- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Large-Dynamic Frequency Response Measurement for Broadband Electro-Optic Phase Modulators
摘要： A novel method for characterizing the frequency responses of broadband electro-optic phase modulators (PMs) by employing stimulated Brillouin scattering (SBS) is proposed and experimentally demonstrated. In the proposed method, the SBS amplifies the +1st-order sideband and attenuates the -1st-order sideband of the phase-modulated signal from a PM under test. Thereby, the phase-modulated signal is converted into an optical single-sideband (OSSB) modulation signal. After square-law photodetection, the overall frequency responses are obtained. Removing the frequency responses of the SBS gain and the photodetector (PD) from the overall responses, the responses of the PM are thus achieved. Benefitting from the amplification of the SBS, the proposed method possesses a large dynamic range. Sub-Hz resolution and broadband measurement range are also achievable. A commercial broadband PM is experimentally characterized from 10 MHz to 50 GHz with a resolution of 5 MHz. According to the amplification of the SBS, the dynamic range is enhanced by 17.74 dB. The measurement result is verified by the conventional method utilizing optical spectrum analysis.
关键词： stimulated Brillouin scattering,Electrooptic modulation,Phase modulation,microwave photonics,optical variables measurement
更新于2025-11-28 14:24:03
-
Self-generating Brillouin fiber laser using highly nonlinear hafnium bismuth erbium-doped fiber
摘要： A compact Brillouin fiber laser (BFL) utilizing a newly developed hafnium bismuth erbium-doped fiber (HB-EDF), which functions as both the Brillouin and linear gain media, is realized in the absence of Brillouin pump. It is achieved by the self-Brillouin generation from a 0.2 m length of HB-EDF with high nonlinearity in a laser cavity. The self-generating BFL was obtained in both ring and linear laser cavities. Compared to the ring cavity, the BFL in the linear cavity produced more Brillouin stokes at a lower pump threshold. In the experiment, an eight-line comb with average spacing of 0.087 nm was generated at the HB-EDF pump power of 75.27 mW. This compact BFL has total cavity length of less than 0.5 m, and thus, this is the shortest gain medium reported.
关键词： hafnium bismuth erbium-doped fiber,self-generating Brillouin fiber laser,stimulated Brillouin scattering
更新于2025-11-28 14:23:57
-
Tunable self-excited multiwavelength Brillouin-erbium fiber laser based on a variable temperature sensor
摘要： We propose and demonstrate a tunable self-excited multiwavelength Brillouin-erbium fiber laser based on a novel in-line Mach–Zehnder interferometer sensor (NMZIS) with variable temperature. The configuration of the NMZIS is a section of uncoated single-mode fiber sandwiched between an up-taper and multimode fiber. With the temperature changing from 30 °C to 90 °C, the transmission spectrum of the NMZIS shifts towards longer wavelengths. By embedding the NMZIS to act as a fiber filter in the ring cavity, the wavelength of the output multiwavelength comb is tuned from 1552.35 to 1564.48 nm. The corresponding generation of 21 Brillouin–Stokes lines with 25 dB optical signal-to-noise ratio is achieved.
关键词： Brillouin-erbium fibre laser (BEFL),tunable,self-excited
更新于2025-11-28 14:23:57
-
Widely tunable single bandpass microwave photonic filter based on dual-fiber stimulated Brillouin scattering
摘要： A new technique to achieve a single bandpass microwave photonic filter (MPF) with wide tunability based on stimulated Brillouin scattering is proposed. The MPF cascades the Brillouin frequency shifter and amplification based on a dual-fiber structure. The experimental results present a single bandpass MPF located at 21.4 GHz with a 3-dB bandwidth of 38 MHz and an out-of-band rejection ratio over 30 dB. The proposed single bandpass MPF also successfully demonstrates a wide-band tuning over 40 GHz, which is achieved by employing a frequency shifter based on carrier suppressed single-sideband modulation scheme in the structure.
关键词： Brillouin frequency shift,stimulated Brillouin scattering,fiber,microwave photonic filter,carrier suppressed single-sideband modulation
更新于2025-09-23 15:23:52
-
[IEEE 2018 IEEE 7th International Conference on Photonics (ICP) - Kuah (2018.4.9-2018.4.11)] 2018 IEEE 7th International Conference on Photonics (ICP) - Differential Cross Spectrum Technique for Improving the Spatial Resolution of BOTDR Sensor
摘要： We propose a technique in BOTDR fiber sensor to generate a pair of pulsed probes via intensity modulation scheme for measuring distributed strain at high spatial resolution. The first probe consists of a long- and short duration of pulses separated by a short interval. The second probe only has the long pulse of the first probe. Introducing FFT in correlating the backscattered signals sampled by wide and narrow window functions for each probe gives narrow Brillouin spectrum width. The subtraction of the correlated signals obtained by the two probes results in high spatial resolution measurement. The intensity modulation makes it easier to generate the pair of pulsed probes having the same waveform of the long pulse and to obtain the results according to the measurement principle. We have achieved 0.2 m spatial resolution and 3.2 MHz Brillouin frequency accuracy in measuring a 350 m fiber.
关键词： BOTDR,spatial resolution,distributed fiber sensor,Brillouin frequency shift
更新于2025-09-23 15:23:52
-
Instantaneous microwave frequency measurement with high-resolution based on stimulated Brillouin scattering
摘要： A novel photonic method of instantaneous microwave frequency measurement (IMFM) based on Stimulated Brillouin scattering (SBS) is proposed. The principle of the technique is the employment of SBS effect to amplify/attenuate two adjacent frequency components, which result in a definite amplitude comparison function (ACF). Using this technique, the frequency of an unknown RF signal can be precisely obtained. Experimental results show the measurement capability of the proposed method over a frequency range of 0.47–23 GHz with a higher resolution of 8 MHz.
关键词： Amplitude comparison functions,Microwave photonics,Instantaneous microwave frequency measurement,Stimulated Brillouin scattering
更新于2025-09-23 15:23:52
-
Valley engineering by strain in Kekulé-distorted graphene
摘要： A Kekulé bond texture in graphene modi?es the electronic band structure by folding the Brillouin zone and bringing the two inequivalent Dirac points to the center. This can result in the opening of a gap (Kek-O) or the locking of the valley degree of freedom with the direction of motion (Kek-Y). We analyze the effects of uniaxial strain on the band structure of Kekulé-distorted graphene for both textures. Using a tight-binding approach, we introduce strain by considering the hopping renormalization and corresponding geometrical modi?cations of the Brillouin zone. We numerically evaluate the dispersion relation and present analytical expressions for the low-energy limit. Our results indicate the emergence of a Zeeman-like term due to the coupling of the pseudospin with the pseudomagnetic strain potential which separates the valleys by moving them in opposite directions away from the center of the Brillouin zone. For the Kek-O phase, this results in a competition between the Kekulé parameter that opens a gap and the magnitude of strain which closes it, while for the Kek-Y phase, it results in a superposition of two shifted Dirac cones. As the Dirac cones are much closer in the superlattice reciprocal space than in pristine graphene, we propose strain as a control parameter for intervalley scattering.
关键词： Brillouin zone,tight-binding,strain,graphene,valley engineering,Kekulé distortion
更新于2025-09-23 15:22:29
-
Monitoring of Film Qualities of Amorphous SiO2 films/Si(100) Substrates by Measuring Bulk and Surface Acoustic Waves in Terms of Brillouin Spectroscopy
摘要： Acoustic properties of amorphous SiO2 thin films deposited on the Si(100) substrate were investigated by using Brillouin spectroscopy. The Brillouin spectrum was obtained by tilting the sample to investigate both the longitudinal acoustic (LA) mode and the surface acoustic wave (SAW) modes. Sound velocities of both modes, the two elastic moduli (longitudinal and shear moduli), and the Poisson ratio of the film could be obtained by combining the Brillouin data and the measured refractive index. The longitudinal sound velocity and the longitudinal elastic modulus increased with increasing Ar ratio in the Ar:O2 gas mixture, which was attributed to the better stoichiometry of the film grown at higher Ar ratio.
关键词： Brillouin scattering,Surface acoustic wave,SiO2 film
更新于2025-09-23 15:22:29
-
Influence of the capping layer material on the interfacial Dzyaloshinskii-Moriya interaction in Pt/Co/capping layer structures probed by Brillouin light scattering<sup></sup>
摘要： Influence of the capping layer material on the interfacial Dzyaloshinskii-Moriya interaction in Pt/Co/capping layer structures probed by Brillouin light scattering. Co ultrathin films, of various thicknesses (0.8 nm ≤ tCo ≤ 2.5 nm), have been grown by sputtering on Si substrates, using Pt buffer layers and different capping layers (Cu, Ir, MgO and Pt). The x-ray diffraction revealed that our films have a (111) out-of-plane texture with various degrees of strains. Their magnetic properties have been studied by vibrating sample magnetometry (VSM) and Brillouin light scattering (BLS) in the Damon-Eshbach geometry. VSM characterizations revealed that films with Co thickness below (above) the spin reorientation transition thickness, which is capping layer dependent, are perpendicularly (in-plane) magnetized, suggesting the existence of an interface anisotropy. The magnetic dead layer has been taken into account to precisely determine the surface anisotropy constant was found to be 1.42 ± 0.02 erg/cm2 and of 1.33 ± 0.02 erg/cm2 for the Pt/Co/Cu and Pt/Co/Ir samples, respectively, suggesting that it is due to the Pt/Co interface and that the top Co/Cu or Co/Ir interfaces have a negligible contribution. A lower value of 1.07 ± 0.02 erg/cm2 has been obtained for Pt/Co/MgO most probably due to over-oxidation of Co at the Co/MgO interface. The BLS measurements revealed a pronounced nonreciprocal spin waves propagation, due to the interfacial Dzyaloshinskii-Moriya interaction (iDMI) induced by Pt interface with Co, which increases with decreasing Co thickness. The surface iDMI constant Ds estimated at -0.8 pJ/m, -1.05 pJ/m and –0.95 pJ/m, respectively for Pt/Co/Ir, Pt/Co/Cu and Pt/Co/MgO for the samples where a linear thickness dependence of the effective iDMI constant has been observed.
关键词： Dzyaloshinskii-Moriya interaction,Brillouin light scattering,spin waves and Perpendicular magnetic anisotropy,Interface effects
更新于2025-09-23 15:22:29
-
Cross correlation peak-seeking technique of BOTDR based on the incomplete Brillouin spectrum
摘要： Considered the limitation of sweeping frequency technique, Brillouin optical time domain reflectometer (BOTDR) can only perceive slow external interference. It greatly limits the scope of application. For perceiving rapid external interference, a method of cross correlation peak-seeking technique based on incomplete Brillouin spectrum (IBS) is proposed, and the feasibility of the method is verified under the background of the monitoring of sound barriers along the high-speed railway. The numerical simulation results indicate that the probability that obtains an accurate peak frequency error within the 0.50 MHz can reach 49/50, when frequency interval for sweeping is 5 MHz and number of splicing IBS is 80. In addition, to select the optimal parameters of the system, we also take a further analysis on the effect of the splicing times and the frequency interval for sweeping on the peak detection accuracy. This method is significant to extend the application of BOTDR from slow changing fields to rapid changing fields.
关键词： Optical time domain reflectometry,Brillouin scattering,Optical fiber measurement applications
更新于2025-09-23 15:22:29