ABSTRACT
We report on the successful amplification of 10 ns pulses to 10 J energy at 10 Hz in a DiPOLE laser amplifier using crystalline Yb:YAG/Cr:YAG composite slabs manufactured using adhesive-free bonding (AFB) technology. We demonstrate that bonded slabs are suitable for operation in high energy cryogenic laser amplifiers. We also report on frequency doubling of the beam amplified in the bonded slabs. When the pulse energy of the output infrared beam is set to 5 J, a pulse energy of 3.9 J is achieved in the green (corresponding to 78% conversion efficiency). Results demonstrate that AFB technology is suitable for producing large-sized gain material slabs and can overcome current limitations in the manufacture of large-aperture gain material pieces. We believe this work will facilitate energy scaling of high energy lasers where aperture scaling of optical elements is not achievable via conventional manufacturing techniques.
ABSTRACT
In this paper, we present a model to predict thermal stress-induced birefringence in high energy, high repetition rate diode-pumped Yb:YAG lasers. The model calculates thermal depolarisation as a function of gain medium geometry, pump power, cooling parameters, and input polarisation state. We show that model predictions are in good agreement with experimental observations carried out on a DiPOLE 100 J, 10 Hz laser amplifier. We show that single-pass depolarisation strongly depends on input polarisation state and pumping parameters. In the absence of any depolarisation compensation scheme, depolarisation varies over a range between 5% and 40%. The strong dependence of thermal stress-induced depolarisation on input polarisation indicates that, in the case of multipass amplifiers, the use of waveplates after every pass can reduce depolarisation losses significantly. We expect that this study will assist in the design and optimisation of Yb:YAG lasers.
ABSTRACT
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.
ABSTRACT
The Diode Pumped Optical Laser for Experiments (DiPOLE) project at the Central Laser Facility aims to develop a scalable, efficient high pulse energy diode pumped laser amplifier system based on cryogenic gas cooled, multi-slab ceramic Yb:YAG technology. We present recent results obtained from a scaled down prototype laser system designed for operation at 10 Hz pulse repetition rate. At 140 K, the system generated 10.8 J of energy in a 10 ns pulse at 1029.5 nm when pumped by 48 J of diode energy at 940 nm, corresponding to an optical to optical conversion efficiency of 22.5%. To our knowledge, this represents the highest pulse energy obtained from a cryo cooled Yb laser to date and the highest efficiency achieved by a multi-Joule diode pumped solid state laser system. Additionally, we demonstrated shot-to-shot energy stability of 0.85% rms for the system operated at 7 J, 10 Hz during several runs lasting up to 6 hours, with more than 50 hours in total. We also demonstrated pulse shaping capability and report on beam, wavefront and focal spot quality.
ABSTRACT
Temperature dependent absorption and emission cross-sections of 5 at% Yb(3+) doped yttrium lanthanum oxide (Yb:YLO) ceramic between 80K and 300 K are presented. In addition, we report on the first demonstration of ns pulse amplification in Yb:YLO ceramic. A pulse energy of 102 mJ was extracted from a multi-pass amplifier setup. The amplification bandwidth at room temperature confirms the potential of Yb:YLO ceramic for broad bandwidth amplification at cryogenic temperatures.
ABSTRACT
We report on the first demonstration of a diode-pumped, gas cooled, cryogenic multislab Yb:YAG amplifier. The performance was characterized over a temperature range from 88 to 175 K. A maximum small-signal single-pass longitudinal gain of 11.0 was measured at 88 K. When amplifying nanosecond pulses, recorded output energies were 10.1 J at 1 Hz in a four-pass extraction geometry and 6.4 J at 10 Hz in a three-pass setup, corresponding to optical to optical conversion efficiencies of 21% and 16%, respectively. To our knowledge, this represents the highest pulse energy so far obtained from a cryo-cooled Yb-laser and the highest efficiency from a multijoule diode pumped solid-state laser system.
ABSTRACT
Diffusion bonded (DB) walk-off compensated KTP crystals offer an alternative nonlinear medium for efficient 1 to 2 microm conversion within optical parametric oscillators (OPOs) at low pulse energies. Spatial variations in optical absorption and transmission values measured at 2 mum are reported for two DB-KTP crystals. Finally, a comparison is made between the conversion efficiency obtained from a degenerate 1 microm pumped OPO using a single 20 mm KTP crystal and an equivalent length DB-KTP crystal consisting of two bonded 10 mm crystals.
