基于腔内电光调制的染料激光频率噪声压制

Frequency Noise Suppression of a Dye Laser Based on Intracavity Electro-Optic Modulator

采用Pound-Drever-Hall锁频方法对连续波可调谐染料激光器的频率噪声进行了压制。设计和组装了一种小型腔内电光调制器作为快速频率调整的执行机构。详细讨论了腔内电光调制器的设计参数并给出了两种常用电光晶体的机械谐振的测量结果。以该电光调制器和激光腔镜上的压电陶瓷作为频率反馈控制的执行机构将染料激光锁定在一个法布里-珀罗腔上。当只采用压电陶瓷时激光频率噪声在100Hz附近被降低了3个数量级,进一步加入电光调制控制环路后,在100Hz到50kHz范围内激光频率噪声能进一步减小4/5。经过频率噪声的压制后激光光谱线宽从自由运转时的2.2MHz降低到了10kHz。

The frequency noise of a continuous-wave tunable dye laser is suppressed by using the Pound-Drever-Hall frequency locking method. To cope with relatively large high-frequency components in the dye laser frequency noise, a compact intracavity electro-optic modulator that serves as a fast frequency actuator is designed and assembled. The design parameters of the modulator are discussed in detail and the experimental data on the mechanical resonances of two commonly used electro-optic crystals are given. The dye laser is locked to a Fabry-Perot cavity by using the intracavity electro-optic modulator and piezoelectric transducers installed on the cavity mirrors. With only piezoelectric actuators the laser frequency noise is reduced by three orders of magnitude at 100 Hz and the noise is further suppressed by four-fifths from 100 Hz to 50 kHz with a combination of piezoelectric actuators and the intracavity electro-optic modulator. With the suppression of frequency noise implemented, the 2.2 MHz free-running laser linewidth is reduced to 10 kHz.