Surface Emitting Semiconductor Laser With Dual Confinement Layers
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Solution Overview
Problem
Surface emitting semiconductor lasers face challenges in achieving efficient oscillation in fundamental transverse mode while restricting high-order higher mode oscillation, often resulting in high current thresholds and optical output variations due to inadequate optical and current confinement designs.
Innovation Solution
The design incorporates a surface emitting semiconductor laser with a two-layer oxidation structure, including a first and second oxidation confinement layer, and a reflectivity adjustment member that creates a higher optical loss in the periphery than the center, ensuring Do1 < Do2 and Dn < Do2, where Do1 and Do2 are the widths of the light and current confinement regions, and Dn is the width of the center portion of the reflectivity adjustment member, to promote fundamental transverse mode oscillation and restrict high-order modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer confinement structure is used, then the device complexity is low, but the optical and current confinement efficiency is insufficient, resulting in high current thresholds and mode oscillation instability
Solution Approach 1:
The confinement structure is segmented into two distinct layers: a current confinement layer and an optical confinement layer. Each layer is optimized for its specific function, with the current confinement layer controlling carrier injection and the optical confinement layer guiding light propagation. This segmentation enables independent optimization of electrical and optical performance, resolving the contradiction between reliability and complexity.
Solution Approach 2:
Different regions of the device are assigned different functional properties. The center region (with diameter Dn) provides high reflectivity for fundamental mode oscillation, while the periphery region provides optical loss to suppress higher-order modes. The current confinement layer is positioned to match the optical confinement region (Do1 < Do2), creating localized quality differences that stabilize mode oscillation without requiring complex overall structure.
2Power
If the optical confinement region is enlarged to improve light output, then the optical output increases, but the current threshold increases due to larger active region area
Solution Approach 1:
The optical confinement layer creates a localized high-refractive-index region with diameter Do1 that is smaller than the current confinement region diameter Do2. This local quality difference allows the light to be confined to a small active area (reducing current threshold) while the periphery region provides additional optical path for light extraction (maintaining optical output). The reflectivity adjustment member with center portion diameter Dn further enhances this effect by providing selective reflectivity.
3Use of energy by moving object
If the current confinement region is reduced to lower the current threshold, then the current efficiency improves, but the optical confinement becomes insufficient, leading to mode oscillation instability
Solution Approach 1:
The device structure is segmented into distinct current and optical confinement functions. The current confinement layer (with region diameter Do2) is separated from the optical confinement layer (with region diameter Do1), allowing the current region to be larger for efficient carrier injection while the optical region remains smaller for stable mode oscillation. This functional segmentation resolves the contradiction between current efficiency and mode stability.
Solution Approach 2:
The optical confinement layer acts as an intermediary between the current confinement layer and the active region. It receives carriers from the larger current confinement region and confines them to the smaller optical confinement region, enabling both efficient current injection and stable optical oscillation. The reflectivity adjustment member serves as another intermediary that mediates between the confined light and the external optical field.
4Reliability
If a reflectivity adjustment member with complex structure is added to control mode oscillation, then the mode stability improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The reflectivity adjustment member implements local quality variation with a simple geometric structure: a center portion with diameter Dn surrounded by a periphery portion. The center portion provides high reflectivity for fundamental mode oscillation, while the periphery portion provides optical loss to suppress higher-order modes. This simple local differentiation achieves effective mode control without complex manufacturing processes.
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 configuration effectively reduces the resistance of the semiconductor laser, increases output, and maintains a low current threshold by confining light and current efficiently, thereby enhancing the stability and efficiency of the laser's oscillation modes.
Implementation Method 1
an optical confinement layer that confines light generated in the active region
Implementation Method 2
a current confinement layer that confines current flowing in the active region
Data Source
AI summary
A surface emitting semiconductor laser includes a substrate; a first semiconductor distributed bragg reflector of a first conductive type; an active region; a second semiconductor distributed bragg reflector of a second conductive type; a current confinement layer that confines current in the active region; an optical confinement layer that confines light in the active region; and an optical loss unit including center and periphery portions in a predetermined direction, and gives a larger optical loss to the periphery portion than that of the center portion. Also, Do1<Do2 and Dn<Do2 are satisfied, where Do1 is a width of an optical confinement region of the optical confinement layer in the predetermined direction, Do2 is a width of a current confinement region of the current confinement layer in the predetermined direction, and Dn is a width of the center portion of the optical loss unit in the predetermined direction.