Fabry–Pérot filter cavities for wide-spaced frequency combs with large spectral bandwidth

Abstract

We use low-finesse Fabry-Pérot cavities in series to generate frequency combs with a large mode spacing in a way that allows its application to a large optical bandwidth. The attenuation of laser modes closest to the pass bands of the cavity exceeds 70 dB for a filter ratio of m = 20 relative to the resonant modes centered within the pass bands. We also identify the best cavity geometry to suppress spurious transmission of higher order transversal modes. Such a thinned out frequency comb can be used to calibrate traditional spectrographs for precision astronomy. In the time domain mode filtering generates a pulse train with a multiplied repetition rate. High-fidelity filtering, as described here, implies small variations of the pulse energies.

A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

“…By using two cavities we obtain a suppression of the nearest 250 MHz sidemodes by more than 60 dB (Steinmetz et al, 2009). The plane mirrors of the cavities are piezo-driven for very fast adjustment of the resonator length.…”

Sub-100 attoseconds stability optics-to-microwave synchronization

“…At high Fourier frequencies, improving the white noise background would require a better sig- nal to noise ratio which may be accessible by increasing the saturation power of the photodetector and/or multiplying the repetition rate. Although it seems hard with the present FOFC technology to go much beyond a few hundreds MHz repetition rate (except with harmonically mode-locked lasers), pulse multiplication by resonant Fabry-Perot cavity [15,16] is a very promising technology which may reasonably be implemented for our FOFCs.…”

Continuous-wave femtosecond lasers

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