A 12.5 GHz-spaced optical frequency comb locked to a Global Positioning System disciplined oscillator for near IR spectrograph calibration is presented. The comb is generated via filtering a 250 MHz-spaced comb. Subsequent nonlinear broadening of the 12.5 GHz comb extends the wavelength range from 1380 nm to 1820 nm, providing complete coverage over the H-band transmission window of Earth s atmosphere. Finite suppression of spurious sidemodes, optical linewidth and instability of the comb have been examined to estimate potential wavelength biases in spectrograph calibration. Sidemode suppression varied between 20 and 45 dB, the optical linewidth was approximately 350 kHz at 1550 nm and the comb instability was bounded by +/- 30 kHz (5 cm/s). These results indicate this comb can support radial velocity measurements below 1 m/s.
Citation: Review of Scientific Instruments
Pub Type: Journals
mode-locked lasers, optical frequency comb, spectroscopic instrumentation