腔调谐过程中激光器中两垂直偏振光的回馈特性

腔调谐过程中同时对HeNe激光器进行光回馈，设定回馈镜驱动信号的周期远小于腔调谐信号的周期，此时便获得腔调谐过程中谐振腔中两垂直偏振光的回馈信号. 回馈的形式分为仅垂直光回馈、仅平行光回馈以及两光同时回馈三种情况. 当两光同时回馈时，两模式间的模竞争较弱，两光回馈曲线有一定的相位差，该相位差小于180°，两光总体波动幅度变化趋势相反. 当仅单偏振光回馈时，两模式间的模竞争较强，两光回馈曲线始终反相，而且两光波动幅度变化趋势相同，此时可以将两光强度信号相减以实现成倍提高回馈信号幅度，从而提高系统灵敏度. 尤其仅垂直光回馈时，两光各自光强波动幅值都较大，并且在较大的增益曲线范围内保持光强波动幅值无明显变化，该特性可用于提高回馈系统的抗干扰能力，减少因激光功率漂移而引起的错误计数.关键词：自混合干涉光回馈模竞争位移测量

Optical feedback characteristics of two orthogonally polarized light beams in a HeNe laser during cavity tuning

We can get optical feedback signals of the two orthogonally polarized light beams in a HeNe laser during the cavity tuning process when the period of the driving signal of the feedback mirror is set much shorter than that of the cavity mirror. The experiments are done under three different optical feedback conditions: only perpendicular light is fed back, only parallel light is fed back and both lights are fed back. When both lights are fed back, there is a phase delay less then 180 degrees between the two lights' intensity curves. When only one polarized light is fed back into the laser cavity, the two lights' intensity curves are inverted with respect to each other. We can subtract one light's intensity curve from the other one to improve the sensitivity of the optical feedback system. Especially when only perpendicular light is fed back, both lights' modulation amplitudes are large in a wide range of gain curve with the DC component stable. This property can be used to reduce the miscount of the system.