Back-Pumped Membrane Laser With Reflective Pump-Coupling Layer
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Solution Overview
Problem
Current optically pumped semiconductor lasers face challenges with high costs and inefficient thermal management due to the need for expensive pump sources and limited heat dissipation, making them unsuitable for mass production and wide wavelength ranges.
Innovation Solution
A back-pumped semiconductor membrane laser design featuring a planar-shaped lasing medium with a first dielectric layer that is highly reflective for the laser wavelength and partially transmissive for the pump wavelength, allowing for optimized pump geometry and improved thermal management through a sandwiched heat spreader configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If expensive pump sources with good beam quality are used to achieve lasing, then the power density in the active region is sufficient to cause lasing, but the manufacturing cost increases significantly
Solution Approach 1:
The patent inverts the conventional pumping geometry by pumping the semiconductor laser from the backside (through the substrate) rather than from the front. This allows the use of cheaper pump sources with less stringent beam quality requirements, as the pump light enters through the substrate and is focused onto the active region from the opposite direction, eliminating the need for expensive pump optics with precise beam control
Solution Approach 2:
The patent changes the spatial dimension of pumping by transitioning from lateral/side pumping to vertical backside pumping through the substrate. This dimensional change allows the pump beam to enter through the substrate plane rather than from the side, enabling the use of simpler, less expensive pump sources while maintaining effective pumping of the active region
2Power
If the focusing lens size is increased to improve pump beam focusing, then the pump power density increases, but the geometric constraints due to the 900 angle between amplifier medium and laser beam limit the available space
Solution Approach 1:
By inverting the pumping direction to backside pumping, the patent eliminates the geometric conflict between the focusing lens and the laser beam extraction path. The pump beam enters through the substrate from the back, allowing the focusing lens to be positioned without interfering with the front-side laser output, thus removing the 900 angle geometric constraint
Solution Approach 2:
The patent relocates the pumping operation to another dimension (through the substrate from the back) rather than from the side. This spatial reconfiguration allows the focusing optics to be positioned in a different plane, eliminating the geometric interference between the pump focusing lens and the laser beam extraction path
3Power
If more pump power is used to compensate for poor heat dissipation, then the lasing power increases, but additional heat is generated which requires even more pump power density
Solution Approach 1:
The patent introduces the substrate as an intermediary heat dissipation path. The substrate serves as a thermal conductor that efficiently removes heat from the active region during backside pumping, acting as a heat sink that prevents thermal accumulation. This intermediary heat management system allows for sustained high-power operation without the thermal runaway that would otherwise require reduced pump power
4Temperature
If individual heat spreaders are installed to improve thermal management, then heat dissipation improves, but the manufacturing cost and device complexity increase
Solution Approach 1:
The patent makes the substrate multi-functional by having it serve both as the mounting platform for the active region and as the primary heat dissipation pathway. The substrate simultaneously provides mechanical support, electrical isolation, and thermal management functions, eliminating the need for separate heat spreader components and simplifying the overall device structure for mass production
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 design enables cost-effective mass production of semiconductor membrane lasers with enhanced thermal management and reduced manufacturing costs, while maintaining high optical output and beam quality across a wide range of wavelengths.
Implementation Method 1
a first dielectric layer that is highly reflective for the laser wavelength
Implementation Method 2
partially transmissive for the pump wavelength
Implementation Method 3
sandwiched heat spreader configuration
Data Source
AI summary
A semiconductor membrane laser chip includes a planar-shaped lasing medium having an upper surface and a lower surface opposite the upper surface, the lasing medium configured to emit electromagnetic radiation at a laser wavelength λ1. A first heat spreader is bonded to one of the upper surface and the lower surface of the lasing medium. A first dielectric layer is arranged on the lower surface of the lasing medium or arranged on a lower surface of the first heat spreader when the first heat spreader is bonded to the lower surface of the lasing medium. The first dielectric layer is reflective for the laser wavelength λ1.