Semiconductor Laser Ridge Recess Structures for Circular Far Field Pattern
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Solution Overview
Problem
Semiconductor laser devices with an elliptical far field pattern (FFP) have a large aspect ratio between vertical and horizontal transverse modes, which is undesirable for achieving a more circular FFP shape.
Innovation Solution
A semiconductor laser device is designed by stacking a semiconductor layer, a dielectric film, and an electrode layer, featuring a ridge and recess structures that include first, second, and third grooves, with the dielectric film covering the semiconductor layer except for the ridge, to achieve a more circular FFP shape by optimizing the radiation angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional semiconductor layer structure with ridge and grooves is used, then the device is compact and lightweight with high reliability, but the far field pattern becomes elliptical with a large aspect ratio
Solution Approach 1:
The patent divides the semiconductor layer into multiple precisely positioned recesses (first, second, and third recesses) with different orientations and depths. These segmented structural elements independently control different aspects of the optical field, allowing the horizontal radiation angle to be widened while maintaining the vertical characteristics, thereby transforming the elliptical FFP into a more circular shape while preserving device reliability
Solution Approach 2:
The patent applies different recess configurations at specific locations within the semiconductor layer. The first recesses are positioned on both sides of the ridge, the second recesses extend from ends toward the center, and the third recesses are disposed at specific positions where the ridge is interposed. Each local region's recess structure is optimized to contribute differently to the overall FFP, with local quality variations enabling precise control over the radiation pattern's horizontal and vertical angles
2Device complexity
If the radiation angle in vertical transverse mode is maintained, then the device structure remains simple, but the aspect ratio becomes large causing elliptical FFP
Solution Approach 1:
The patent introduces a new dimensional aspect by adding recesses that extend in the lateral direction (third recesses disposed where the ridge is interposed) in addition to the conventional vertical groove structure. This dimensional expansion allows independent control of horizontal radiation angle without fundamentally altering the vertical mode structure, enabling circular FFP while maintaining relatively simple device structure
Solution Approach 2:
The patent employs asymmetric recess configurations where the first recesses are on both sides of the ridge, the second recesses extend from ends toward the center, and the third recesses are positioned specifically where the ridge is interposed between them. This asymmetric arrangement creates different effective widths in horizontal and vertical directions, allowing the horizontal radiation angle to be widened to match the vertical angle, thus achieving circular FFP without excessive structural complexity
Data Source
AI summary
In a semiconductor laser device, a semiconductor layer includes a first groove formed on both sides of a ridge, a pair of second recesses facing each other and between which the ridge is interposed on a side of a light emitting surface, and a pair of third grooves in parallel to the first groove from the light emitting surface and interposing the ridge therebetween.