Er:ZBLAN Fiber-based Ultra-short Pulse Generation, Amplification and Wavelength Tuning in Mid-IR and LWIR

Passcode: CUOS

The development of intense ultrashort laser sources in the mid-infrared (mid-IR, 2-8 μm) and long-wave infrared (LWIR, 8-15 μm) is of great interest in various important research directions, including vibrational spectroscopy, remote sensing, laser particle acceleration, attoscecond pulse generation, and strong-field physics.  For those applications, the use of fiber lasers provides the advantages including low cost, compactness, maintenance-free operation, and diffraction-limited beam output, competing with other solid state laser sources. Fluoride fibers are used instead of silica fibers to build mid-IR lasers, benefiting from the much broader transmission window reaching 4 μm. To reach LWIR, using mid-IR lasers as the seed sources, comparing with near-IR lasers, has the intrinsic advantages of smaller quantum defect and potentially higher conversion efficiency, which consequently means the generation of higher energy/power of the LWIR signal.

In this thesis, we report the generation of ultrashort pulses with record high average power in combination with sub-100 fs pulse duration from a compact mid-IR fluoride fiber laser. We also report the development of a tunable mid-IR fiber laser covering 2.8-4 μm wavelength region with high conversion efficiency, using high nonlinearity fluoride fiber. We then report the demonstration of a LWIR ultrashort pulse generation scheme by the difference frequency generation (DFG) technique, using all fluoride fiber lasers operating in the mid-IR wavelength region, for the first time. This research constitutes a proof-of-principle demonstration of the signal source of an Optical Parametric Chirped-Pulse Amplification (OPCPA) system, which is recognized as a promising pathway for efficient intense few-cycle pulse generation in LWIR.

Chair: Professor Almantas Galvanauskas