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

Abstract

We present a 100 MHz repetition rate Ybfiber-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 nonresonant 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.

Broadband cavity-enhanced ultrafast spectroscopy

“…In the present measurements, working with molecules with relatively large excitation cross sections, we obtain sufficient signal to noise without employing an enhancement cavity for the pump to boost the pump power, as was done in Reber et al 13 , but it would be relatively straightforward to implement a pump enhancement cavity if even higher sensitivity were needed. We use the residual second harmonic (4.5 W) to pump a home-built tunable synchronouslypumped optical parametric oscillator (OPO) with subsequent intracavity doubling for both the signal and idler 15 . Using the 532 nm pump as well to cover the gap near OPO degeneracy, this provides tunable combs over the range of 420-720 nm, as described in ref.…”

“…Using the 532 nm pump as well to cover the gap near OPO degeneracy, this provides tunable combs over the range of 420-720 nm, as described in ref. 15.…”

“…First of all, the OPO optical-phase transfer relations we discovered in ref. 15 necessitate that the three different combs are frequency-locked to the enhancement cavity using three different schemes with different actuators, as detailed in ref. 16.…”

“…To go from CE-TA to CE-TAS has involved considerable innovation, since many of the necessary components did not exist prior to our work. We have previously published results regarding aspects of the optical technology critical to CE-TAS, namely the development of widely tunable, low noise, high-power frequency combs 15 and the enhancement of these widely-tunable combs in a femtosecond enhancement cavity with custom mirror coatings 16 . Achieving reliable and repro-ducible transient absorption spectroscopy data with ∆ OD < 10 −9 using this optical technology has also required significant innovation which we detail in this paper, where we present the first spectroscopy results from this system.…”

Optical Frequency Combs for Molecular Spectroscopy, Kinetics, and Sensing

“…15 Difference frequency generation and optical parametric oscillation in nonlinear crystals have enabled broadband, tunable comb sources spanning visible and mid-IR wavelengths. [16][17][18][19][20][21][22][23] Production of coherent combs in the XUV has been achieved through high harmonic generation carried out in a resonant optical cavity. 24 In recent years, much work has been done to enable novel comb sources that are more compact and frequency agile than mode-locked lasers.…”