Frequency-doubled chirped-pulse dual-comb generation in the near-UV: Combined vs separated beam investigations of Rb atoms near 420 nm

TL;DR

This paper presents a novel near-UV dual-comb generation method using sum frequency generation with a comparison of combined versus separated beam configurations, demonstrating advantages in stability and power throughput for spectroscopic applications.

Contribution

It introduces a new dual-comb generation technique in the near-UV with a detailed comparison of beam configurations, highlighting improved stability and efficiency.

Findings

Combined beam method offers superior phase stability.

Separated beams enable phase retrieval.

Near-UV bandwidths reach approximately 4 cm-1.

Abstract

We describe an electro-optic dual-comb system that operates in the near-infrared (near-IR) region to generate optical frequency combs in the near-UV by sum frequency generation in two configurations. The near-IR frequency combs are generated using chirped pulses that down convert the optical information into the radio frequency (RF) domain by a difference in the chirp bandwidths. Near (UV) combs at twice the near-IR bandwidth are obtained by sum frequency generation in a nonlinear crystal and detected by a hybrid photon counting detection system. We compare the results of studies of Rb near 420 nm using two optical arrangements where the near-IR combs are mixed in the crystal as combined or as separated beams. While the latter method enables phase retrievals, the combined beam method is superior for phase stability, power throughput for detection, and ease of alignment. High order interleaving enables near-UV bandwidths near 4 cm-1 for faint photonic sensing and spectroscopic applications. The harmonic generation method is easily extendable across much of the titanium sapphire tuning range.