Yttrium Aluminum Garnet (YAG) is a promising material for solid state fiber lasers. The cladding surrounding the YAG core must have a tightly controlled refractive index, high thermal conductivity, and be fully dense. Ca3Ga2Ge3O12 (CGG) is a potential cladding material that meets these criteria, and has a low melting-temperature, allowing for unique processing methods. This presentation will discuss application of a dense CGG cladding onto a YAG fiber core using a Laser Heated Pedestal Growth (LHPG) apparatus. In-situ melt/solidification of the CGG in the LHPG will be shown, as well as characterization of cladded fibers via SEM, EDS, and TEM.

Rare-earth-doped fibers with single-crystal cores have the potential for 10x higher TMI threshold than their glass counterparts and are a promising candidate for use as gain media in high-power laser systems. Their utility has been limited by parasitic optical losses and difficulty in fabrication. This paper explores methods of fabrication of the fibers including core growth via LHPG and application of cladding materials.

Single-cavity dual-comb lasers are emerging as new light sources benefiting many applications. Here we demonstrate two new operation regimes for these lasers: a 250-MHz repetition rate 1-ps pulse duration laser, and a 1-GHz 80-fs laser. Each source delivers more than 2 W of average power per comb. Compared to our earlier 80-MHz laser which was limited to 500 Hz, both new lasers can achieve up to 25 kHz repetition rate difference without aliasing. We study the suitability of these lasers for comb line resolved measurements and we show excellent coherence between the pulse trains which enables long-term coherent averaging by computational comb line tracking.

Pump-probe lasers for FELs must provide stable pulse energy, timing, and beam position. Here, we show active stabilization of beam pointing fluctuations using a combination of classic control, artificial intelligence, and machine learning techniques. As our laser system operates in 10 Hz burst mode, fast feedback is not possible. Therefore, we have to utilize the available information as efficiently as possible. Beam pointing fluctuations of laser beams can be described by 4 parameters – as the actuators (motorized mirrors) are not orthogonal we need a model to calculate the required actuator movements. As effects such as motor acceleration are not easy to capture in a physical model, we use an automated data-driven approach. The measurement of the beam position is noisy, so we use a Kalman-Filter, which also integrates our feedback actions to smooth the output. Finally, we use an integrating controller to control the beam. The final transport of the beam to the pump-probe experiment introduces additional drifts, but during user operation, the beam position at the interaction point cannot be measured. We, therefore, measure correlated properties such as temperature, humidity, and air pressure and trained a machine learning model to predict its location. Integrating this model in a feed-forward loop could improve the RMS error of the beam position by 63% in the x-axis and 8% in the y-axis.

A femtosecond diode-pumped mode-locked laser operating at 8.2 MHz repetition rate has been demonstrated. The cavity was extended with a White cell configuration consisting of three concave mirrors of the same radius of curvature. The laser produced 126 fs long pulses with a 10% output coupler. The corresponding pulse energy was 52 nJ and peak power reached 416 kW. To the best of our knowledge, this is the lowest repetition rate Yb-ion laser operating in the 100 fs level regime.

High power amplification of a 2090 nm radially polarized laser beam has been demonstrated using a double-pass Ho:YAG thin-slab crystal, generating up to 33.7 W of output power for a 13.2 W radially polarized seed laser. The amplifier crystal was end-pumped with a 95 W single-mode 1907 nm thulium fiber laser, tailored for suitable overlap with the radially polarized beam. By compensation of depolarizing effects such as thermally-induced stress birefringence and the Gouy phase shift, the degradation of the radially polarized beam is minimized, with the chosen amplifier architecture being readily applicable to much higher seed and pump powers.

The development of a 20.6 W radially polarized Ho:YAG laser is reported, which has been actively Q-switched in order to generate 0.52 mJ pulses with a 210 ns full-width half-maximum duration. By utilizing a laser-written spatially-variant birefringent waveplate (S-waveplate) with ultra-low scattering losses inside the cavity, the linearly polarized beam exiting the acousto-optic modulator is transformed into radial polarization with very high conversion efficiency. The excellent radial polarization purity (49:1) and beam quality (M2 of 2.14) highlight this approach as a very suitable platform for high power operation, assisted by the large damage threshold and customizability of the S-waveplate.

We report on developing two flashlamp-pumped electro-optically Q-switched Cr:Er:YSGG lasers with the Q-switch based on La3Ga5SiO14 crystal. The “short” laser cavity was optimized for applications requiring high peak power. In this cavity, the 300 mJ output energy in 15 ns pulses at 3Hz repetition rate was demonstrated under pump energy below 52 J. However, several applications, such as Fe:ZnSe pumping in a gain-switched regime, requiring longer (~ 100 ns ) pump pulse duration. We developed a 2.9 m long laser cavity capable of delivering 190 mJ of output energy in 85 ns pulses for these applications.

The increasing use of short – and ultrashort pulsed lasers in industrial applications leads to a demand for high power industrial-grade lasers covering a large range of pulsed laser parameters. We will present a comprehensive overview of our latest pulsed laser results based on different laser building blocks such as seed lasers, fiber amplifiers, rod and slab amplifiers, thin disk amplifiers and combinations thereof. Along with the technical insights we will give an outlook on the next development steps to further scale these parameters.

We present an air-cooled unstable cavity Nd:YAG/Cr4+:YAG ceramic microchip laser generating pulses with an energy of 22.54 mJ, a duration of 313.5 ps, and a beam quality M2 of 5.79 at 100 Hz, corresponding a record peak power of 71.9 MW and a record brightness of 189.5 TW/(sr∙cm2). However, the small but high intensity center peak of Bessel-like far-field beam can increase the brightness effectively up to 884 TW/(sr∙cm2) with a long effective Rayleigh range. No significant degradation of laser characteristics was confirmed during power scaling in contrast to common flat-flat resonators, promising further brightness scale-up without amplifier.

Laser amplifiers producing high energy (multi-J) nanosecond pulses at high repetition rate (multi-Hz) are required for a wide range of commercial and scientific applications. The DiPOLE concept, developed at the STFC Central Laser Facility (UK), consists in scalable, high-energy DPSSL amplifiers based on cryogenically-cooled, multi-slab ceramic Yb:YAG. In this work we discuss the most recent developments aimed at scaling the pulse repetition of new generation DiPOLE lasers from 10 Hz to 100 Hz. We present the design and current status of a 10 J, 100 Hz DiPOLE laser. We will discuss thermal management approaches adopted for this system.

Quantel USA has leveraged decades of experience designing high power pulsed solid state lasers for military and industrial applications to advance the SWaP-C in the 100mJ laser class. The ShrikeTM laser has increased power output per unit volume by more than 2x compared to the closest competitor, at greater than 7mW/cm3. Diode pumping ensures maximum uptime for use in high-rate manufacturing that require continuous emission, with months or years between service cycles. This architecture is also deployed into military environments, and has the requisite environmental ruggedization and hardening, which high reliability industrial applications can benefit from.

High-energy, diode-pumped, solid-state laser technology, such as DiPOLE, is key for a wide range of applications including the realisation of petawatt-class chirped pulse amplification systems operating at an unprecedented 10Hz repetition rate. In particular, optimisation of the non-linear frequency conversion process from 1030nm to 515nm is required for pumping titanium sapphire, a common gain material. This process is polarisation-sensitive and suffers from losses due to depolarisation, an effect that causes the polarisation state of the beam to vary across the beam aperture. A summary of the methods used for measuring and controlling polarisation in DiPOLE systems will be presented.

Current work reports comparative laser characterization of Cr:ZnS/Se polycrystalline gain media in non-selective Fabry-Perot and twisted mode cavities. It was demonstrated that the spectral output of lasers based on polycrystalline Cr:ZnS/Se in non-selective Fabry-Perot cavities is broadened to ~20-50 nm due to spatial hole burning in the gain elements. Mitigating the spatial hole burning in the same cavities via “mode twisting” results in narrow-line oscillation with linewidth narrowing to ~80-90 pm. Switching between broadened and narrow line oscillations was demonstrated by adjusting the orientation of intracavity waveplates with respect to the Brewster facilitated polarization.

We present a new flexible 3D ray-tracing code, SoLEnA (Simulation of Light Emission and Amplification) to describe amplification, ASE, and PO in a solid-state amplifier. The code simulates the propagation of pump and witness beams, the pumping of the amplifier material, the polarisation-dependent fluorescence and stimulated emission, arbitrary geometries with multiple materials, and the partial reflection of light at the material interfaces. The polarisation dependence of the material parameters allows high fidelity simulations of realistic Ti:sa solid state amplifiers. We use the code to investigate various geometries of high power, high repetition rate laser amplifiers.