Measuring Linewidth Enhancement Factor by Relaxation Oscillation Frequency in a Laser with Optical Feedback

• Main Authors: Yuxi Ruan, Bin Liu, Yanguang Yu, Jiangtao Xi, Qinghua Guo, Jun Tong
• Format: Article
• Language: English
• Published: MDPI AG 2018-11-01
• Series: Sensors
• Subjects: linewidth enhancement factor; relaxation oscillation; external optical feedback; self-mixing interferometry; laser sensors
• Online Access: https://www.mdpi.com/1424-8220/18/11/4004

This paper presents a new method for measuring the linewidth enhancement factor (alpha factor) by the relaxation oscillation (RO) frequency of a laser with external optical feedback (EOF). A measurement formula for alpha is derived which shows the alpha can be determined by only using the RO frequencies and no need to know any other parameters related to the internal or external parameters associated to the laser. Unlike the existing EOF based alpha measurement methods which require an external target has a symmetric reciprocate movement. The proposed method only needs to move the target to be in a few different positions along the light beam. Furthermore, this method also suits for the case with alpha less than 1. Both simulation and experiment are performed to verify the proposed method.