harmonic generation,relativistic nonlinearity,Hermite–Gaussian laser beam
更新于2025-09-19 17:13:59
-
Introducing Enumerative Sphere Shaping for Optical Communication Systems with Short Blocklengths
摘要： Probabilistic shaping based on constant composition distribution matching (CCDM) has received considerable attention as a way to increase the capacity of fiber optical communication systems. CCDM suffers from significant rate loss at short blocklengths and requires long blocklengths to achieve high shaping gain, which makes its implementation very challenging. In this paper, we propose to use enumerative sphere shaping (ESS) and investigate its performance for the nonlinear fiber optical channel. ESS has lower rate loss than CCDM at the same shaping rate, which makes it a suitable candidate to be implemented in real-time high-speed optical systems. In this paper, we first show that finite blocklength ESS and CCDM exhibit higher effective signal-to-noise ratio than their infinite blocklength counterparts. These results show that for the nonlinear fiber optical channel, large blocklengths should be avoided. We then show that for a 400 Gb/s dual-polarization 64-QAM WDM transmission system, ESS with short blocklengths outperforms both uniform signaling and CCDM. Gains in terms of both bit-metric decoding rate and bit-error rate are presented. ESS with a blocklength of 200 is shown to provide an extension reach of about 200 km in comparison with CCDM with the same blocklength. The obtained reach increase of ESS with a blocklength of 200 over uniform signaling is approximately 450 km (approximately 19%).
关键词： optical communication systems,enumerative sphere shaping,probabilistic shaping,fiber nonlinearity,Constant composition distribution matching
更新于2025-09-19 17:13:59
-
Nondestructive Evaluation of Thermal Aging in Al6061 Alloy by Measuring Acoustic Nonlinearity of Laser-Generated Surface Acoustic Waves
摘要： The structures in high-temperature environments are prone to undergo hardening and embrittlement as a result of thermal aging; this can cause variations in their mechanical properties. Because these changes occur at the microstructural level, it is difficult to evaluate them through linear ultrasonic techniques. In this work, a surface acoustic wave (SAW) was used to measure and compare the acoustic nonlinearity and mechanical properties of Al6061 alloys heat-treated at 220°C for different durations (0 min, 20 min, 40 min, 1 h, 2 h, 10 h, 100 h, 1000 h). The SAW was generated by a pulsed laser and then received by an interferometer. Moreover, the yield strength, ultimate strength, and elongation to failure were measured by tensile tests. The results demonstrate that the critical variations in the mechanical properties can be detected by monitoring the variation features in the acoustic nonlinearity. Transmission electron microscopy images were captured to observe the microstructural changes, which shows that the acoustic nonlinearity varied according to the change in the precipitation phase. This supports the acoustic nonlinearity measurement using the laser-generated SAW being an effective technique for the fully noncontact nondestructive evaluation of material degradations as well as changes in mechanical properties.
关键词： surface acoustic wave,material degradation,laser,heat treatment,mechanical property,thermal aging,nonlinear parameter,precipitation,acoustic nonlinearity
更新于2025-09-19 17:13:59
-
[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) - Direct Quantum Error Detection in Spatially Multiplexed Transmission
摘要： In this paper, we investigate the properties of transmission links amplified by phase-sensitive amplifiers (PSAs). Using an analytic description, we explain the principles enabling improved sensitivity compared to conventional links amplified by phase-insensitive amplifiers (PIAs) and mitigation of nonlinear transmission distortions. We demonstrate these features using numerical simulations, and in particular, we show the possibility of efficiently mitigating both self-phase modulation (SPM)-induced distortions and nonlinear phase noise (NLPN) if the link dispersion map is optimized. The properties of the noise on signal and idler are important and to enable NLPN mitigation, the noise must be correlated at the link input. We investigate the role of the dispersion map in detail and show that in a link with standard single mode fiber (SSMF) the optimum dispersion map for efficient nonlinearity mitigation corresponds to precompensation of an amount equal to the effective loss length. Furthermore, we experimentally demonstrate both improved sensitivity and mitigation of nonlinearities in a 105 km PSA-amplified link transmitting 10 GBd 16-ary quadrature amplitude modulation (16QAM) data. We measure a combined effect allowing for more than 12 dB larger span loss in a PSA-amplified link compared to a conventional PIA-amplified link to reach the same bit error ratio (BER) of 1 × 10?3.
关键词： phase-sensitive amplifiers (PSAs),Fiber nonlinearity mitigation,optical amplifiers,optical fiber communication,phase-conjugated twin waves,fiber optical parametric amplifiers (FOPAs)
更新于2025-09-19 17:13:59
-
Optical solitons with nonlocal-parabolic combo nonlinearity by Lie symmetry analysis coupled with modified G′/G-expansion
摘要： This paper obtains optical soliton solutions with parabolic law nonlinearity coupled in nonlocal nonlinear medium. Lie symmetry analysis coupled with modified G′/G-expansion scheme retrieves these solitons.
关键词： Parabolic law,Weakly nonlocal nonlinearity,Modified G′/G-expansion,Lie symmetry,Solitons
更新于2025-09-19 17:13:59