This high-precision spectrometer is used to examine the fine structure of the spectral characteristics of continuous-wave lasers. The spectrometer is based on a confocal Fabry-Perot (F-P) cavity, which contains two high-reflectivity mirrors. By using a piezoelectric transducer to change the spacing between the mirrors, the cavity can act as an extremely narrow bandpass filter. After measuring the free spectral range (FSR) of the confocal cavity, the time base of an oscilloscope can be calibrated to enable quantitative measurement of the laser line shape. According to the design of the confocal cavity, the distance d between the mirrors is equal to the radius R, allowing the laser beam to be easily aligned. This series of models is compatible with Thorlabs Piezo drivers.

Specification

Response Time

Transmitted PD signal when using 1063nm laser sweep. Note that no careful mode matching is performed at this time, So the peak spacing is about 1.5GHz.

The peak a was fitted and the peak position and width were 59.25 and 0.198 respectively.

The peak b was fitted, and the peak position and width were found to be 98.42 and 0.185 respectively. 

The overall result shows that the finesse at 1063 nm is about 204.5