Effect of amplified spontaneous emission and parasitic oscillations on the performance of cryogenically-cooled slab amplifiers

We present benchmarking of the home-made MATLAB model with the experimental data obtained for the 10 J/10 Hz cryogenically cooled multi-slab laser systems being developed in the Rutherford Appleton Laboratory, STFC, UK. The laser head of each system consists of four, 5 mm thick slabs separated by 2 mm gaps. Each slab is composed of 35 mm diameter Yb:YAG active material surrounded by 10 mm thick absorptive cladding. The slabs are pumped from both sides by diode arrays which in total deliver up to 40 kW of pump power in 1 ms pulses with a central wavelength of 940 nm, bandwidth 6 nm and pump spot 20 mm x 20 mm. The laser head has been modeled to predict gain in the slabs and the amplification of the seed beam for the temperatures of operation ranging from 100 K to 180 K. Output energy for different pump pulse durations has been calculated. It was determined that the maximum output energy obtained after 6 passes for the amplifier operating at the temperature of 120K and repetition rate 1 Hz was 9 J for the seed energy of 20 mJ. For higher temperature of 160 K the output energy was 8 J. The corresponding maximum single pass gain in the amplifier head was 8 for 120 K and 4 for 160 K. Results of the simulations are in a very good agreement with the measured data presented in [1].

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“…For the whole simulation process the energy flow in the system is tracked. Detailed description of the code was given in [7,8].…”

Section: Description Of the Modelmentioning

confidence: 99%

Experimental benchmarking of the code for Yb:YAG multi-slab gas-cooled laser system operating at cryogenic temperatures

Sawicka-Chyla

Slezák²,

Divoký

et al. 2015

SPIE Proceedings

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“…The probability of reflection at the edge is calculated from the Fresnel equations for the incident angle of the ray. If photons are reflected back, they pass through the absorptive layer again and, if they are not absorbed, they propagate back to the gain medium and decrease the stored energy [6] .…”

Section: Energetics Modelingmentioning

confidence: 99%

“…For our kJ-class HiLASE laser, we have chosen to model an amplifier with the characteristics derived from the previous ASE and thermal study [6,7] , i.e., eight 1 cm thick Yb at 1030 nm) around the edge of each slab was also included to further suppress ASE and prevent unwanted parasitic oscillations. The edges of the cladding were modeled as roughened surfaces which scatter rays.…”

Section: Amplifier Concept and Simulationsmentioning

confidence: 99%

“…Recent studies have shown that diode-pumped solid-state lasers (DPSSLs) are the most promising laser systems to reach the requirements for such a driver, namely multi-100 kJ energy of ns pulses, multiHz repetition rates and high wall-plug efficiencies between 10% and 15% [3,4] . The HiLASE team is developing an Yb 3+ :YAG gain medium based concept for a 100 J/10 Hz DPSSL amplifier that could potentially be scaled to the kJ regime [5][6][7] . While there are several projects around the world that are trying to achieve the same goal [8][9][10][11] , HiLASE is expected to be completed in May 2015 and it will be the world's highest pulse energy short pulse (2-10 ns) DPSSL at 100 J and 1-10 Hz.…”

Section: Introductionmentioning

confidence: 99%

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Design of a kJ-class HiLASE laser as a driver for inertial fusion energy

Lucianetti

Sawicka

Slezák

et al. 2014

High Pow Laser Sci Eng

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We present the results of performance modeling of a diode-pumped solid-state HiLASE laser designed for use in inertial fusion energy power plants. The main amplifier concept is based on a He-gas-cooled multi-slab architecture similar to that employed in Mercury laser system. Our modeling quantifies the reduction of thermally induced phase aberrations and average depolarization in Yb 3+ :YAG slabs by a combination of helium cryogenic cooling and properly designed (doping/width) cladding materials.

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“…The threshold of the parasitic oscillation and the reflectivity of ASE are determined by R, which is a function of the refractive index match of the laser glass, the polymer, and the cladding glass [5,12] . Therefore, R must be sufficiently low (e.g., R < 0.1%) when developing the edge cladding [13] . Refractive indices of the laser glass and the cladding glass are close and steady, and the polymer refractive index is possible to be adjusted by adding or subtracting functional groups with different polarizabilities.…”

mentioning

confidence: 99%

Effect of temperature on refractive index match of laser glass edge cladding

Hu¹,

Meng²,

Chen³

et al. 2014

中国光学快报

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An Nd:glass disc requires an edge cladding to absorb the amplified spontaneous emission. The absorption is determined by reflections (R) from disc edges. R is primarily induced by the refractive index (n) mismatch. Thus, the temperature at the cladding interface increases due to absorption, and leads to the variation of n. In order to investigate the effect of temperature on the refractive index match, temperature coefficients (dn/dT) of the laser glass, adhesive polymer, and cladding glass are measured. The effect of temperature on the refractive index match is discussed. Results show that the indices match below 40 °C.

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Effect of amplified spontaneous emission and parasitic oscillations on the performance of cryogenically-cooled slab amplifiers

Cited by 13 publications

References 18 publications

Experimental benchmarking of the code for Yb:YAG multi-slab gas-cooled laser system operating at cryogenic temperatures

Experimental benchmarking of the code for Yb:YAG multi-slab gas-cooled laser system operating at cryogenic temperatures

Design of a kJ-class HiLASE laser as a driver for inertial fusion energy

Effect of temperature on refractive index match of laser glass edge cladding

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