500 GHz宽带双偏振光学频率梳的产生

Generation of 500-GHz Broadband Dual-Polarization Optical Frequency Comb

提出了一种基于光电反馈产生500 GHz宽带双偏振光学频率梳的方案。该方案基于光电环路反馈1550 nm垂直腔面发射激光器,采用自旋反转模型,利用四阶龙格-库塔算法数值仿真研究了光电反馈参数对光学频率梳特性的影响。研究结果表明:通过光电反馈参数的调节可以控制1550 nm垂直腔面发射激光器输出的偏振状态,可实现Y偏振和X偏振光学频率梳的转换。此外,研究发现,在特定的光电反馈参数条件下,可获得Y偏振和X偏振同时存在的双偏振光学频率梳。并且在一定的光电反馈参数范围内,两个偏振方向的光学频率梳的光谱带宽都会随着光电反馈系数的增加而增大,相应的功率谱会随光电反馈系数的增加而变得越来越平坦。通过光电反馈系数及反馈时间的调节,获得了谱线平坦、梳线纯净、谱带超宽的光学频率梳,在10 dB幅度范围内Y偏振光学频率梳的光谱带宽可达250 GHz,X偏振光学频率梳的光谱带宽可达500 GHz。

Objective Optical frequency combs(OFC)consist of a series of evenly spaced discrete spectral components that maintain high spectral coherence.It can be applied in many fields,such as metrology,spectroscopy,optical arbitrary waveform generation,THz generation,microwave photonics,and optical communications.Among the available optical comb technologies,OFC based on semiconductor lasers provides suitable combs with competitive costs and efficiency.Vertical-cavity surface-emitting laser(VCSEL)is a single-longitudinal mode semiconductor laser.Compared with an edge emitter,VCSEL has some advantages,such as on-wafe test capability,lower energy consumption,lower manufacturing cost,and circular output beam.VCSEL can emit in two orthogonal linear polarization modes.Polarization switching between these modes can be found when changing the temperature or bias current applied to the VCSEL.These properties make them appropriate for OFC generation.Dual-polarization OFC-based VCSEL can be generated due to the special polarization properties.Further efforts are required to improve OFC-based on VCSEL,especially to expand the optical span while maintaining the existing advantages.In this study,we proposed a scheme for generating broadband dual-polarization OFC based on a 1550-nm VCSEL under optoelectronic feedback,opening perspectives for polarization-sensitive sensing and multicarriers optical sources for polarization-division multiplexing optical communications.Methods We proposed and analyzed theoretically a scheme for generating a 500-GHz dual-polarization optical frequency comb based on a 1550-nm VCSEL under optoelectronic feedback.Besides,we numerically investigated the influences of optoelectronic feedback parameters on the performances of the generated optical frequency comb.The proposed model considered the optoelectronic feedback based on the rate equations of the spin-flip model of 1550-nm VCSEL.First,we proposed a schematic diagram of a broadband dual-polarization OFC generation based on a 1550-nm VCSEL under optoelectronic feedback.Then,we analyzed the output power versus normalized bias current curves of the two modes with orthogonal polarizations of the free-running 1550-nm VCSEL that is without optoelectronic feedback.After that,optoelectronic feedback effects on the polarization dynamics of 1550-nm VCSEL under different optoelectronic feedback parameters are theoretically investigated using the spin-flip model.In the next step,we analyzed the time series and optical spectra of the two linear polarization modes with orthogonal directions of 1550-nm VCSEL under a certain normalized bias current and optoelectronic feedback time with different optoelectronic feedback coefficient values.In addition,we analyzed the optical and power spectra of the two linear polarization mode outputs of 1550-nm VCSEL with different optoelectronic feedback coefficients.Results and Discussions The results showed that two linear polarization modes with orthogonal directions of the 1550-nm VCSEL under optoelectronic feedback can be controlled by adjusting the optoelectronic feedback parameters.When the bias current or optoelectronic feedback parameters are changed under 1550-nm VCSEL,the polarization conversion of the Y-and X-polarization occurs(Fig.3).Besides,we obtained that the dual-polarization optical frequency comb with Y-and X-polarization can be achieved under certain conditions of optoelectronic feedback parameters(Fig.4).Within a certain range of optoelectronic feedback parameters,the optical spectral bandwidth of the Y-and X-polarization optical frequency comb increases with an increase in optoelectronic feedback coefficient(Fig.5),and the corresponding power spectrum becomes flatter with an increase in optoelectronic feedback coefficient(Fig.6).By adjusting the optoelectronic feedback coefficient and time,we obtained broadband dual-polarization optical frequency comb with flat spectral lines,pure comb lines.The spectral widths of the Y-and X-polarization optical frequency combs were more than 250 and 500 GHz within the amplitude range of 10 dB,respectively(Fig.5).Conclusions In this study,we proposed and analyzed theoretically a novel scheme for generating a 500-GHz dual-polarization optical frequency comb based on a 1550-nm VCSEL under optoelectronic feedback.It is shown that two orthogonal linear polarization optical frequency combs can be obtained and have comparable span and power under certain optoelectronic feedback conditions.The 10-dB spectral width of optical frequency combs of the Y-and X-polarization larger than 250 and 500 GHz can be achieved in the 1550-nm VCSEL subject to optoelectronic feedback under certain optoelectronic feedback parameter conditions,respectively.An appropriate increase in optoelectronic feedback coefficient in 1550-nm VCSEL can increase 10-dB spectral width.This increase is essential for enhancing the performance of OFCs generated by 1550-nm VCSEL under optoelectronic feedback for polarization-sensitive sensing and polarization-division multiplexing optical communications.