Slab Amplifier Research Articles

Multi-watt CW output from a double-pass diode side-pumped Nd:YVO 4 amplifier with a Rh:BaTiO 3 phase conjugator

We demonstrate a 7.8 W high beam quality continuous-wave output of a double-pass Nd:YVO 4 slab amplifier with a photorefractive ring phase conjugate mirror. Optical extraction efficiency of 33% was obtained. Build-up time of the output of the amplifier was 10 s. Standard variance of the output power fluctuation was 2.6%.

Efficient high-gain laser amplification from a low-gain amplifier by use of self-imaging multipass geometry

We characterize a self-imaging multipass amplifier scheme that provides both high extraction efficiency and overall gain. A diode-pumped slab amplifier with a single-pass small-signal gain of 2.5 is used in a 16-pass mode to amplify an input pulse from 50 muJ to 50 mJ, extracting approximately 22% of the stored energy. A stimulated Brillouin-scattering phase-conjugate mirror provides isolation from amplified spontaneous emission, prevents gain depletion, and also ensures good beam quality. The system can be operated from 10 Hz to in excess of 450 Hz, with modest changes in the beam quality and energy. The scheme has the potential to be scaled to higher-energy and higher-power systems.

Conceptual Design of Laser-Diode-Pumped Water-Cooled Nd:Glass Slab Laser Driver for Inertial Fusion Energy.

We have proposed and designed a laser-diode-pumped laser driver for inertial fusion energy (IFE) which consists of water-cooled zig-zag path Nd: glass (HAP-4) slab amplifiers. A driver module was designed under the several operational constraints and has 10 kJ total output energy at 351 nm and operates at 12 Hz with 9-12% overall efficiency. The laser driver producing 4 MJ blue output for IFE will consist of 400 modules

A tunable self-pumped phase-conjugate laser using Ti:sapphire slab amplifiers

We present the first experimental demonstration of a compact self-pumped phase-conjugate laser using transversely laser-pumped Ti 3+:sapphire slab amplifiers as the gain media. The tunable system produces TEM 00 output in a single longitudinal mode, exhibits greater than 300 times phase-conjugate energy reflectivity and a low input energy threshold of ∼10 μJ. By the addition of a partial reflector a self-starting adaptive laser is constructed that operates with a narrowband output and its phase-conjugate nature is demonstrated by correction of intracavity phase distortions.

Conceptual design of a laser-diode-pumped Nd:glass slab laser driver for inertial fusion energy

We have proposed and designed a laser-diode-pumped laser driver for inertial fusion energy (IFE) which consists of water-cooled zig-zag path Nd:glass slab amplifiers. A driver module was designed under the several operational constraints and has 10 kJ total output energy at 351 nm and operates at 12 Hz with 10.4% overall efficiency. The laser driver producing 4 MJ blue output for IFE will consist of 400 modules.

Demonstration of high energy-extraction efficiency in a novel laser-diode pumped eight-pass Nd:YAG zig–zag slab amplifier

A novel laser-diode pumped eight-pass Nd:YAG zig–zag slab amplifier architecture was developed with the aim of achieving high energy-extraction efficiency. High energy-extraction efficiency of up to 71% for the laser mode volume has been achieved in this amplifier operating at an initial small signal gain of 3.25. The compensation of thermal birefringence in this amplifier was successfully performed.

Flashlamp-Pumped ND:Glass Amplifiers for the National Ignition Facility

This paper describes the design and performance of flashlamp-pumped, Nd:glass. Brewster-angle slab amplifiers intended to be deployed in the National Ignition Facility (NIF). To verify performance, we tested a full-size, three-slab-long, NIF prototype amplifier, which we believe to be the largest flashlamp-pumped Nd:glass amplifier ever assembled. Like the NIF amplifier design, this prototype amplifier had eight 40-cm-square apertures combined in a four-aperture-high by two-aperture-wide matrix. Specially-shaped reflectors, anti-reflective coatings on the blastshields, and preionized flashlamps were used to increase storage efficiency. Cooling gas was flowed over the flashlamps to remove waste pump heat and to accelerate thermal wavefront recovery.The protoytpe gain results are consistent with model predictions and provide high confidence in the final engineering design of the NIF amplifiers. Although the dimensions, internal positions, and shapes of the components in the NIF amplifiers will be slightly different from the prototype, these differences are small and should produce only slight differences in amplifier performance.

Nonlinear thermal and stress effects and scaling behavior of YAG slab amplifiers

Yttrium aluminum garnet (YAG) has thermal and mechanical properties that vary strongly with temperature. In the paper, we extend previously reported rod amplifier nonlinear average power scaling relationships to slab amplifiers. As found previously with rod amplifiers, we show that, at room temperature and below, temperature profiles obtained are nonquadratic and that the magnitude of the stresses are seriously underestimated if variations in YAG properties with temperature are ignored. Our results are applied to Nd:YAG and Yb:YAG lasers operating with coolant temperatures at room temperature and 77 K. As found previously with rod lasers, significant increases in average power can be obtained by operating Nd:YAG and Yb:YAG lasers at 77 K. In addition, we compare the nonlinear average power scaling behavior of rod and slab amplifiers using both linear and nonlinear approaches.

Design and testing of a large-aperture, high-gain, Brewster’s angle zigzag Nd:glass slab amplifier

At the University of Rochester we have constructed and tested a large-aperture, (1.0 x 6.5 cm), high-gain (8) Brewster 's angle zigzag Nd:glass amplifier with a repetition rate of 2 Hz. This amplifier has a gain uniformity of +/-3 % and a maximum stress-induced depolarization <2.5 %.

Frequency sweeping of radiation in a system with a monolithic laser and a pulsed slab amplifier

Theoretical and experimental investigations were made of frequency sweeping in a system formed by a highly stable cw master oscillator and a multipass pulsed slab amplifier. It is shown that in a four-pass small-signal amplification system the chirp of the amplified radiation does not exceed 7.7 kHz when the energy of the pump pulses is 36 J and the duration of these pulses is 300 μs.

1 Hz, 1 ps, terawatt Nd: glass laser

Chirped-pulse amplification of picosecond pulses is demonstrated in a compact Nd: glass laser system. A Nd: phosphate glass slab laser is used to produce terawatt pulses as a power amplifier. The detailed characterization of the zigzag slab amplifier is described. The laser system produces > 1 J, 1.0 ps pulses at a 1 Hz repetition rate.

High gain, diode-pumped Nd:YVO 4 slab amplifier

Single-pass, small signal gains of up to 400 in 1 cm have been measured for the amplification of a Nd:YAG probe beam in a simple, diode side-pumped Nd:YVO 4 slab amplifier using a single, grazing-incidence reflection. The useful small signal gain has been found to be limited by amplified spontaneous emission.

Generation of narrow-band radiation in a system with a monolithic ring YAG laser and a slab amplifier

A solid-state laser was developed on the basis of a highly stable cw narrow-band monolithic YAG laser pumped by semi-conductor diode lasers, a system for shaping a pulse of given duration, and a multipass slab amplifier. The spectral and power characteristics of the YAG laser acting as a master oscillator were investigated. An interferometric study was made of the thermal distortions of the laser beam in the slab amplifier where the ray paths were zigzag-shaped. The signal from the master oscillator was amplified by a factor of 7×104 in the four-pass slab amplifier without distortion of the spatial characteristics of the laser beam.

Performance of a degenerate KTiOPO_4 optical parametric oscillator, synchronously pumped by a mode-locked and Q-switched Nd:YAG continuous-wave oscillator–slab amplifier combination

We used a cw-pumped, Q-switched, and mode-locked Nd:YAG oscillator and a cw-pumped, multipass traveling-wave amplifier with a face-pumped total-internal-reflection Nd:YAG slab as the gain element to produce an 80-W, TEM00 diffraction-limited beam at a Q-switching rate of 10 kHz (50 W at 3 kHz). The output of this device was used to synchronously pump a degenerate optical parametric oscillator that utilized six KTiOPO4 crystals as nonlinear converters. A maximum average power of 14 W at 2.128 μm was generated with a conversion efficiency of 25% at 4.25 kHz.

Numerical and experimental investigation on ASE effects in high-power slab amplifiers

A three-dimensional calculation of the amplified spontaneous emission (ASE) is presented that allows rapid determination (with suitable approximation techniques) of the gain-length product (GLP) in high-power slab amplifiers. These calculations include non-saturable absorption, ASE line-narrowing effects, and total internal reflections (TIR) at the pumping surfaces. A parametric study of the slab geometry is presented and compared with experimental results. A good qualitative agreement between theory and experiment is achieved.

Design of a high-gain laser diode-array pumped Nd:YAG alternating precessive slab amplifier (APS amplifier)

In the design of space-qualifiable laser systems for ranging and altimetry, such as NASA's geodynamic laser ranging system (GLRS), the transmitter must be kept small, powerful yet efficient, and must consist of as few components as possible. The author reports on a unique preamplifier design which satisfies these requirements, and is suitable as the first amplifier stage following a laser, with an output of 1 mJ per pulse. It requires no external beam-steering optics, yielding a compact component with simple alignment procedures. The gains achieved are comparable to multipass zigzag amplifiers using two or more sets of external optics for extra passes through the amplifying medium.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Properties of a laser-plasma x-ray source for x-ray lithography

We have used an advanced, near diffraction limited Nd:YAG laser, operated at 1.06 μm and employing a zig-zag slab amplifier, to generate x rays from the laser induced plasmas of a number of target materials. The x-ray conversion efficiencies were studied as a function of target material and laser parameters. We have measured the x-ray spectra, for x-ray energies above about 1 keV, and used them to evaluate this source with regard to x-ray lithography. A number of target material, resist, and mask combinations appear suitable for a lithography system capable of 0.25-μm minimum feature size.

Eight-pass neodymium glass slab amplifier with a waveguide and with phase conjugation

An eight-pass amplifier was constructed from an active element of rectangular cross section and 74×24×4 cm dimensions. Its output energy was 170 J with an input energy of 5×10−4 J and a pulse duration of 20 nsec. The use of phase conjugation made it possible to compensate considerable distortions of the wavefront introduced by the active element. Over 50% of all the energy was concentrated in an angle of 7×10−5 rad.

A two-pass three-channel slab amplifier

A highly efficient slab amplifier has been designed. It has an aperture of 100 mm. The laser beam passes through the amplifier via three channels and then goes through it for the second time. Under typical conditions, we have obtained a gain of tenfold, an output intensity of 1011W [1], and an efficiency of 0.1 percent. By means of astigmatism compensation, the statical beam divergence after passing through 72 surfaces has been improved to 60 μrad, and the dynamic beam divergence to 0.2 mrad.

Choice of an optimum multichannel Nd:glass laser system for fusion experiments

A comparison has been made between proposed configurations for Nd-glass laser systems for fusion. Detailed theoretical modeling of pulse propagation has been carried out using a linearized model with the variables taken to be time, axial coordinate, and one transverse coordinate. A non-temporally varying, three-spatial dimension model was also used to correct the linearized two-spatial dimension calculations. A 10(5) J system using 200 slab amplifiers and 20 spatial filters and having a 10(-4) rad divergence appears feasible.