Broadband EO-Comb Generation Based on Two-Stage Nonlinear System

Abstract

Optical frequency comb (OFC) has attracted growing interest in various fields, such as frequency metrology, absorption spectroscopy, and instrumental calibrations. Electrooptic modulation (EOM) is one of the main comb-generating methods with the advantageous features of adjustable repetition frequency, high optical signal-to-noise ratio, and intrinsic coherence of the comb teeth. However, the spectral range of the EO-comb is limited by the modulation depth. In this paper, a twostage nonlinear system is built to broaden a 12.5 GHz EO-comb, namely the fiber-based stage and the on-chip stage. In the fiberbased stage, the pulse width of the comb is compressed to 52 fs from ~3 ps, meanwhile, the peak power is amplified to 2053 W and the comb spectrum is moderately broadened. In the on-chip stage, the comb is further broadened by an integrated Si3N4 waveguide spanning from 1200 nm up to 2000 nm. It is worth mentioning that the characteristic absorption lines of water vapor can also be observed in the broadened spectrum. These results indicate that the built system may have great application prospects in the field of parallel gas detection.

Sub‐30‐fs fibre‐coupled electro‐optic modulation comb at 1.5 μm with a 25‐GHz repetition rate

“…Furthermore, Yu et al. generated an EO comb with an FWHM of 53 fs at a repetition rate of 12.5 GHz using the same method as in [5] and coupled it to a silicon nitride waveguide (SiNW) to generate SC light at 1200 to 2000 nm [6]. However, these experimental setups use more than 800 m of fibre and are unsuitable for microwave phase noise reduction.…”

“…Zhang et al successfully generated an all-fibre EO comb with a full width at half maximum (FWHM) of 86 fs at a 10-GHz repetition rate by using two non-linear optical mirrors (NOLM) and a highly non-linear fibre (HNLF) [5]. Furthermore, Yu et al generated an EO comb with an FWHM of 53 fs at a repetition rate of 12.5 GHz using the same method as in [5] and coupled it to a silicon nitride waveguide (SiNW) to generate SC light at 1200 to 2000 nm [6]. However, these experimental setups use more than 800 m of fibre and are unsuitable for microwave phase noise reduction.…”