Electro-Optic Comb Generation Via Cascaded Harmonic Modulation

TL;DR

This paper presents a novel electro-optic frequency comb with over 120 GHz bandwidth and a 75 MHz repetition rate, achieved through cascaded modulators driven at sequential harmonics, offering tunability and stability for various applications.

Contribution

The work introduces a new architecture for electro-optic comb generation using cascaded modulators at different harmonics, enabling wide bandwidth and flexible repetition rates without hardware changes.

Findings

Achieved >120 GHz optical bandwidth.

Demonstrated stable 75 MHz repetition rate.

Flexible modulation at various harmonics.

Abstract

Electro-optical modulation of a continuous wave laser is a highly stable way to generate frequency combs, gaining popularity in telecommunication and spectroscopic applications. These combs are generated by modulating non-linear electro-optic crystals with radio frequencies, creating equally spaced side-bands centered around the single-frequency seed laser. Electro-optic frequency comb architectures often choose between optical bandwidth (cascaded GHz combs) or higher mode density (chirped RF generation). This work demonstrates an electro-optic frequency comb with > 120 GHz of bandwidth and a 75 MHz repetition rate. The comb has three cascaded electro-optic modulators driven at sequentially lower harmonics, the last megahertz modulation dictating the repetition rate. This architecture can modulate at any individual harmonic and repetition rate without changes to the components. This comb can be used in any applications where a stable and tunable repetition rate is needed.