Optical referencing technique with CW lasers as intermediate oscillators for continuous full delay range frequency comb interferometry

TLDR

The study introduces a new referencing technique for continuous‑wave frequency‑comb spectrometry that extends the accessible delay range. The technique employs intermediate laser oscillators to overcome the delay‑range limitation of passive‑filter methods. Using these oscillators, the authors achieved continuous full‑delay‑range interferometry, demonstrating a 100 MHz (0.003 cm⁻¹) resolution, 440 SNR in 2 s, and the first single‑shot, full‑bandwidth cFTS measurement resolving 105 k spectral elements.

Abstract

This paper presents a significant advancement in the referencing technique applied to frequency comb spectrometry (cFTS) that we proposed and demonstrated recently. Based on intermediate laser oscillators, it becomes possible to access the full delay range set by the repetition rate of the frequency combs, overcoming the principal limitation observed in the method based on passive optical filters. With this new referencing technique, the maximum spectral resolution given by each comb tooth is achievable and continuous scanning will improve complex reflectometry measurements. We present a demonstration of such a high resolution cFTS system, providing a spectrometry measurement at 100 MHz of resolution (0.003 cm(-1)) with a spectral signal to noise ratio of 440 for a 2 seconds measurement time. The resulting spectrum is composed of 105 · 10(3) resolved spectral elements, each corresponding to a single pair of optical modes (one for each combs). To our knowledge, this represents the first cFTS measurement over the full spectral range of the sources in a single shot with resolved individual modes at full resolution.