Slab Laser Research Articles

Quasi-Continuous Wave Pumped Slab Laser Based on Nd:CTGS Crystal

Quasi-Continuous Wave Pumped Slab Laser Based on Nd:CTGS Crystal

Hundred-watts-level Ho:YLF slab laser with good beam quality

We demonstrated a hundred-watts-level and good beam quality Ho:YLF slab laser with a hybrid cavity. When the incident pump power was 263 W, we obtained a maximum output power of 105 W. The slope efficiency with the incident pump power was 52.5%, and the optical-to-optical conversion efficiency was 39.9%. The instability of the maximum output power was measured to be 0.35% in 30 min. With the increase of the output power, the central wavelength of laser shifted from 2051 nm to 2063 nm. The beam quality factors M 2 were measured to be 1.13 in the stable direction and 2.45 in the unstable direction. Hundred-watts-level Ho:YLF slab laser with good beam quality has not been reported yet to the best of our knowledge.

22 kW near-diffraction-limited Yb:YAG slab laser amplifier without adaptive optics correction

22 kW near-diffraction-limited Yb:YAG slab laser amplifier without adaptive optics correction

Above 10 W, 100 kHz-class cavity-dumped Tm:YAP laser at 1.94 μm

We demonstrate a high-repetition-frequency, cavity-dumped Tm:YAP slab laser, producing short nanosecond pulse at 1.94 μm. A thermal-lens-compensated cavity with a dual-end pumping configuration is developed for high-power operation. The achieved maximum Tm laser power is 10.7 W, with a pulse width of 26.4 ns at a frequency of 110 kHz, resulting in a peak power of 3.68 kW. To the best of our knowledge, this represents the highest output power for the cavity-dumped Tm laser. The results provide a robust scheme to develop high-power, high-repetition-frequency diode-pumped 2 μm lasers with a constant sub-50 ns pulse duration, opening avenues for versatile applications including medical treatment, material processing, and nonlinear frequency conversion towards the mid-infrared region.

Cryogenic slab RF discharge CO laser with hybrid waveguide-unstable resonators

Dependences of a cryogenic slab radio-frequency discharge CO laser output power on a distance between mirrors of a hybrid negative-branch waveguide-unstable resonator were experimentally studied. The maximum output power was observed at the resonator length longer than the one calculated by taking into account the mirrors radii of curvature. Optimization of the resonator length made it possible to get the output power increase up to 20%–25%. The results obtained can be used for designing not only slab laser systems with hybrid waveguide-unstable resonators, but also for high-power lasers with full-sized negative-branch unstable ones.

80-W single-frequency Innoslab µs-amplifier at 1319 nm with high efficiency.

A single-frequency quasi-continuous-wave partially end-pumped slab (Innoslab) laser amplifier at 1319 nm was demonstrated. The 3-W single-frequency all-fiber seed laser was amplified to a maximum average power of 80.1 W and the power stability was 0.52% in 10 minutes. The corresponding optical-optical efficiency was 16.1% under absorbed pump power of 478 W. The output pulse width was 131 µs at the repetition of 500 Hz. The beam quality factors of M2 were 1.3 in both the vertical and horizontal directions. To the best of our knowledge, this is the first report on single-frequency Nd:YAG Innoslab amplifier at 1319 nm with such high output power and efficiency.

A Novel PWM Signal-Generation Strategy for Pockels Cell Drivers

A Pockels cell driver (PCD) can be viewed as a high-voltage pulse width generator for controlling the bi-refringence effect of electro-optical crystals. The main features of a PCD include a high repetition rate, fast on and off switching, variable pulse duration, and a true square pulse shape. The most commonly used PCD has a narrow pulse width tuning range, typically within a few microseconds. In this paper, we propose a PCD based on a novel pulse width modulation (PWM) signal-generation strategy that can continuously adjust its pulse width with a minimum step size of 10 ns and no restriction on the maximum width. Therefore, it is easily compatible with both “On-type” and “Off-type” applications of the electro-optic crystal quarter-wave voltage. The experimental results show that the rising and falling times of the proposed PCD are approximately 7.3 ns and 7.8 ns, respectively, with a maximum repetition rate of 1 MHz and a maximum voltage of approximately 2.0 kV. Finally, the functionality of the PCD is demonstrated in a home-built slab laser.

High Power (~10 kW) Yb:YAG Ceramic Slab Laser Operating at 1030 nm

A high power quasi-continuous-wave (QCW) efficiently-cooled ceramic slab laser oscillator is reported. The maximum output power can reach 9.85 kW with the optical-to-optical efficiency of 60% with respect to the absorbed pump power as well as the slope efficiency up to 65.3%. To the best of our knowledge, this is the highest output power for any Yb:YAG ceramic laser oscillator. Beam aberration of the efficiently-cooled Yb:YAG ceramic slab laser is detected by a parallel probe beam along the optical path of laser beam. The peak-to-valley (PV) value of the wavefront distortion is 2.8 μm under full output power. The beam quality factor β is estimated to be about 3.7 times diffraction limit while without additional correction system. A numerical model of temperature field is constructed to analyze the wavefront distortion of the probe beam, and the calculated results are in agreement with the experimental data.

Multilevel synergically controlling wavefront correction of a high-power slab laser system.

We present a multilevel synergically controlling wavefront correction method that can apply in a slab laser system. To fully utilize the response frequency and the stroke of actuators of the single deformable mirror (DM), we design a set of multilevel wavefront correction devices to reduce the root-mean square of wavefront aberration before the DM. As the wavefront of slab geometry solid-state lasers mainly consists of fourth and longitudinally distributed aberration, such as 5th, 9th, and 14th orders of Legendre polynomials. We design a precompensating level of the aberration with a slow-drift mirror, fast-steer mirror, one-dimensional adjustable slab-aberration compensator, and beam-shaping system to reduce these orders of wavefront aberration with low spatial resolution and large stroke. As the controlling bandwidth of different devices is diverse, the coupling oscillation between the precompensating level and adaptive optics (AO) level occurs, then we develop the multilevel synergically control to address the coupling. With the precompensating level, the experimental result shows the residual wavefront aberration of the slab laser is compensated well by the AO level effectively within the compensating capability. We clean up a 9.8kW slab laser system with the beam quality β of far-field focus spots improved from 17.71 to 2.24 times the diffraction limit.

Research on output spot evolution of multi-pass gain Tm:YLF slab laser based on multi-transverse mode competition

In this paper, the multi-transverse mode competition rate equation model of the Tm:YLF slab laser is established based on the cavity structure of multi-pass gain. As the pump power increased, the changing trend of the number of particles in each mode is analyzed. The direction of beam quality change is also mastered, verified by the three-pass gain laser with the evolution of pump power. Due to the limited compression capacity of the x-axial output spot of the three-pass gain laser, the output spot changes significantly under different cavity lengths and output mirror curvatures. By discussing the output spot evolution, it is known that the large curvature output mirror and the appropriate cavity length can optimize the output spot. Finally, under the pump power of 72 W, the four-pass gain laser obtains a laser output of 1.8 W. It’s beam quality is MX2 = 1.77;MY2 = 1.99, the optical–optical conversion efficiency is 2.5 %, and the slope efficiency is 15 %. The beam quality of a three-pass gain laser is MX2 = 2.67; MY2 = 1.70, the optical–optical conversion efficiency is 3.2 %, and the slope efficiency is 11 %. It is verified that the compression of the four-pass gain laser is stronger than that of the three-pass gain laser on the x-axis, laying the foundation for developing a compact multi-pass gain laser.

2.85-kW cryogenic Nd:YAG slab laser operating at 946 nm

A several-kilowatt level laser at 946 nm is demonstrated in a cryogenically cooled diode-pumped Nd:YAG slab system. The oscillator realizes the record of the output power of 2.85 kW in a compact cavity with the homemade cryogenically cooled Nd:YAG crystal slab. The pulse repetition rate and pulse width of the laser are 400 Hz and 200 µs, respectively, and the center wavelength under full power is 946.2 nm with a bandwidth of about 0.5 nm. The absorption linewidth at 808 nm is a little narrowed and blue shifts at the cryogenic temperature, while the cooling temperature decreases from 300 to 77 K. The measured thermal conductivity increases from 10 to 70 W/mˑK, and the thermal expansion coefficient decreases from 7.5*10−6 to 1.5*10−6/K. These results could guide us in simulating the temperature gradient and thermal-induced stress distributions in the crystal slab.

100 W Ho : YLF Slab Laser with Two Crystals End-Pumped by a Tm:YAP Laser

100 W Ho : YLF Slab Laser with Two Crystals End-Pumped by a Tm:YAP Laser

12.7 W intra-cavity pumped Ho:YAG laser with near-diffraction-limited beam quality.

We demonstrated a compact and efficient Ho:YAG slab laser intra-cavity pumped by a Tm:YLF slab laser for the first time. In the Tm:YLF laser operation, the maximum power of 32.1 W with optical-to-optical efficiency of 52.8% was obtained. In the intra-cavity pumped Ho:YAG laser operation, the output power of 12.7 W at 2122 nm was obtained. The beam quality factors M2 in the vertical and horizontal directions were 1.22 and 1.11, respectively. The RMS instability was measured to be lower than 0.1%. To the best of our knowledge, this was the maximum power for the Tm-doped laser intra-cavity pumped Ho-doped laser with near-diffraction-limited beam quality.

341 W Continuous-Wave Dual-End-Pumped Tm:YAP Slab Laser

341 W Continuous-Wave Dual-End-Pumped Tm:YAP Slab Laser

Polarization-controlled switching in a diode-pumped dual-wavelength Yb:YAG slab laser

Polarization-controlled switching in a diode-pumped dual-wavelength Yb:YAG slab laser

500 Hz Joule-level output by sub-nanosecond Zig-Zag slab laser

500 Hz Joule-level output by sub-nanosecond Zig-Zag slab laser

High power ceramic slab laser

High power ceramic slab laser

Simulation and Optimization of Heat Dissipation in Slab Laser Amplifier Based on Microchannel Heat Sink

Simulation and Optimization of Heat Dissipation in Slab Laser Amplifier Based on Microchannel Heat Sink

The Multiparameter Measurement Technique in a Large-Aperture Rectangular Laser Beam Aberration Correction System

Adaptive optics (AO) can effectively improve the beam quality of solid-state slab lasers. However, the aperture of the output beam increases as the output power of the laser increases, resulting in a larger measurement system. Ultimately, a more complex AO system needs to be designed. To meet the requirements of conjugate imaging in an AO system, it is of research significance to coordinate and optimize the system's structural dimensional parameters while enabling the detection of multiple parameters, such as the wave-front and beam quality. In this paper, a multiparameter measurement technique in a large-aperture rectangular laser beam aberration-correction system is proposed. The system layout is optimized with total dimensions of 400 mm × 150 mm × 246 mm (L × W × H). The AO system conforms to the requirements for conjugate detection and can perform wave-front detection, far-field evaluation, and near-field detection of a 160 mm × 120 mm rectangular beam produced from a solid-state slab laser. The findings reveal that the measured PV values of wave-fronts of the measurement system are less than 0.288 μm, the RMS is no more than 0.079 μm, the average far-field beam quality factor is 1.248 times the diffraction limit, and the average near-field beam uniformity is 0.533 at a temperature of 20 °C ± 10 °C; these results satisfy the technical parameters.

Spectral singularities and threshold gain of a slab laser under illumination of a focused Gaussian beam

Spectral singularities of an infinite planar slab containing homogeneous optically active material at the focal plane of a thin lens are investigated. The field distribution of the beam behind the lens is Gaussian that we approximate by a plane wave concentrated near the optical axis at the focal plane of the lens, such that its phase and amplitude are distance-dependent. The consequences of this configuration are explored by determining the threshold gain of the active medium and tuning the resonance frequencies related to spectral singularities. We find that the spectral singularities and the threshold gain, besides that, vary with distance from the center of the Gaussian beam; also they change with the relative aperture of the focusing lens. Numerical studies show that for the central rays of the beam compared to the side rays, the resonances related to the spectral singularities occur at lower wavelengths (higher frequencies) with the highest threshold gain. Also, for the ray at a fixed distance from the center of the beam, increasing the relative aperture of the illuminating system leads to the same results. Numerical results confirm the theoretical findings.