Strained Active Layer Surface Emitting Laser with Strain Compensation
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Solution Overview
Problem
Conventional surface emitting laser devices with highly strained active layers face issues of high threshold current and low optical output due to dislocation problems when attempting to increase modal gain by thinning the barrier layer, leading to operating limitations in speed and reliability.
Innovation Solution
A surface emitting laser device with a strained active layer and a current confinement layer that includes a selectively oxidized portion, positioned to influence the strained active layer, which compensates for strain and suppresses dislocation, allowing for increased optical confinement and reduced threshold current density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the thickness of the barrier layer is made thin to increase modal gain, then the optical confinement factor increases and threshold current decreases, but dislocation occurs in the quantum well layer and device reliability degrades
Solution Approach 1:
A strain compensation layer is introduced as an intermediary between the quantum well layer and the barrier layer. This layer mediates the strain stress that would otherwise cause dislocation, enabling the barrier layer to be made thinner for higher optical confinement while maintaining quantum well layer integrity and device reliability
Solution Approach 2:
The invention changes the physical parameters of the strain compensation layer, specifically setting its thickness to 5-20 nm and its composition to have a lattice constant between that of GaAs and GaInNAs. This parameter optimization allows the layer to effectively compensate strain without causing dislocation, enabling thin barrier layers to be used safely
2Reliability
If the thickness of the barrier layer is increased to prevent dislocation, then device reliability improves, but modal gain decreases and threshold current increases
Solution Approach 1:
The strain compensation layer acts as a mediator that allows the barrier layer to be made thinner than previously possible. By placing this intermediary layer between the quantum well and barrier layers, the patent achieves both thin barrier layers (for high modal gain) and dislocation prevention (for reliability)
Solution Approach 2:
The patent segments the barrier layer into two functional parts: the strain compensation layer (5-20 nm thick) that handles strain management, and the remaining barrier layer that provides optical confinement. This segmentation allows each layer to be optimized for its specific function, achieving both reliability and high optical output
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 enables low threshold current density and high-speed operation with improved reliability, achieving increased optical confinement and extended operational temperature ranges.
Implementation Method 1
The current confinement layer is arranged at a position where a strain in the selectively oxidized portion influences the strained active layer
Implementation Method 2
The current confinement layer includes a selectively oxidized portion
Implementation Method 3
an optical resonator arranged on the substrate, the optical resonator including a lower multilayer reflector and an upper multilayer reflector
Data Source
AI summary
An optical resonator including a lower multilayer reflector and an upper multilayer reflector is arranged on a substrate. A strained active layer having a multiple quantum well structure formed with a quantum well layer and a barrier layer is arranged in the resonator. A current confinement layer including a selectively oxidized portion is arranged on an upper side of the strained active layer. The current confinement layer is arranged at a position where a strain in the selectively oxidized portion influences the strained active layer.