Abstract

Lasers with high optical frequency stability have played a significant role in numerous applications including metrology and spectroscopy. A laser with better frequency stability allows shorter integration time and higher accuracy. To achieve this, one of the most crucial factors is the stability of the cavity length of the laser. The length of the cavity is always disturbed by environmental noises such as acoustic or vibrational ones, and we often utilize cavity length modulators to compensate it. Piezo-electric transducers (PZTs) and electro-optic modulators (EOMs) are commonly used for this purpose. PZTs typically work up to several kHz ranges, whereas EOMs have much broader feedback bandwidth (more than several hundred kHz) and lead to much higher stability. However, we cannot apply EOMs in many cases, such as laser cavities with high-power, high-quality factor or broadband spectrum, because EOMs are used in transmissive configurations. PZTs with a mirror can be used in such cases thanks to their reflective configurations. Therefore PZTs with broad feedback bandwidth have been in great demand. The bandwidth of a PZT is restricted by mechanical resonances lying around 10 kHz to several hundred kHz, which are caused by vibration coupling with a mirror mount. To damp these resonances, various structures of the mirror mount were demonstrated [1]. However, resonances lying over the 200-kHz region have not been damped, and the resulting feedback bandwidth has not exceeded 200 kHz as well.

© 2017 IEEE