Multipass Laser Amplifier With No-Power Beam Steering
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Solution Overview
Problem
Conventional multipass laser amplifiers face challenges in achieving high average power amplification due to optical nonlinear effects and thermal lensing, which limit the extraction of high peak power and cause damage to the gain crystal, especially when using small pump beam sizes.
Innovation Solution
The use of no-optical-power beam steering elements (BSEs) that steer the seed beam through a laser-pumped gain crystal without significant focusing, maintaining a large beam size to prevent damage and minimize thermal aberrations, allowing for high average power amplification up to 50-100 watts with a net gain of 50,000.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a small pump beam size is used in a bulk crystal amplifier, then the amplifier can be more compact, but optical nonlinear effects and thermal lensing increase, limiting peak power extraction and causing damage to the gain crystal
Solution Approach 1:
The patent transitions from a single-pass configuration to a multipass configuration, effectively adding the dimension of multiple beam passes through the gain crystal. This allows the beam to interact with a larger effective volume of the gain medium without requiring a physically larger crystal or pump beam, thereby maintaining compactness while reducing intensity-related harmful effects through distributed interaction.
Solution Approach 2:
The patent changes the operational parameters by implementing multiple passes through the gain crystal, which effectively increases the interaction length and distributes the energy extraction across multiple lower-intensity interactions rather than a single high-intensity interaction, thereby reducing optical nonlinear effects and thermal lensing.
2Device complexity
If a one-pass amplifier configuration is used, then the device is simpler and more compact, but the amplification is insufficient for high average power generation
Solution Approach 1:
The patent implements a multipass configuration where the laser beam continuously interacts with the gain medium multiple times in sequence, extending the useful amplification action beyond a single pass. This continuous interaction extracts more energy from the pumped gain crystal, enabling high average power generation while maintaining a relatively simple single-crystal architecture.
Solution Approach 2:
The patent uses a pump laser to pre-excite the gain crystal before the seed beam passes through, creating a population inversion that is then exploited multiple times across different passes. This preliminary pumping action enables sustained high-power amplification across multiple beam passes through the same crystal volume.
3Power
If regenerative amplifiers are used to achieve very high amplification, then the amplification level increases, but the system becomes more complex and expensive due to optical switching and closed loop requirements
Solution Approach 1:
The patent extracts the essential amplification function from the complex regenerative amplifier architecture by using a simplified multipass configuration through a single gain crystal without requiring optical switching, closed loops, or fast modulators. The useful amplification action is separated from the unnecessary complexity of regenerative designs.
Solution Approach 2:
The patent replaces expensive, complex regenerative amplifier components (fast optical switches, closed-loop resonators) with a simpler, more affordable single-pass-through-multiple-times configuration using basic optical elements and a single gain crystal, achieving comparable amplification at lower cost and complexity.
4Power
If multiple mirror pairs are used to achieve multiple passes through the gain crystal, then the amplification increases, but the design becomes complex and bulky
Solution Approach 1:
The patent merges the functions of multiple separate mirror pairs into a single integrated multipass configuration through one gain crystal, reducing the number of discrete optical components and their associated alignment requirements while achieving the same multiple-pass amplification effect.
Solution Approach 2:
The single gain crystal in the multipass configuration serves multiple functions simultaneously: it provides the gain medium for amplification, acts as the interaction volume for multiple beam passes, and eliminates the need for separate optical components that would be required in a multi-crystal or multi-mirror-pair configuration.
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
The solution enables the amplification of continuous-wave or pulsed laser beams to high average power with improved mode quality and reduced risk of parasitic effects, making the multipass laser amplifiers suitable for micromachining applications with compact and simple optical layouts.
Implementation Method 1
The beam-steering element has no optical power and is configured to deflect a laser beam, by refraction or diffraction, for each of multiple passes of the laser beam
Implementation Method 2
The beam-steering element has no optical power and is configured to deflect a laser beam, by refraction or diffraction, for each of multiple passes of the laser beam
Implementation Method 3
a laser resonator, that generates a beam of laser radiation, and one or more laser amplifiers that amplify the power of this beam
Data Source
AI summary
A multipass laser amplifier includes a mirror, a mirror device, a gain crystal, and refractive or diffractive beam-steering element. The gain crystal is positioned on a longitudinal axis of the multipass laser amplifier between the mirror and the mirror device. The beam-steering element is positioned on the longitudinal axis between the gain crystal and the mirror device. The beam-steering element has no optical power and deflects a laser beam, by refraction or diffraction, for each of multiple passes of the laser beam between the first mirror and the mirror device, such that each pass goes through the gain crystal for amplification of the laser beam and goes through a different respective off-axis portion of the beam-steering element. The no optical power of the beam-steering element enables maintaining a large beam size in the gain crystal, thereby facilitating amplification to high average power.