Tilted Spatial Filter for Laser Amplifier Feedback Reduction
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Solution Overview
Problem
High pulse energy laser systems face limitations due to parasitic optical feedback from stray reflections and scattering, which reduce the maximum gain and energy storage in the laser amplifier medium, leading to unwanted ASE and spurious lasing.
Innovation Solution
A device comprising a flat plate with a reflecting or absorbing surface oriented at an angle to the laser beam path and featuring an aperture that allows the desired laser beam to pass through while preventing optical noise from returning to the laser oscillator or amplifier, effectively isolating the stages and reducing spontaneous fluorescence photons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If Faraday isolators are used to block reflected light, then optical feedback is reduced, but they are only applicable to polarized laser light and have relatively low transmission which reduces energy efficiency
Solution Approach 1:
The patent extracts and removes the harmful reflected light from the optical path using a beam dump positioned at an angle, separating the useful forward-propagating laser beam from the harmful backward-reflected light, thereby eliminating optical feedback without affecting energy transmission
Solution Approach 2:
The patent introduces a beam dump as an intermediary element that selectively intercepts only the reflected light while allowing the primary laser beam to pass through unaffected, serving as a mediator that blocks harmful feedback without reducing energy efficiency
2Object-affected harmful factors
If optics are tilted at small angles to deflect reflections, then stray photons are reduced, but the optical elements are placed in off-axis arrangement which adversely affects beam quality
Solution Approach 1:
The beam dump acts as an intermediary that intercepts stray photons and reflections without requiring the optical elements themselves to be tilted, thereby maintaining proper optical alignment and beam quality while still eliminating harmful stray light
Solution Approach 2:
The patent extracts the function of stray light deflection from the optical elements themselves and relocates it to a separate beam dump component, allowing the optics to remain in optimal on-axis positions for beam quality while still achieving stray photon reduction
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
This solution significantly reduces parasitic lasing and increases energy storage and gain in the laser amplifier, enhancing the energy extraction efficiency and preventing disruption from optical noise.
Implementation Method 1
A device is introduced consisting of a flat plate with an aperture and a reflecting or absorbing surface at an angle to the common optical axis
Implementation Method 2
A device is introduced consisting of a flat plate with an aperture and a reflecting or absorbing surface at an angle to the common optical axis
Implementation Method 3
The device consists of a flat plate with an aperture and a reflecting or absorbing surface at an angle to the common optical axis of the laser oscillator and laser amplifier
Data Source
Figure 1
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AI summary
A device for reducing spontaneous emission in laser oscillator laser amplifier laser system. A MOPA (100) comprises a master oscillator (104) and a power amplifier (112) and between them on the optical axis (204) a tilted spatial filter (208) having a reflecting surface (212) and an aperture (216). The oscillator beam (108) passes the filter via the aperture nearly undamped while ASE (120) emitted from the amplifier (112) travelling in the direction of the oscillator (104) is mainly reflected off the optical axis by the plate (208).