# Tunable visible frequency combs from a Yb-fiber-laser-pumped optical parametric oscillator

## TL;DR

This paper demonstrates a tunable visible frequency comb source using a Yb-fiber-laser-pumped optical parametric oscillator, achieving broad spectral coverage, high power, and phase noise control for advanced optical applications.

## Contribution

It introduces a novel tunable visible frequency comb system based on a synchronously pumped OPO with intracavity doubling, covering 420-700 nm with high power and phase stability.

## Key findings

- Achieved nearly continuous tuning over 420-700 nm range.
- Generated pulse durations below 150 fs without external compression.
- Demonstrated phase noise transfer from pump to idler comb.

## Abstract

We present a 100 MHz repetition rate Yb-fiber-laser-pumped synchronously pumped optical parametric oscillator (SPOPO) delivering tunable frequency combs covering almost the entire visible spectral range. By intracavity doubling both the signal and idler combs and using collinear residual pump light, nearly continuous tuning over the range of 420-700 nm is achieved with only small gaps near the OPO degeneracy condition. Output powers range from 10 mW to 200 mW, depending on wavelength, with pulse durations below 150 fs without external compression. Frequency locking of all three collinearly outcoupled combs (pump, doubled signal, and doubled idler) to a femtosecond enhancement cavity facilitates direct comparison of their optical phase noise and phase modulation transfer functions. In the singly-resonant OPO, optical phase modulation of the pump comb is transferred nearly completely to the non-resonant idler comb. This results in a resonant signal comb with reduced optical phase noise and also enables high-bandwidth modulation on the idler comb via phase modulation of the pump.