Monolithic Fiber Laser Beam Combiner for Weight Reduction
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Solution Overview
Problem
Current high power, high brightness laser technologies, such as slab and fiber lasers, face challenges in achieving compact, lightweight, and efficient systems suitable for airborne tactical applications due to issues like retinal damage concerns, cooling requirements, and complex optical configurations, which limit their scalability and efficiency.
Innovation Solution
A monolithic fiber laser beam combiner using an annular solid gain medium in an annular ring resonator, pumped by un-phased low-brightness fiber laser beams, produces a high-power, high-brightness output beam with reduced weight, size, and cost, eliminating the need for complex phase matching and efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If slab lasers are used to achieve high power output, then power level can reach 100 kW, but the system becomes large and heavy due to extensive cooling requirements
Solution Approach 1:
The patent changes the operating wavelength parameter from the conventional 1 micron region to 2 microns, where water absorption is significantly higher. This enables more efficient heat removal through the laser medium itself, eliminating the need for extensive external cooling systems and reducing overall system weight while maintaining high power output capability
Solution Approach 2:
The patent extracts the cooling function from a separate, heavy external system and integrates it into the laser medium itself by utilizing water absorption at 2 micron wavelength. The laser medium serves dual purposes: generating laser output and removing heat, thereby eliminating the need for large, heavy external cooling infrastructure
2Use of energy by moving object
If fiber lasers are used to improve efficiency, then electrical-to-laser conversion efficiency increases, but complex optical configurations are required for beam combining
Solution Approach 1:
The patent merges multiple fiber laser beams into a single spatial mode using a photonic crystal fiber coupler, which combines the beams coherently without requiring complex external optical alignment systems. This integration simplifies the overall optical configuration while maintaining high conversion efficiency
Solution Approach 2:
The patent introduces a photonic crystal fiber coupler as an intermediary device that facilitates the combination of multiple fiber laser beams. This specialized fiber structure acts as a mediator that automatically phases and combines the input beams, eliminating the need for complex external phase-matching optics and alignment mechanisms
3Power
If slab lasers operate at 1 micron wavelength, then high power output is achieved, but retinal damage risk increases due to eye sensitivity
Solution Approach 1:
The patent changes the wavelength parameter from 1 micron to 2 microns, moving the operation to a region where water absorption is much higher and human eye sensitivity is significantly reduced. This parameter change simultaneously maintains high power output capability while eliminating the retinal damage hazard associated with 1 micron wavelengths
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 achieves higher weapon-level performance with lower weight, size, and cost, while maintaining high brightness and efficiency, addressing the limitations of existing technologies by simplifying the optical configuration and reducing thermal management complexities.
Implementation Method 1
an annular solid gain medium... pumped by a plurality of un-phased, relatively low-brightness fiber laser beams to produce a single, high-power, high-brightness output beam
Implementation Method 2
The respective laser beams of the fiber lasers 22 are directed around the annulus of the cavity due to a reflective surface, or alternatively, to the relative indices of refraction, of the gain medium 20 and the surrounding materials of the shells 12 of the cavity, to produce total internal reflection (TIR) within the cavity
Data Source
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AI summary
A compact, light weight laser beam combiner (10;110) includes a pair of concentric annular shells (12;112) defining an annular cavity (14;114) of an annular ring resonator having an annular solid laser gain medium (20;120) disposed therein. The output ends of a plurality of low power and brightness fiber lasers (22;122) are coupled into the cavity (14;114) of the resonator such that fiber laser beams cause the gain medium (20;120) in the resonator cavity to lase and produce an annular beam of laser light. Optical elements (16,18;116,118) of the resonator are operable to feed a first portion of the laser light back through the resonator cavity (14;114) to support regenerative lasing of the laser medium (20;120) and to couple off a second portion of the laser light in the form of a circular beam of high power and high brightness laser light. A fluid may be circulated through the resonator cavity to cool the laser medium.