Antonio Lucianetti

Modeling of amplified spontaneous emission, heat deposition, and energy extraction in cryogenically cooled multislab Yb 3+ :YAG laser amplifier for the HiLASE Project

A three-dimensional ray-tracing code for determination of amplified spontaneous emission in a multislab laser amplifier is presented. In addition to energy stored in the amplifier, the code also calculates the heat distribution and the amplification of the signal beam. For cryogenically cooled multislab amplifiers with Yb3+:YAG and absorptive Cr4+:YAG cladding, energy storage efficiency greater than 52% and small signal gain of 22  m−1 were obtained. The pump energy converted to heat was found to be 11% in the active volume and 50% in the Cr4+:YAG cladding.

100 J-level nanosecond pulsed diode pumped solid state laser

We report on the successful demonstration of a 100 J-level, diode pumped solid state laser based on cryogenic gas cooled, multi-slab ceramic Yb:YAG amplifier technology. When operated at 175 K, the system delivered a pulse energy of 107 J at a 1 Hz repetition rate and 10 ns pulse duration, pumped by 506 J of diode energy at 940 nm, corresponding to an optical-to-optical efficiency of 21%. To the best of our knowledge, this represents the highest energy obtained from a nanosecond pulsed diode pumped solid state laser. This demonstration confirms the energy scalability of the diode pumped optical laser for experiments laser architecture.

High-Contrast, High-Intensity Petawatt-Class Laser and Applications

A high-contrast high-intensity petawatt-class Ti:sapphire chirped-pulse amplification laser has been developed for research on high field science. A saturable absorber and a low-gain optical parametric chirped-pulse amplification preamplifier in the front-end have improved the temporal contrast in the system to ∼

Design of high-energy-class cryogenically cooled Yb3+∶YAG multislab laser system with low wavefront distortion

2 \times 10^{12}

Optimization of Wavefront Distortions and Thermal-Stress Induced Birefringence in a Cryogenically-Cooled Multislab Laser Amplifier

on the subnanosecond time scale at the ∼70 TW power level. In addition to the high-contrast broadband high-energy output from the final amplifier has been achieved with a flat-top spatial profile with a filling factor of ∼70%. This is the result of pump beam spatial profile homogenization with diffractive optical elements. The system produces the uncompressed output pulse energy of 29 J, indicating the capability for reaching a peak power of ∼600 TW. We discuss in detail the design, performance, and characterization of the laser including output power, pulse duration, and spatiotemporal beam quality. We also describe the on-going upgrade of the laser system and some applications for the laser in relativistic dominated laser–matter interactions.

Wavelength dependence of magneto-optic properties of terbium gallium garnet ceramics

Abstract. Detailed modeling results of 100 J class laser systems with respect to the output energy, beam propagation, nonlinear phase accumulation, wavefront aberrations, and adaptive optics performance obtained in MIRÓ and MATLAB codes are presented here. The laser system is based on a cryogenically cooled Yb3+∶YAG multislab amplifier with two identical amplifier heads and operates at 10 Hz repetition rate with an average power above 1 kW.

Spectroscopic characterization of various Yb3+ doped laser materials at cryogenic temperatures for the development of high energy class diode pumped solid state lasers

The optimization of the Yb:YAG gain medium and absorbing clad parameters was investigated for efficient heat removal in cryogenically-cooled multislab amplifiers operating in the kilowatt average power range (100 J/10 Hz). The 3-D distributions of temperature, stress, strain, and birefringence were calculated by a finite element analysis. Based on these data, the space-resolved optical path difference and depolarization losses were determined considering eight slabs, two laser heads, and four passes. We have found that a combination of properly designed (doping/width) index matching material and helium cryogenic cooling leads to a quasi-constant transverse temperature distribution in the pump area and a very small axial thermal gradient in the slab. It is shown that the resulting thermally induced phase aberrations, stresses, and average depolarization are rendered insignificant.

Kilowatt average power 100 J-level diode pumped solid state laser

The wavelength dependence of magneto-optic properties of TGG ceramics, including the Verdet constant, has been investigated experimentally. The previously obtained Verdet constant of 36.4 rad/Tm for 1064 nm wavelength and 139.6 rad/Tm for 633 nm are in good agreement with presented white light measurements . The comparison with previously reported Verdet constant and absorption coefficient values for TGG single crystal has shown very similar results. These results lead to the conclusion that TGG ceramics is a very good alternative to TGG single crystal and is a powerful approach for realizing large-aperture optical isolators which are required in high-average-power laser systems.

Design and optimization of an adaptive optics system for a high-average-power multi-slab laser (HiLASE)

Precise values of absorption, emission and gain cross-sections of Yb:YAG, Yb:LuAG, Yb:CaF2 and Yb:FP15-glass at cryogenic temperatures are presented. To obtain the emission cross-sections two theoretical approaches were used. The first is the McCumber or reciprocity method (RM) which is based on the absorption spectra. The second is the Fuchtbauer-Ladenburg (FL) method using fluorescence spectra. From the results of cross-sections one can expect significant impact on laser performance on these materials especially in the case of high energy class diode pumped solid state lasers.

Thermal effects in the Input Optics of the Enhanced Laser Interferometer Gravitational-Wave Observatory interferometers.

We report efficient and stable operation of the first multi-joule diode pumped solid state laser delivering 1 kW average power in 105 J, 10 ns pulses at 10 Hz, confirming the power scalability of multi-slab cryogenic gas-cooled amplifier technology.