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.

Response Time

The PD signal is transmitted when the 1654nm laser is swept. 

Note that no careful mode matching is performed at this time, so the peak interval is about 1.5GHz

The peak a is fitted, and the peak position and width are 99.747 and 0.071 respectively

The peak b is fitted, and the peak position and width are 134.567 and 0.069 respectively. 

The overall precision at 1654nm is about 497.4