Surface-Emitting Laser Resonator With Strain Relaxation Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional surface-emitting lasers with multi-junction structures face challenges in achieving high output power due to accumulated crystal distortion and strain in the resonator area, leading to crystal defects and reduced performance.
Innovation Solution
The surface-emitting laser device incorporates multiple active layers with controlled crystal strain, a tunnel junction layer, and strain relaxation layers to manage and reduce crystal strain, thereby preventing defects and enhancing output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple active layers are included in the multi-junction surface-emitting laser to increase output power, then the laser output power increases, but crystal distortion accumulates and crystal defects occur
Solution Approach 1:
A strain relaxation layer is introduced as an intermediary component between the active layers and the lower Bragg reflector. This strain relaxation layer has a lattice constant different from the active layers, allowing it to absorb and relax the accumulated crystal strain. By placing this mediator layer, the patent prevents strain accumulation in the active layers while maintaining multiple layers for high power output, thus resolving the contradiction between increasing power and preventing crystal defects
Solution Approach 2:
The patent changes the lattice constant parameter of the strain relaxation layer to be different from that of the active layers. This parameter change allows the strain relaxation layer to have different mechanical properties, enabling it to absorb strain effectively. By adjusting this fundamental material parameter, the patent creates a layer that can handle the mechanical stress without affecting the optical performance of the active layers
2Power
If the total thickness of active layers exceeds the critical film thickness, then more active layers can be stacked for higher power, but misfit dislocations occur due to accumulated strain
Solution Approach 1:
The strain relaxation layer serves as a buffer intermediary between the thick stack of active layers and the substrate/Bragg reflector structure. This intermediary layer absorbs the mechanical stress that would otherwise propagate through the entire structure and cause misfit dislocations. By introducing this buffer, the patent enables stacking of multiple active layers beyond what would be possible in a conventional structure without compromising crystal integrity
3Ease of manufacture
If GaInNAs, GaNAs, or GAPsb is used for the tunnel junction layer, then multi-junction structure can be formed, but high power output is still difficult to achieve
Solution Approach 1:
The patent uses a composite structure combining conventional semiconductor materials (GaAs, AlGaAs) for the active layers and tunnel junction layers with a strain relaxation layer made of materials having different lattice constants. This composite approach allows the tunnel junction layer to maintain its electrical function while the strain relaxation layer handles the mechanical stress, enabling both ease of manufacture and high power output
Data Source
AI summary
A surface-emitting laser device includes: a first reflector; a second reflector; and a resonator region between the first reflector and the second reflector. The resonator region includes: multiple active layers each having first crystal strain in one of a compression direction and a tension direction; a tunnel junction layer between the multiple active layers; and a strain relaxation layer having second crystal strain in another of the compression direction and the tension direction opposite to the first crystal strain of the multiple active layers.