Surface-Emitting Laser Relief Structure Alignment
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Solution Overview
Problem
Existing surface-emitting lasers face challenges in achieving precise alignment of the center position of the surface relief structure and current confinement structure, which affects the introduction of sufficient loss difference between the fundamental and higher order transverse modes, leading to inefficient single mode oscillations and reduced optical output.
Innovation Solution
A method involving three etch stop layers is used to form a surface relief structure with a stepped design, where the total thickness of the lower, middle, and upper layers is equal to an odd multiple of the ¼ wavelength, allowing for precise alignment and formation of a surface relief structure that introduces a sufficient loss difference between modes, thereby enhancing single transverse mode oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a surface relief structure is formed to suppress higher order mode oscillations, then single mode oscillation efficiency is improved, but manufacturing precision is degraded due to difficulty in achieving precise alignment between the surface relief structure and current confinement structure
Solution Approach 1:
The patent applies preliminary action by forming the surface relief structure before forming the current confinement structure. The surface relief structure is created on the upper reflecting mirror first, then the current confinement structure is formed subsequently through selective oxidation. This sequence ensures that the surface relief structure serves as a pre-established reference for mode control, while the current confinement structure is aligned to it during the oxidation process, thereby achieving precise alignment and suppressing higher order mode oscillations.
2Reliability
If the depth of the surface relief structure is increased to introduce sufficient loss difference between modes, then higher order mode suppression is improved, but manufacturing precision is degraded due to difficulty in controlling the exact depth
Solution Approach 1:
The patent applies parameter changes by optimizing the depth of the surface relief structure to be within the range of 0.05 to 2.0 micrometers. This specific depth range ensures that the optical path difference between the fundamental mode and higher order modes is sufficient to create the necessary loss difference for mode suppression, while remaining within the controllable precision of standard semiconductor fabrication processes. The depth parameter is carefully selected to balance mode control effectiveness with manufacturing feasibility.
3Reliability
If the confinement diameter is reduced to achieve single transverse mode, then mode control is improved, but optical output is degraded due to reduced light emission region
Solution Approach 1:
The patent applies local quality by creating a surface relief structure with spatially varying reflectance properties. The upper reflecting mirror is designed with a central region having high reflectance and a peripheral region with lower reflectance. This local variation in reflectance quality allows the fundamental mode (concentrated in the center) to experience high reflection and low loss, while higher order modes (extending to the periphery) experience lower reflection and higher loss. Consequently, single mode oscillation is achieved without requiring a reduced confinement diameter, thereby maintaining 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
This approach enables precise alignment and formation of a surface relief structure that suppresses higher order mode oscillations while maintaining high optical output, achieving efficient single transverse mode operation.
Implementation Method 1
the reflectance distribution of a peripheral region surrounding the center region of the light emission region that corresponds to a light emission center region is made lower than that of the center region by forming a stepped structure by means of a semiconductor layer
Data Source
AI summary
A method of manufacturing a surface-emitting laser that allows precise alignment of the center position of a surface relief structure and that of a current confinement structure and formation of the relief structure by means of which a sufficient loss difference can be introduced between the fundamental transverse and higher order transverse mode. Removing the dielectric film on the semiconductor layers and the first-etch stop layer along the second pattern, using a second- and third-etch stop layer are conducted in single step after forming the confinement structure. The relief structure is formed by three layers including a lower, middle and upper layer, and total thickness of three layers is equal to the optical thickness of an odd multiple of ¼ wavelength (λ: oscillation wavelength, n: refractive index of the semiconductor layer). The layer right under the lower layer is the second-etch stop layer and the first-etch stop layer is laid right on this etch stop layer.