线性调频激光回馈粒度探测灵敏度提升方法  

Sensitivity enhancement in laser self-mixing nano-particle sizer with linear current tuning based frequency shifting method

作　　者：寇科 王错 王晛[1] 连天虹[1] 焦明星[1] 樊毓臻 Kou Ke;Wang Cuo;Wang Xian;Lian Tian-Hong;Jiao Ming-Xing;Fan Yu-Zhen(School of Mechanical and Precision Instrument Engineering,Xi’an University of Technology,Xi’an 710048,China)

机构地区：[1]西安理工大学机械与精密仪器工程学院,西安710048

出　　处：《物理学报》2023年第16期307-314,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61803302,52205067)资助的课题.

摘　　要：激光回馈(或激光自混合干涉)技术在位移、距离、速度、振动等传统物理量测量领域具有广泛的研究和应用.近20年来,这项技术在纳米粒度检测中也展示出了巨大的前景,其测量原理是:基于激光束与照射区域每个粒子相互作用的非相干叠加,粒子直径可以通过激光回馈信号功率谱的洛伦兹拟合而求出.激光回馈粒度检测一般使用恒流驱动的半导体激光器,其信号功率谱峰会位于零频附近,只呈现出右侧部分,有些使用固体激光器的粒度传感器通过一对声光调制器进行移频,将功率谱峰搬离零频位置,但是极大地增加了系统的复杂度和费用.本文用线性调制电流驱动半导体激光器,以产生近似线性调频,从而方便地把功率谱峰搬移到任意期望的频谱位置上.此外,适当的光反馈强度下,倾斜的回馈信号条纹会导致功率谱峰产生高次谐波,这些谐波峰的频谱展宽较主峰更为明显,可以有效提高纳米粒子检测的灵敏度.本文所提出的新技术方案通过数值仿真和实验验证,有望应用在低成本、结构紧凑、高灵敏度的激光回馈粒度传感器或相关仪器中.Laser self-mixing interferometry(SMI)has been widely researched and applied to the field of traditional physical quantities(such as displacement,distance,velocity and vibration)detection due to the well-known merits of compact structure,low-cost and high sensitivity,additionally,it has also shown great potential in nano-particle sizing during the last two decades,primarily depending on the incoherent stochastic superposition of laser beam’s interaction with each particle in the illuminating volume,and the particle diameter can be determined from the power spectra of self-mixed signals through Lorentz fitting.SMI particle sensing generally uses constant current driving laser diodes(LD),so the power spectrum peak occurs around zero-frequency and merely exhibits the right-hand half.Some other particle sensors using solid-state lasers(SSL),however,prefer to employ a pair of acousto-optic modulators(AOM)as frequency shifters,which pronouncedly increases the complexity and the cost of the whole system.In this paper,linear modulation current is applied to a LD to achieve laser frequency tuning and conveniently shift the concerned Lorentz peak to any desired spectrum position.Moreover,higher-order harmonics of the shifted Lorentz peak,arising from intrinsically tilted SMI fringes,exhibit wider spectrum broadening than the main peak and can be employed to improve the sensitivity in nano-particle recognition.The technique proposed has been validated by simulation and experimental results,and it is beneficial to developing low-cost,compact and highly sensitive SMI particle sensors or instruments.

关 键 词：激光回馈 线性调频 粒度检测 高次谐波 灵敏度 

分 类 号：TN249[电子电信—物理电子学]