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[IEEE 2018 International Conference on Advances in Computing, Communications and Informatics (ICACCI) - Bangalore (2018.9.19-2018.9.22)] 2018 International Conference on Advances in Computing, Communications and Informatics (ICACCI) - Cumulative Amplifier and Doppler Effect on PSK modulated signals in Inter-Satellite Communication
摘要： The paper brings out the cumulative effect of Doppler frequencies on Saleh type non-linearity for a PSK (Phase Shift Keying) modulated signal in Intersatellite communication link. The distortion introduced is measured by taking Error Vector Magnitude (EVM) as metric of evaluation. A PSK modulated signal is considered for study and the equation for the EVM is derived for the PSK signal affected with Doppler and Saleh type non-linearity. The Intersatellite links to be employed for the proposed constellation get affected with Doppler. The Doppler frequency changes with the frequency of operating signal. In this paper a time invariant Doppler is considered and its effect on the PSK signal is brought out. The PSK type considered is QPSK and the effect of amplifier linearity is first derived and then the effect of Doppler is applied onto it. The EVM expression derived is the power reference the EVM expression results are presented for variation of EVM with doppler frequency. From the results it can be observed that a) The EVM varies non-periodically with the Doppler frequency. b) The EVM value changes for different Saleh Parameters and changes with the Doppler frequency. The EVM values are found to worse for Saleh parameters that have higher values of slope in the amplifier characteristics.
关键词： Saleh model non-linearity,Cube Satellite-microsatellite constellation,Doppler and Phase error,Intersatellite Links
更新于2025-09-19 17:15:36
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Non-paraxial theory of self-focusing/defocusing of Hermite cosh Gaussian laser beam in rippled density plasmas
摘要： Present research work focuses on study of self-focusing and self-trapping of Hermite cosh Gaussian (HchG) laser beams in rippled density plasma by considering relativistic non-linearity. The coupled non-linear differential equations for the beam width parameters (for modes m = 0, 1, and 2) were derived by employing higher-order correction in comparison to paraxial ray theory by expanding dielectric function and eikonal up to r4 terms. It is observed that the inclusion of higher-order terms significantly influence the off-axial properties for m ≥ 1 mode indices. Furthermore, the effect of parameters including beam intensity, ripple factor, depth of density modulation, and decentred parameter on self-focusing and self-trapping is analysed and discussed both analytically and numerically.
关键词： self-focusing,Hermite cosh Gaussian beam,self-trapping,relativistic non-linearity
更新于2025-09-19 17:13:59
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Distributed Kerr Non-linearity in a Coherent All-Optical Fiber-Ring Reservoir Computer
摘要： We investigate, both numerically and experimentally, the usefulness of a distributed non-linearity in a passive coherent photonic reservoir computer. This computing system is based on a passive coherent optical fiber-ring cavity in which part of the non-linearities are realized by the Kerr non-linearity. Linear coherent reservoirs can solve difficult tasks but are aided by non-linear components in their input and/or output layer. Here, we compare the impact of non-linear transformations of information in the reservoirs input layer, its bulk—the fiber-ring cavity—and its readout layer. For the injection of data into the reservoir, we compare a linear input mapping to the non-linear transfer function of a Mach Zehnder modulator. For the reservoir bulk, we quantify the impact of the optical Kerr effect. For the readout layer we compare a linear output to a quadratic output implemented by a photodiode. We find that optical non-linearities in the reservoir itself, such as the optical Kerr non-linearity studied in the present work, enhance the task solving capability of the reservoir. This suggests that such non-linearities will play a key role in future coherent all-optical reservoir computers.
关键词： Kerr,fiber-ring,distributed non-linearity,photonic,coherent,reservoir computing,passive
更新于2025-09-16 10:30:52
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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) - Electro-Optic Frequency Comb Generation in Lithium Niobate Whispering Gallery Mode Resonators
摘要： Optical frequency combs (OFCs) are light sources whose spectra consists of equally spaced frequency lines in the optical domain [1]. They have great potential for improving high-capacity data transfer, all-optical atomic clocks, spectroscopy, and high-precision measurements [2]. In contrast to the traditional third-order nonlinearity based OFC generation methods, we present a new approach which is based on second-order non-linear effects in a whispering gallery mode (WGM) resonator made of lithium niobate (LN) [3,4]. Our system is composed of a resonant hybrid structure comprising an optical LN disk resonator and a microwave copper cavity. The hybrid structure enables highly efficient nonlinear mixing of photons. In this scheme, two continuous waves, one in the optical domain ((cid:2033) = 193 THz) and another in the microwave region (Ω = 8.9 GHz) couple within a LN WGM resonator [5]. The second-order non-linearity of LN leads to frequency comb generation via cascaded symmetric sum and difference frequency generation [6]. In our experiment, the optical pump power is coupled into the WGM by using a standard prism coupling method that is based on frustrated total internal reflection (Fig. 1 (a)). The microwave power is coupled using a coaxial probe coupled attached to the 3-D copper cavity specifically designed to have the microwave cavity resonance to be equal to the optical free spectral range of the LN resonator, required for efficient phase matching. In addition, the cavity design also provides a very good spatial overlap between the microwave and optical modes by confining the microwave field to the rim of the LN disk. In our proof-of-concept experimental demonstration we observe a 1.6 THz long frequency comb centred around 193.5 THz more than180 comb lines by using only 20 dBm of microwave power. Compared to previously reported OFCs generation schemes, this method has two major advantages: inherent phase stability, and better power efficiency. The power efficiency when measured in terms of pi-voltage of the modulator is 25 times better than a commercial Thorlabs modulator.
关键词： second-order non-linearity,whispering gallery mode resonators,electro-optic frequency comb generation,Optical frequency combs,lithium niobate
更新于2025-09-12 10:27:22
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THz generation in laser-induced breakdown in carbon dioxide at different levels of gas pressure
摘要： The present paper studies the generation of terahertz (THz) radiation in carbon dioxide (CO2) at different levels of gas pressure. It was demonstrated that under low gas pressure optical-terahertz conversion (OTC) can be adequately described by a simplified photocurrent model. However, with the increase of gas pressure the contribution of intra-atomic non-linearities as a source of terahertz response irradiated by a two-color laser field is growing. Moreover, at high levels of gas pressure the interference and dispersive effects should be taken into consideration as well. The proposed model allows for the optimization of experimental conditions aimed at flexible control of intensity and spectral properties of THz radiation.
关键词： terahertz,photocurrent model,intra-atomic non-linearity,laser-induced plasma
更新于2025-09-11 14:15:04
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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) - Non-linearity Enhances Versatility of Non-Foster Metamaterials and Metasurfaces
摘要： Classical applications of non-Foster elements such as broadband active metamaterials/metasurfaces and broadband matching of small antennas presume their linearity. Here, we show that two well-known types of negative impedance converters - the voltage-conversion type and the current-conversion type, show fundamentally different behavior in non-liner regime. It is followed by different power-dependent properties of generated positive/negative susceptance/reactance. This effect may be used in future self-oscillating and self-mixing metasurfaces as well as in power-tunable metamaterials/metasurfaces.
关键词： negative impedance converters,non-linearity,metamaterials,non-Foster elements,metasurfaces
更新于2025-09-10 09:29:36
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Dynamics of Kerr-like medium with two-mode intensity-dependent cavity fields
摘要： The dynamics of an effective two-level atom coupled to two-mode intensity-dependent quantized cavity fields via a ladder process in the presence of a Kerr medium has been investigated. Eigenfunctions and eigenvalues of the Hamiltonian of the interacting system have been obtained using a unitary transformation method. The cavity field statistics and non-classical properties are investigated numerically through second-order correlation functions. The effect of detuning and the Kerr medium on the non-classical features of the atom-field state has been analyzed. We find that the presence of Kerr non-linearity enhances the non-classical correlation between the correlated beams at short time intervals and increases antibunching at short time intervals.
关键词： intensity-dependent coupling,antibunching,photon statistics,Kerr non-linearity,two-mode ladder model,Cauchy–Schwartz inequality,second-order correlation functions
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE Photonics Conference (IPC) - Reston, VA, USA (2018.9.30-2018.10.4)] 2018 IEEE Photonics Conference (IPC) - 10-Gb/s Transmission Over 10-m SI-POF with M-PAM and Multilayer Perceptron Equalizer
摘要： We demonstrate the gigabit-per-second transmission over a step-index plastic optical fiber (SI-POF) of 10-m length with a pulse-amplitude modulation (PAM). A multilayer perceptron-based equalizer is used to mitigate an intersymbol interference and non-linearity in the system. Using this equalizer with 32-PAM, a data rate of 10 Gb/s is achieved over the 10-m SI-POF at a bit error rate of 10?2, which is below the 20% forward error correction limit.
关键词： multilayer perceptron (MLP),Polymer optical fiber (POF),pulse amplitude modulation (PAM),decision feedback equalizer,non-linearity
更新于2025-09-04 15:30:14