- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Relativistic Self Focusing and Frequency Shift of super-Gaussian Laser Beam in Plasma
摘要： Relativistic self focusing and frequency shift of laser beam having super-Gaussian profile in space and Gaussian profile in time is studied in a plasma. The relativistic mass nonlinearity is found to cause time dependent self focusing of the laser pulse and the saturation effect of nonlinearity avoids point focusing of the beam. For ultrashort laser pulse, the front of the pulse undergoes frequency down shift while that of the tail undergoes up shift. Frequency shift increases and self focusing becomes stronger for higher intensity of the laser. The self focusing is also stronger for the laser beam carrying larger wavelength.
关键词： Beam width parameter,Self focusing,Frequency shift,super-Gaussian laser,Moment Theory,Relativistic nonlinearity
更新于2025-09-23 15:21:01
-
Temperature dependent Raman frequency model for monoatomic crystals
摘要： In the present study, a theoretical model for the temperature dependence of Raman frequency shift without any adjustable parameters is established. The model builds a relationship between the temperature dependent Raman frequency and the Raman frequency at a reference temperature. To verify the present model, the temperature dependent Raman frequency shifts of Ge, α-Sn, and Si are predicted, which are in excellent agreement with the available experimental results, Balkanski’s theory and Kolesov’s theory. Besides, the model indicates that the variations in special heat with temperature determine the temperature dependent Raman frequency. This work can provide a convenient method to predict the temperature dependent Raman frequency shift for monoatomic crystals.
关键词： Raman frequency shift,semiconductor,temperature dependent,modelling
更新于2025-09-23 15:21:01
-
Laser frequency shift up to 5 GHz with a high-efficiency 12-pass 350-MHz acousto-optic modulator
摘要： We demonstrate a novel laser frequency shift scheme using a 12-pass 350-MHz acousto-optic modulator (AOM). This AOM system shows better performance compared to ordinary acousto-optic modulation schemes. The frequency of the incident laser beam is shifted by 4.2 GHz with the total diffraction efficiency as high as 11%, and the maximum frequency shift is 5 GHz. Combining the ±1st order diffraction, laser signals with up to 10 GHz frequency difference can be obtained, which fulfill most frequency shift requirements of laser cooling and coherent manipulation experiments with alkali metal atoms.
关键词： frequency stability,diffraction efficiency,acousto-optic modulator,multi-pass AOM,laser frequency shift
更新于2025-09-23 15:19:57
-
[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou, China (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - Polarization-dependent High Quality Optical Frequency Comb Generator Based on Recirculating Frequency Shift
摘要： A polarization-dependent optical frequency comb (OFC) generation scheme based on recirculating frequency shift (RFS) is proposed and demonstrated. A dual-parallel Mach-Zehnder modulator (DPMZM) is employed to perform the carrier suppressed single sideband (CS-SSB) modulation and a polarization modulator (PolM) is adopted to generate a 5-line OFC. They are working in two orthogonal polarizations, respectively. The simulation results show that the proposed scheme can generate a 120-line OFC with flatness of 3.91 dB.
关键词： recirculating frequency shift (RFS),optical frequency comb (OFC),flatness,carrier suppressed single sideband modulation (CS-SSB)
更新于2025-09-19 17:15:36
-
[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou, China (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - Photonic generation of microwave frequency shift keying signals based on dual parallel Mach-Zehnder modulator structure
摘要： A novel scheme to generate microwave frequency shift keying (FSK) signals is proposed and verified by a simulation. The main devices are two single-drive Mach Zehnder modulators (MZM) and a commercial phase modulator (PM). They are parallelly settled to perform the FSK signal generation. In this simulation work, two MZMs are driven by the RF signals with a phase difference which is introduced by an electrical phase shifter (EPS). Simultaneously, the PM is driven by a binary coding signal. The simulation results show that when the two MZMs are biased at the maximum transmission point (MATP), a microwave FSK signal can be obtained with the frequency is two times as large as the RF frequency for bit '0' and four times as large as the RF frequency for bit '1', respectively. It should be noted that the system shows excellent adaption to the non-ideal extinction radio and the inherent inaccurate phase shift of the electrical phase shifter. Therefore, the generated microwave FSK signal can meet the requirement of high-frequency applications.
关键词： high-frequency applications,microwave signal generation,microwave photonics,frequency shift keying
更新于2025-09-19 17:15:36
-
Relativistic nonlinear frequency shift of laser pulse on reflection from critical layer in inhomogeneous plasma
摘要： An analytical formalism is developed for the nonlinear frequency shift of intense laser pulse, due to relativistic mass nonlinearity (in the sub-relativistic regime), on re?ection from the critical layer in an inhomogeneous plasma. As a higher and higher intensity front of the pulse approaches the critical layer, the re?ection layer moves forward to higher densities, due to the relativistic increase in the electron mass, causing a red shift in the re?ected wave frequency. The frequency shift increases with shortening laser pulse duration and laser intensity. For the rear portion of the pulse, the critical layer moves backward, causing a blue shift. The effect is more pronounced for shorter pulses and longer density scale lengths, consistent with recent experiments.
关键词： critical layer,relativistic nonlinear frequency shift,laser pulse,inhomogeneous plasma
更新于2025-09-19 17:13:59
-
Acousto-optic modulators for a controlled frequency shift of light beams in optical and microwave cold-atom frequency standards
摘要： A series of specialised acousto-optic modulators/frequency shifters based on paratellurite (TeO2) single crystals is developed for systems of laser cooling and frequency stabilisation of laser sources in optical and microwave frequency standards based on cold strontium, rubidium and caesium atoms. The methods of calculation and optimisation of the main parameters of acousto-optic modulators are considered; their basic technical characteristics are experimentally investigated in the spectral range of optical radiation 460 – 900 nm and in the frequency shift range of 5 – 400 MHz. The modulators have a high diffraction efficiency, low power consumption and the ability to work with linearly and randomly polarised optical radiation.
关键词： frequency shifter,modulator,acousto-optic diffraction,frequency stabilisation,laser cooling,frequency shift,frequency standards
更新于2025-09-16 10:30:52
-
[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Soliton Self-Frequency Shift in Mode Locked Fiber Lasers
摘要： We propose and demonstrate the soliton evolution in a mode locked Er-doped fiber laser with intra-cavity soliton self-frequency shift by numerical simulation, and analyze effects of different parameters including of pump strength, length of dispersion shift fiber (DSF), and modulation depth of saturable absorber in detail for the first time. The results show that once the stable output pulse is formed, the frequency shift amount would increase with increasing the pump strength or decreasing the length of DSF and the modulation depth.
关键词： fiber lasers,red shift,Soliton self-frequency shift,mode locked pulse
更新于2025-09-16 10:30:52
-
A Novel Optical Frequency-Hopping System Based on DFB Laser Integrated With an EA Modulator
摘要： A novel optical frequency-hopping system based on distributed feedback laser integrated with an electroabsorption modulator is proposed and demonstrated. In the proposed system, a user’s data are split into segments and modulated onto multiple optical frequency shift keying carries, therefore, a single wavelength of optical carrier only carries partial user’s data. By this way, the security of optical communication system is improved. In this paper, we demonstrate an error free transmission through 32-km single mode ?ber and 8-km dispersion compensation ?ber with 2.5 Gb/s hopping rate and 10 Gb/s data rate. Meanwhile, we also compare and analyze the performance of the proposed system with different hopping rate and data rate.
关键词： communication system security,Optical frequency hopping,optical frequency shift keying
更新于2025-09-16 10:30:52
-
[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) - Infrared 1000-nm-Supercontinuum by Means of Self-Frequency Shift of Raman Solitons Supported by Four-Wave Mixing
摘要： Infrared spectroscopy is deployed in various fields of science and technology such as organic and inorganic chemistry, monitoring of greenhouse gases, food industry, artwork conservation, and analysis of polymers and semiconductor microelectronics [1]. The supercontinuum generation based on self-frequency shift (SFS) of Raman solitons in various optical fibres is a technology to provide promising spectra for infrared spectroscopy applications. However, these spectra are restricted in range due to the limitations of Raman gain spectrum and optical absorption in silica fibres beyond the C band. Thus, they hardly spread over 300 nm if starting from around 1550 nm [2]. However, as I show here using numerical simulations of the Generalised Nonlinear Schr?dinger Equation, if the SFS of Raman solitons is supported by the effect of four-wave mixing (FWM), the range of such supercontinuum can increase up to 1000 nm counteracting the limits of Raman gain and optical absorption.
关键词： four-wave mixing,Infrared spectroscopy,self-frequency shift,Raman solitons,supercontinuum generation
更新于2025-09-16 10:30:52