We report on the successful demonstration of a 150 J nanosecond pulsed cryogenic gas cooled, diode-pumped multi-slab Yb:YAG laser operating at 1 Hz. To the best of our knowledge, this is the highest energy ever recorded for a diode-pumped laser system.

We report on a high-power Ho:YAG single-crystal fiber (SCF) laser inband pumped by a high-brightness Tm-fiber laser at 1908 nm. The Ho:YAG SCF grown by the micro-pulling-down technique exhibits a propagation loss of $0.05\pm 0.005~\text{cm}^{-1}$ at $2.09~\unicode[STIX]{x03BC}\text{m}$. A continuous-wave output power of 35.2 W is achieved with a slope efficiency of 42.7%, which is to the best of our knowledge the highest power ever reported from an SCF-based laser in the 2 $\unicode[STIX]{x03BC}\text{m}$ spectral range.

A band-stop angular filter (BSF) based on hump volume Bragg gratings (HVBGs) is proposed. Band-stop filtering in a two-stage amplifier laser system is discussed and simulated. Simulation results show that small-scale self-focusing effects in the laser system can be effectively suppressed with the BSF due to the control of fast nonlinear growth in a specific range of spatial frequencies in the laser beam. Near-field modulation of the output beam from the laser system was decreased from 2.69 to 1.37 by controlling the fast nonlinear growth of spatial frequencies ranging from $0.6~\text{mm}^{-1}$ to $1.2~\text{mm}^{-1}$ with the BSF. In addition, the BSF can be used in a plug-and-play scheme and has potential applications in high-power laser systems.

The output performances of a bidirectional ring amplifier with twin pulses are demonstrated. Compared to the extraction efficiency of 32% for single-pulse injection, the extraction efficiency of stored energy for twin-pulse injection with bidirectional propagation is increased to 60%. The maximum output energies of the twin pulses are 347 mJ and 351 mJ, and the output energy of a single pulse is only 373 mJ under the same amplifier operating conditions. The experimental results show that the bidirectional ring amplifier with twin pulses can achieve a higher extraction efficiency of stored energy at a lower operating fluence, and has potential applications in high-power and high-energy laser facilities.

We report on the generation of a mid-infrared (mid-IR) frequency comb with a maximum average output power of 250 mW and tunability in the 2.7–4.0 μm region. The approach is based on a single-stage difference frequency generation (DFG) starting from a compact Yb-doped fiber laser system. The repetition rate of the near-infrared (NIR) comb is locked at 75 MHz. The phase noise of the repetition rate in the offset-free mid-IR comb system is measured and analyzed. Except for the intrinsic of NIR comb, environmental noise at low frequency and quantum noise at high frequency from the amplifier chain and nonlinear spectral broadening are the main noise sources of broadening the linewidth of comb teeth, which limits the precision of mid-IR dual-comb spectroscopy.

We report a 2 kW all-fiberized Raman fiber amplifier with efficient brightness enhancement based on the graded-index fiber. The maximum power output reaches up to 2.034 kW centered at 1130 nm, with a conversion efficiency of 79.35% with respect to the injected pump power. To the best of our knowledge, this is the highest conversion efficiency obtained for any Raman laser system using graded-index fiber. An optimized fiber combiner adopting graded-index fiber as the pigtail fiber was fabricated, enabling the preservation of the seeding brightness in the core-pumped Raman fiber amplifier, and further enhancing the ultimate brightness of the output laser after amplification. At the maximum power output, the beam quality parameter M2 is 2.8, corresponding to a signal-to-pump brightness enhancement factor of 11.2. As far as we know, we obtain the highest brightness enhancement among Raman fiber lasers of over 100 W, and the best beam quality for graded-index Raman fiber lasers of over 150 W.

This study develops a Yb:KGW dual-crystal based regenerative amplifier. The thermal lensing and gain-narrowing effects are compensated by the dual-crystal configuration. Sub-nanojoule pulses are amplified to 1.5 mJ with 9 nm spectral bandwidth and 1 kHz repetition rate using chirped pulse amplification technology. Consequently, 1.2 mJ pulses with a pulse duration of 227 fs are obtained after compression. Thanks to the cavity design, the output laser was a near diffraction limited beam with M2 around 1.1. The amplifier has the potential to boost energy above 2 mJ after compression and act as a front end for a future kilohertz terawatt-class diode-pumped Yb:KGW laser system.

We report on the study of single-mode fiber-laser-pumped mode-locked Yb:CALYO lasers via using a passive saturable absorber and Kerr-lens mode-locking technique, respectively. Up to 3.1-W average power with 103-fs pulse duration is obtained from the passive mode-locking, and down to 36-fs pulse duration with more than 2-W average power is achieved by the pure Kerr-lens mode-locking, which is to the best of our knowledge, the highest average power from a reported sub-40-fs Yb-based solid-state oscillator.

We report on a new scheme for efficient continuous-wave (CW) mid-infrared generation using difference frequency generation (DFG) inside a periodically poled lithium niobate (PPLN)-based optical parametric oscillator (OPO). The pump sources were two CW fiber lasers fixed at 1018 nm and 1080 nm. One worked as the assisted laser to build parametric oscillation and generate an oscillating signal beam while the other worked at low power (${\leqslant}3~\text{W}$) to induce DFG between it and the signal beam. The PPLN temperature was appropriately adjusted to enable OPO and DFG to synchronously meet phase-matching conditions. Finally, both low-power 1018 nm and 1080 nm pump beams were successfully converted to $3.1~\unicode[STIX]{x03BC}\text{m}$ and $3.7~\unicode[STIX]{x03BC}\text{m}$ idler beams, respectively. The conversion efficiencies of the 1018 nm and 1080 nm pumped DFG reached 20% and 15%, respectively, while their slope efficiencies reached 19.6% and 15%. All these data were comparable to the OPOs pumped by themselves and never realized before in traditional CW DFG schemes. The results reveal that high-efficiency frequency down-conversion can be achieved with a low-power near-infrared pump source.