Sub-50 fs pulses around 2070 nm from a synchronously-pumped, degenerate OPO

Alireza Marandi,Robert L Byer,Charles W Rudy,Jian Liu,Stephen J Wolf,Kirk A Ingold,Konstantin L Vodopyanov,Lihmei Yang,Peng Wan

doi:10.1364/oe.20.027589

Abstract

We report generation of 48 fs pulses at a center wavelength of 2070 nm using a degenerate optical parametric oscillator (OPO) synchronously-pumped with a commercially available 36-MHz, femtosecond, mode-locked, Yb-doped fiber laser. The spectral bandwidth of the output is ~137 nm, corresponding to a theoretical, transform-limited pulse width of 33 fs. The threshold of the OPO is less than 10 mW of average pump power. By tuning the cavity length, the output spectrum covers a spectral width of more than 400 nm, limited only by the bandwidth of the cavity mirrors.

Highlights

There are numerous applications for pulsed 2-μm sources, including laser driven particle acceleration [1], mid- to far-IR spectroscopy [2], “eye-safer” remote sensing [3, 4], high harmonic generation [5], and medical applications, due to the proximity to strong water absorption lines
While development of thulium-doped fiber lasers is still progressing, a clean transfer of the properties of commercial ytterbium-doped fiber lasers to the 2-μm wavelength range can be performed via a degenerate, synchronously- pumped optical parametric oscillator (OPO) with a magnesium oxide-doped, periodically-poled, lithium niobate crystal (MgO:PPLN)—already a mature technology [6]
Since the output is intrinsically phase- and frequency-locked to the pump source, commercially-available frequency comb sources can be transferred to longer wavelengths [9]. Unlike these previous OPOs, the zero dispersion point of MgO:PPLN at 1.95 μm is near the center wavelength of the OPO, which makes dispersion compensation unnecessary to produce sub-50 fs pulses

Summary

Introduction

There are numerous applications for pulsed 2-μm sources, including laser driven particle acceleration [1], mid- to far-IR spectroscopy [2], “eye-safer” remote sensing [3, 4], high harmonic generation [5], and medical applications, due to the proximity to strong water absorption lines. While development of thulium-doped fiber lasers is still progressing, a clean transfer of the properties of commercial ytterbium-doped fiber lasers to the 2-μm wavelength range can be performed via a degenerate, synchronously- (sync-) pumped OPO with a magnesium oxide-doped, periodically-poled, lithium niobate crystal (MgO:PPLN)—already a mature technology [6]. This concept has been demonstrated at several other pump wavelengths, including 775 nm [7], 1550 nm [2], and 2 μm [8]. Since the degenerate OPO has a considerably broad parametric gain bandwidth, intracavity dispersion compensation could allow the OPO to surpass the pulse width record while maintaining a relatively straightforward system

Background

Results

Conclusions and future work