Spacing and Wavelength Tunable Frequency Comb

Abstract

Optical frequency combs are increasingly used in applications such as optical communications, radio signal processing, and dual-comb spectroscopy. Many of these applications require a broad, flat spectrum with tunable center wavelength and tone spacing, while maintaining a consistent spectral profile. However, most existing OFC generators either lack tunability or cannot preserve their spectral shape during tuning. In this paper, we demonstrate a cavity-less OFC system based on an electro-optic comb combined with parametric spectral broadening, achieving tone spacing tunability from 25 to 32 GHz and wavelength tunability from 1548 to 1568 nm. Our OFC features high output power (greater than 2 W), broad bandwidth (greater than 90 nm), high optical signal-to-noise ratio (OSNR greater than 25 dB), and, critically, a preserved spectral profile. We show that this consistent spectral shape can be maintained by primarily adjusting the RF drive power and the gain of the optical amplifiers. We also provide a quantitative analysis of the spectral profile variations during tuning.