Low-noise, 2-W average power, 112-fs Kerr-lens mode-locked Ho:CALGO laser at 2.1 µm

High average output power, dual-wavelength synchronously self-mode-locked Ho:LLF laser operating at 2068.5 and 2069.2 nm

A dual-wavelength synchronously self-mode-locked Ho:LLF laser operating at 2068.5 and 2069.2 nm was demonstrated. The maximum average output power was as high as 2.6 W with a pulse repetition frequency of 3.03 GHz. Meanwhile, the output power ratio of the dual-wavelength lasers can be effectively controlled by varying the incident pump power. To the best of our knowledge, this is the first dual-wavelength synchronously self-mode-locked Ho-doped fluoride solid state laser; moreover, our current experimental results represent the highest average output power from a GHz self-mode-locked oscillator in the 2 µm wave band.

High-power, gigahertz repetition frequency self-mode-locked Ho:GdVO4 laser resonantly pumped by a Tm-doped fiber laser

A self-mode-locked Ho:GdVO4 laser with the GHz pulse repetition frequency oscillation near 2.06 µm was demonstrated for the first time to our knowledge. The output performances of the self-mode-locked Ho:GdVO4 laser were investigated for a few output coupler transmittances at the pulse repetition frequency of 1.89 GHz. At the incident pump power of 8.12 W, the maximum average output power was as high as 2.28 W, corresponding to the slope efficiency and optical-to-optical efficiency of 36.3% and 28.1%, respectively. This is the maximum average output for the 2 µm self-mode-locked solid-state laser with a GHz pulse repetition frequency. This work provides a new way for generating an efficient and a high-power ultrafast pulse laser with a GHz repetition frequency in the 2 µm wave band.

GHz repetition rate, sub-100-fs Ho:CALGO laser at 2.1 µm with watt-level average power

We report on a GHz fundamental repetition rate Kerr-lens mode-locked Ho:CALGO laser emitting at 2.1 µm. The laser employs a ring cavity to increase the fundamental repetition rate to 1.179 GHz and can be made to oscillate in both directions stably with nearly identical performance: for the counterclockwise oscillation, it generates 93-fs pulses at 1.68 W of average power, whereas 92 fs and 1.69 W were measured for the clockwise operation. Our current results represent the highest average power from a 2-µm GHz oscillator and, to our knowledge, the first sub-100-fs pulse duration from a Ho-based oscillator.

Sub-60-fs mode-locked Tm,Ho:CaYLuAlO4 laser at 2.05 µm

Tm,Ho:CaYLuAlO4 (Tm,Ho:CALYLO) crystal has wide emission spectra both for π-polarization and σ-polarization, showing significant potential for the generation of ultrashort pulses. Here, a widely tunable and passively mode-locked laser operation based on Tm,Ho:CALYLO crystal under two polarizations was demonstrated for what we believe to be the first time ever. For π-polarization, a maximum output power of 1.52 W and a tuning range of 255.3 nm were achieved in the continuous wave (CW) regime. In the mode-locked regime, a pulse duration of 68 fs and an average output power of 228 mW were achieved upon GaSb-based semiconductor saturable absorber mirror (SESAM). As for σ-polarization, a broader tuning range of 267.1 nm was realized, leading to the shorter pulse duration of 58 fs at 79.7 MHz repetition rate.

Compact, ultrastable, high repetition-rate 2 μm and 3 μm fiber laser for seeding mid-IR OPCPA

We report a compact and reliable ultrafast fiber laser system optimized for seeding a high energy, 2 μm pumped, 3 μm wavelength optical parametric chirped pulse amplification to drive soft X-ray high harmonics. The system delivers 100 MHz narrowband 2 μm pulses with >1 nJ energy, synchronized with ultra-broadband optical pulses with a ∼1 μm FWHM spectrum centered at 3 μm with 39 pJ pulse energy. The 2 μm and 3 μm pulses are derived from a single 1.5 μm fiber oscillator, fully fiber integrated with free-space downconversion for the 3 μm. The system operates hands-off with power instabilities <0.2% over extended periods of time.

Mode-locking of a Tm,Ho:CALYGO laser delivering 50 fs pulses at 2.08 µm

We study the polarization-dependent laser performance of a novel, to the best of our knowledge, "mixed" Tm,Ho:CaYGdAlO4 crystal in the continuous-wave (CW) and mode-locked regimes. Both in terms of the CW tunability range (261 nm) and the minimum pulse duration (50 fs at 2078 nm, spectral width of 95 nm) in the mode-locked regime, σ-polarization is superior. With extended inhomogeneous spectral broadening due to structural and compositional disorder, Tm,Ho:CaYGdAlO4 is promising for few-optical-cycle pulse generation around 2 µm.