Thin Disk Laser Amplifier Thermal Aberration Cancellation
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Solution Overview
Problem
High power laser amplifiers face challenges in achieving high gain while minimizing thermal aberrations, which limit laser brightness and efficiency due to nonlinear thermal effects and spontaneous stimulated emission, especially under high gain conditions.
Innovation Solution
A solid-state laser amplifier system using thin laser gain media with non-uniform pumping and angular multiplexing to cancel thermal aberrations, combined with cryogenic cooling to maintain a temperature-independent index of refraction, and incorporating absorbing materials to reduce accumulated stimulated emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the laser gain media is pumped at high power to achieve high gain, then the laser amplification capability is improved, but the temperature of the gain media increases causing thermal aberrations that worsen beam quality
Solution Approach 1:
The patent transitions from conventional rod-shaped gain media to a thin disk geometry, changing the dimensional configuration to reduce thermal path length. This allows heat to be conducted away more efficiently in the thickness direction while maintaining a large pump absorption area in the plane direction, thereby achieving high gain with reduced thermal aberrations
Solution Approach 2:
The patent changes the geometric parameters of the gain media from a rod configuration to a thin disk configuration with specific thickness and diameter ratios. This parameter change enables the gain media to operate at high pump powers while maintaining acceptable thermal gradients through optimized heat conduction pathways
2Productivity
If the pump light is focused to the smallest area to achieve maximum gain per unit length, then the gain efficiency is improved, but the heat deposited per unit area increases compounding thermal aberrations
Solution Approach 1:
By adopting a thin disk geometry with large diameter and small thickness, the patent distributes the pump heat load over a large surface area while maintaining short thermal conduction paths. This dimensional change allows high pump power density to be achieved without excessive localized heating, as heat can be efficiently conducted away through the thin thickness direction
3Temperature
If conventional cooling methods are used to remove heat from the gain media, then thermal management is improved, but the index of refraction becomes temperature-dependent causing thermal lensing and aberrations
Solution Approach 1:
The thin disk geometry creates a favorable thermal management configuration where heat is conducted away in the thickness direction perpendicular to the large pump absorption area. This dimensional arrangement enables efficient cooling while minimizing temperature gradients in the directions that would cause thermal lensing and aberrations
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables high gain and high power amplification with improved beam quality by effectively managing thermal aberrations and ASE, allowing for more compact and efficient laser systems.
Implementation Method 1
a light beam shaping optical system positioned adjacent to the pumping light source for shaping and directing a pump light beam from said pumping light source into a first surface of said at least one laser-active solid
Implementation Method 2
the laser-active solid is slab-shaped and is fixedly connected at a second surface thereof to the cooling device, and wherein a major portion of heat generated in the laser-active solid by the pump light is removed by the cooling device
Implementation Method 3
an optical system configured to bring the laser beam to be amplified into the laser active solid at an angle to a normal to the first surface of the laser active solid to remove substantially nonparallel isotherms that arise from nonuniform pumping
Implementation Method 4
said channels being filled with an absorbing material or scattering centers to introduce regions of absorption and scattering losses along a direction defined by L1 and prevent accumulated stimulate emission along the L1′ pumped region
Data Source
AI summary
The present invention discloses a laser amplifier with high gain and low thermally induced optical aberrations on the amplified laser beam. The amplifier designs allow simple multipass configurations to optimally extract the gain and reduce thermally induced index of refraction aberrations, making it possible to obtain an amplified laser beam of high quality combined with very high overall gains comparable to those achievable with expensive regenerative amplifiers. The amplifier includes a thin active laser solid to create the population inversion and associated heat generation within the thin laser active solid possible for the desired gain value. The system includes a cooling device in thermal contact with the thin active laser solid to provide good heat transport and high reflectivity coatings at the wavelengths of the pump and laser wavelengths. The pump light sources are laser diodes tuned to the maximum absorption of the laser active material. The amplifier also includes an optical system to transport the pump light to the laser active solid in such a way as to further confine the absorption of light along the two orthogonal directions in the plane of the laser active solid in order to get high population inversion and consequently high gains possible.