摘要
波长调谐激光器广泛应用于精密干涉测量、超稳激光器等领域.激光器波长调谐精度、稳频精度是表征其性能的重要参数.为提高激光器调谐精度、稳频精度,常采用双光路进行闭环控制,如饱和吸收空间稳频光路,控制光路探测的信噪比是决定控制精度的重要参数.研究影响控制光路探测信噪比的相关参数,给出相应的影响关系,对进一步提升激光器调谐精度、稳频精度具有重要的工程应用价值.本文理论推导了光学器件核心指标、系统杂散光等参数与探测信噪比之间的相互关系,搭建了基于饱和吸收的反馈稳频激光系统.实验结果表明由于强度噪声的存在,探测器信噪比降低至15 dB且波形严重失真,通过偏振态控制可将信噪比提升至31 dB且波形良好.通过控制变量实验,验证了理论研究的正确性,该研究能够作为稳频控制光路光学器件选型、系统参数设计的依据.
Wavelength-tunable lasers play a crucial role in fields such as precision interferometry and ultra-stable laser applications.The precision of wavelength tuning and the accuracy of frequency stabilization in lasers are the key indicators of their performance.To improve these performance,closed-loop control with dual-beam paths,such as saturated absorption spectrum spatial stabilization,is commonly utilized.The signal-to-noise ratio(SNR)of the control beam detection significantly affects the control precision.Investigating the parameters that influence this SNR and analyzing their relationships are of great engineering significance for further improving the tuning precision and frequency stabilization accuracy of lasers.To increase the SNR,this work examines intensity noise in wavelength-modulation systems based on the polarizer-phase-delay-polarizer model.A polarization beam splitter(PBS)cannot achieve a zero polarization extinction ratio(PER),thus introducing intensity noise from the interference between p and s polarization light.Additionally,non-ideal stray light,such as back-reflected and scattered light from optical components,further reduces the SNR of the detection signal when it converges on the detector’s active area.This work carries out a detailed analysis of these two types of noise,exploring the effects of factors such as PER,wavelength-modulation range,beam diameter,laser polarization direction,and modulation frequency.Based on the theoretical analysis,it also simulates optical phenomena involving half-wave plates with different tilt angles and rotation angles,as well as dual-frequency Gaussian elliptically polarized light under various modulation parameters.The theoretical analysis indicates that the intensities of p and s polarization light undergo periodic variations as the angle between the half-wave plate’s optical axis and the PBS’s slow-axis direction,as well as the angle between the linear-polarization direction and the half-wave plate’s optical axis,changes.The extreme positions of these intensities move with the PER changing.At certain specific angles,destructive interference leads to extremely low intensities in both transmitted and reflected light.Furthermore,when the detector receives stray light of multiple frequencies,the synthesized phase varies periodically with wavelength tuning.This means that over time(corresponding to tuning the center wavelength to different values),the interference intensity exhibits periodic changes from constructive interference to destructive interference and then to constructive interference.Consequently,abnormal dips and peaks may appear in the optical signal intensity.A 633-B-A81-SA-PZT laser from LD-PD INC with a 10 mW output is used in the experiment.A true zero-order half-wave plate model centered at 633 nm is adopted in the simulation.The laser wavelength is tunable in the range of 633 nm±10 pm,and 10 kHz sine-wave current modulation is used,with a wavelength-current tuning coefficient of 1 pm/mA.After an isolator,a 90∶10 coupler splits the beam into a 9 mW output and a 1 mW experiment beam,which is collimated and adjusted by a polarizer,a true zero-order half-wave plate,and a PBS to set the ratio of p light power to s light power.Two Thorlabs FDS100 detectors capture the beams,with signals collected via a data acquisition card.The PD1 and PD2 signals show significant differences under certain conditions,and the p and s light signals vary periodically with half-wave plate rotating.Adding a polarizer at the laser exit and adjusting its angle can improve signal consistency.After alignment,the SNR increases from 10 dB to 31 dB.In this study,wavelength of a 633 nm semiconductor laser is tuned by using a saturated absorption spectrum ring light path.Under different modulation conditions,inconsistencies in the intensity signals of two beams are observed.Polarization control increases the SNR to 31 dB,confirming the theoretical model.Additionally,time domain analysis of stray light from the wavelength-tuned source shows that reducing the wavelength tuning range and modulation frequency can effectively suppress high frequency noise.
作者
吴育鹏
马凯
孔新新
伍洲
张文喜
WU Yupeng;MA Kai;KONG Xinxin;WU Zhou;ZHANG Wenxi(Aerospace Information Research Institute,Chinese Academy of Sciences,Beijing 100094,China;School of Optoelectronics,University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《物理学报》
北大核心
2025年第16期246-258,共13页
Acta Physica Sinica
基金
中国科学院青年创新促进会(批准号:2023132)资助的课题。
关键词
激光器与激光光学
波长调谐
椭圆光干涉
半导体激光器
lasers and laser optics
wavelength modulation
elliptical light interference
semiconductor laser
作者简介
通信作者:张文喜,E-mail:zhangwx@aircas.ac.cn。
