Surface-Emitting Laser Polarization Stabilization via Strain Field
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Solution Overview
Problem
Existing surface-emitting lasers for image forming apparatuses face challenges in maintaining stable polarization of light, with previous methods either lacking stability, increasing costs, or affecting the shape of the light beam, especially under varying temperatures or long-term operation.
Innovation Solution
A surface-emitting laser design featuring a substrate with a normal inclined to specific crystal orientations, incorporating a semiconductor multilayer mirror and a selective oxidation layer with a strain field, where the oxidation rate varies anisotropically, stabilizing the polarization state without impacting the light beam's shape and maintaining cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an inclined substrate is used to control polarization state, then polarization control is achieved, but stability deteriorates when temperature increases or operation time extends
Solution Approach 1:
The invention changes the physical-chemical parameters of the selective oxidation layer by controlling its thickness to be 5 nm or less, and by adjusting the aluminum content in the aluminum-containing semiconductor layer. This parameter optimization creates a strain field that stabilizes the polarization state without the instability issues of inclined substrates
Solution Approach 2:
The invention applies local quality by creating a selective oxidation layer only in specific regions where aluminum-containing semiconductor layers are present, rather than uniformly across the entire structure. This localized oxidation generates the necessary strain field while maintaining overall structural stability
2Ease of operation
If anisotropic stress is applied to the active layer to control polarization, then polarization control is achieved, but manufacturing complexity increases and costs rise due to limited wire pull-out directions and inability to use isotropic dry etching
Solution Approach 1:
The invention replaces mechanical stress application methods with a chemical field approach. By forming a selective oxidation layer, a strain field is generated that controls polarization without requiring mechanical wire pull-out or complex etching processes, enabling use of isotropic dry etching and reducing manufacturing costs
Solution Approach 2:
The selective oxidation layer acts as an intermediary that generates the necessary strain field for polarization control. Instead of directly applying mechanical stress or using complex manufacturing processes, the oxidation layer mediates the creation of a strain field that achieves the desired polarization effect
3Ease of operation
If a selective oxidation layer with rectangular or oval shape is used to control polarization, then polarization control is achieved, but the shape of the light beam is adversely affected
Solution Approach 1:
The invention changes the thickness parameter of the selective oxidation layer to be extremely thin (5 nm or less), which allows the strain field to be generated without significantly disturbing the light beam propagation. This thin thickness ensures the light beam maintains its natural shape while still achieving polarization control through the strain field
4Ease of operation
If a selective oxidation layer with uneven thickness is used to control polarization, then polarization control is achieved, but MOCVD cannot be used for production, increasing production costs
Solution Approach 1:
The invention uses local quality by forming the selective oxidation layer only in regions with aluminum-containing semiconductor layers, while maintaining uniform thickness (5 nm or less) throughout. This localized yet uniform approach allows MOCVD to be used for production, avoiding the cost increase associated with uneven thickness control
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 stable polarization of light with a circular far-field pattern, maintaining high-quality image formation across varying conditions without increasing production costs, ensuring long-term reliability and efficiency in image forming apparatuses.
Implementation Method 1
a confined structure where a current passage area is surrounded by an oxidized area including at least an oxide generated by oxidation of a part of a selective oxidation layer containing aluminum
Implementation Method 2
A strain field caused by the oxidation is present at least in a part of the vicinity of the oxidized area surrounding the current passage area
Implementation Method 3
A normal of a principal plane of the substrate is inclined with respect to one of crystal orientations <100> toward one of crystal orientations <110>
Data Source
AI summary
A disclosed surface-emitting laser includes a substrate and multiple semiconductor layers stacked on the substrate. A normal of the principal plane of the substrate is inclined with respect to one of crystal orientations <1 0 0> toward one of crystal orientations <1 1 1>. The semiconductor layers include a resonator structure including an active layer; and a semiconductor multilayer mirror stacked on the resonator structure. The semiconductor multilayer mirror includes a confined structure where a current passage area is surrounded by an oxidized area including at least an oxide generated by oxidation of a part of a selective oxidation layer containing aluminum. A strain field caused by the oxidation is present at least in a part of the vicinity of the oxidized area. In the strain field, the amount of strain in a first axis direction is different from the amount of strain in a second axis direction.