1 MW Peak-Power Mamyshev Oscillator Started by a Passively Q-Switched Microchip Laser

Ultrafast fiber lasers (UFLs) have become an attractive alternative to solid-state lasers (SSL) due to their excellent beam quality, compactness, environmental stability, and easy thermal management. In the last decade, a significant research effort is spent to identify UFL architectures providing pulse energy, duration, and peak power comparable to those of complex and expensive, Ti:sapphire laser systems and semiconductor saturable absorber mirrors mode-locked, Yb-doped SSL. Lately, Mamyshev oscillators (MOs), relying on offset spectral filtering combined with nonlinear spectral broadening by self-phase modulation, emerge as a promising solution and are rapidly becoming the state of the art for high energy/peak power UFLs based on large-mode-area (LMA) fibers. The focus of this work is the first demonstration of starting of the mode-locking regime in an LMA MO with an affordable passively Q-switched microchip laser. This solution was previously demonstrated only in low-power MO based on single-mode fibers, which are intrinsically easier to seed, if compared to high-gain LMA UFLs, because of the lower amplified spontaneous emission noise floor. This starting technique in an easy-to-implement ring LMA MO at 1 mu m is tested. The oscillator provides approximate to 50 nJ pulses at 12 MHz repetition rate with a minimum pulse duration of approximate to 50 fs after compression, resulting in MW peak power. For the first time, a high power free-space/fiber Mamyshev ring oscillator, developed with commercially available elements and with a simple yet effective architecture, is reliably started by an external passively Q-switched microchip laser at 1064 nm. At 5 W incident pump power, the output pulses achieve approximate to 115 nJ, approximate to 70 nm spectral bandwidth and 50 fs compressed duration at a repetition rate of 12 MHz.image (c) 2024 WILEY-VCH GmbH