PhD thesis supervisor: dr. Aleksej Rodin (apply for recommendation)
Gain-switched operation coupled with nonlinear scattering methods for pico- and femtosecond pulse generation across the near and mid-IR
Alongside the widely used and wellstudied methods for generating ultrashort laser pulses, such as mode-locking (via Kerrlens or SESAM) and extreme cavitylength reduction (microchip Qswitched lasers), there exist far more costeffective approaches based on SBS-compression as well as gain switching operation. Although unsurpassed in terms of achievable output energy without resorting to bulky regenerative amplifiers, SBS-compression falls short of the gainswitching technique in both the minimum attainable pulse width (<50 ps) and the maximum repetition rate (>10 kHz). From this perspective, gain‑switched operation near the oscillator threshold remains insufficiently explored. Its practical implementation is complicated by the requirement for high‑energy pump pulses that are much shorter than the thermalization time in laser diodes, or by the need to employ a pump laser whose wavelength matches the absorption band of the gain‑switched medium. This study aims to investigate advanced gainswitched configurations coupled with nonlinear optics phenomena, such as stimulated Raman scattering (SRS) and supercontinuum generation to achieve high-energy femtosecond output pulses. Backward SRS-compression enables single‑picosecond pulses, with further transfer into the femtosecond domain driven by self‑phase modulation. Moreover, forward SRS provides nanosecond pump pulses at ~1.9 µm for gain‑switched operation of Cr:ZnSe or Cr:ZnS crystals in the spectral range up to ~3 µm.