Intra-Cavity Frequency-Doubled VECSEL System for Narrow Linewidth Rydberg EIT Spectroscopy

TL;DR

This paper demonstrates a narrow-linewidth intra-cavity frequency-doubled VECSEL system capable of high-power ultraviolet light generation, with stable frequency and successful Rydberg EIT spectroscopy, advancing quantum technology applications.

Contribution

It introduces a high-power, narrow-linewidth intra-cavity frequency-doubled VECSEL with verified stability and suitability for precision spectroscopy and quantum applications.

Findings

Fundamental linewidth of 5.3 kHz measured

Total linewidth of 23 kHz observed

Successful Rydberg EIT spectroscopy with 3.5 MHz FWHM

Abstract

Vertical external-cavity surface-emitting lasers (VECSELs) augmented by intra-cavity nonlinear optical frequency conversion have emerged as an attractive light source of ultraviolet to visible light for demanding scientific applications, relative to other laser technologies. They offer high power, low phase noise, wide frequency tunability, and excellent beam quality in a simple and inexpensive system architecture. Here, we characterize the frequency stability of an intra-cavity frequency-doubled VECSEL with 690 mW of output power at 475 nm using the delayed self-heterodyne technique and direct comparison with a commercial external-cavity diode laser (ECDL). We measure the fundamental's Lorentzian linewidth to be $2\pi\times5.3(2)$ kHz, and the total linewidth to be $2\pi\times23(2)$ kHz. In addition, we perform Rydberg-state spectroscopy via electromagnetically induced transparency (EIT), observing narrow 3.5 MHz full-width half-maximum EIT. By doing so, we demonstrate that intra-cavity frequency-doubled VECSELs can perform precision spectroscopy at the MHz level, and are a promising tool for contemporary, and future, quantum technologies.