Back-Emitting Laser Grid Structure for High Power Output
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Solution Overview
Problem
Conventional semiconductor laser designs face challenges in scaling power due to nonplanar bowing of the chip after bonding, which affects the alignment of mirror arrays and reduces consistent results in external cavity designs, leading to inefficient power output and beam quality.
Innovation Solution
A back-emitting epitaxial semiconductor laser structure with a micro-lens array on the back of the substrate, where each laser region has an aperture for controlled beam emission, allowing for non-coherent beam combination and improved beam quality, and using graphene lens structures to enhance beam focusing and coherence length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional external cavity laser designs are used with bonded chips, then laser power can be generated, but nonplanar bowing of the chip occurs after bonding which adversely affects mirror array alignment and reduces beam quality
Solution Approach 1:
The patent inverts the conventional approach by placing the mirror array on the backside of the laser chip rather than on the front. This allows the mirrors to be positioned on a planar reference surface that is not affected by the bowing of the chip front surface, thereby maintaining precise alignment while enabling high power output from multiple laser regions.
Solution Approach 2:
The patent transitions from a single-sided laser emission design to a backside-emitting design, utilizing the third dimension (chip thickness) to separate the laser emission surface from the mirror array mounting surface. This dimensional separation allows independent optimization of both the laser active regions and the optical cavity alignment.
2Power
If multiple laser regions are combined in an array configuration, then overall output power increases, but alignment of mirror arrays becomes increasingly difficult due to chip bowing
Solution Approach 1:
By inverting the mirror array placement to the chip backside, the patent eliminates the coupling between multiple laser region alignment and chip bowing. Each mirror can be independently aligned to its corresponding laser region through the planar backside surface, significantly reducing alignment complexity while enabling high-power array operation.
Solution Approach 2:
The patent divides the laser chip into multiple independent laser regions, each with its own mirror and optical cavity. This segmentation allows each region to be independently optimized and aligned without affecting others, facilitating scalable high-power array designs with reduced cumulative alignment complexity.
3Productivity
If the entire cavity is grown in a sequence of mirrors and active regions, then laser functionality is achieved, but bowing adversely affects the intra-cavity mirrors and optimizes only a few array elements at a time
Solution Approach 1:
The patent inverts the cavity structure by placing mirrors on the chip backside rather than within the bulk crystal structure. This separation allows the epitaxial growth to focus on optimizing individual laser regions without the constraint of maintaining planarity across the entire cavity, enabling full array optimization rather than just a few elements.
Solution Approach 2:
By segmenting the cavity into independent regions with individually optimized mirrors on the backside, the patent enables parallel optimization of all array elements during manufacturing, rather than requiring sequential adjustment of individual elements, thereby improving overall productivity.
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 achieves high-power, short-coherence-length beams with improved beam quality and reduced size, weight, and cost, suitable for applications like drone defense directed-energy weapons, while minimizing alignment complexities and increasing output power.
Implementation Method 1
Each lens 2610 can be aligned with a laser cavity 2602 in the substrate 2200 that terminates in an aperture at the back 2506 of the substrate 2200
Implementation Method 2
A back-emitting epitaxial semiconductor laser structure with a micro-lens array on the back of the substrate, where each laser region has an aperture for controlled beam emission
Implementation Method 3
each cavity is not adversely affected because the completion of the mirror stage which is a series of layers with a contrast in the materials refractive index is completed with the mirror or reflective layers on the wafer layer
Data Source
AI summary
Disclosed herein are various embodiments for laser apparatuses. In an example embodiment, the laser apparatus comprises (1) a laser-emitting epitaxial structure having a front and a back, wherein the laser-emitting epitaxial structure is back-emitting and comprises a plurality of laser regions within a single mesa structure, each laser region having an aperture through which laser beams are controllably emitted, (2) a micro-lens array located on the back of the laser-emitting epitaxial structure, wherein each micro-lens of the micro-lens array is aligned with a laser region of the laser-emitting epitaxial structure, and (3) a non-coherent beam combiner positioned to non-coherently combine a plurality of laser beams emitted from the apertures.