Nitride Semiconductor Laser Ridge Grooves for Optical Confinement
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Solution Overview
Problem
Nitride semiconductor laser devices with ridge waveguide structures face challenges in maintaining good optical confinement and adhesion of protective films, leading to inconsistent performance and reliability issues due to factors like adhesion between the nitride semiconductor layer and protective film, which affect optical confinement and power output.
Innovation Solution
A nitride semiconductor laser device design featuring a ridge with continuous grooves on both sides, where the grooves have a width less than the ridge and a depth positioned in the second nitride semiconductor layer, enhancing optical confinement and adhesion by reducing leak current and improving refractive index differences, while an insulating film with varying thickness is applied to manage stress and refractive index differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective film is formed on the side surfaces of the ridge to improve adhesion, then adhesion is enhanced, but optical confinement deteriorates due to refractive index mismatch
Solution Approach 1:
The patent applies different thicknesses of the same insulating film material to different regions: a first thickness on the ridge side surfaces and a second (different) thickness in the grooves. This local differentiation allows the film to provide adhesion where needed while maintaining optical confinement by compensating for refractive index effects in specific locations.
Solution Approach 2:
The insulating film acts as an intermediary layer between the nitride semiconductor layer and the protective film. By carefully controlling its thickness distribution, it mediates between the conflicting requirements of adhesion (needing film coverage) and optical confinement (needing minimal interference with light propagation).
2Ease of manufacture
If the ridge width and depth are increased to improve optical confinement, then optical confinement is enhanced, but device complexity increases
Solution Approach 1:
The patent segments the ridge structure by introducing grooves that divide the ridge into multiple regions (ridge portions and groove portions). This segmentation allows independent optimization of optical confinement in the ridge regions while managing stress and adhesion in the groove regions, achieving better overall performance without requiring excessive increases in overall ridge dimensions.
Solution Approach 2:
Instead of simply increasing ridge width (one dimension), the patent introduces grooves that add vertical depth variation (another dimension). This dimensional approach allows optical confinement to be enhanced through the depth dimension via the insulating film thickness variation, rather than requiring proportional increases in width, thus managing device complexity.
3Reliability
If grooves are formed to reduce leak current and improve adhesion, then adhesion is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies particular parameter ranges for the grooves (width less than ridge width, depth positioning in the second nitride semiconductor layer) and insulating film thicknesses (first thickness on ridge, second thickness in grooves). These parameter specifications provide clear manufacturing targets that balance adhesion improvement with achievable precision levels, avoiding overly stringent requirements.
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 design achieves low threshold current, high luminous efficiency, and improved optical output power versus input current, ensuring long operating life and stable performance by enhancing optical confinement and adhesion, thus addressing the reliability issues of existing devices.
Implementation Method 1
an insulating film with varying thickness is applied to manage stress and refractive index differences
Implementation Method 2
improving refractive index differences
Implementation Method 3
enhancing optical confinement and adhesion by reducing leak current
Data Source
Figure 1(a)~1(b)
Figure 2~4
AI summary
The nitride semiconductor laser device includes a substrate (10), a nitride semiconductor layer having a first nitride semiconductor layer (21), an active layer (22), and a second nitride semiconductor layer (23) stacked in this order on the substrate (10), and a ridge (24) provided on a surface of the nitride semiconductor layer. The surface of the nitride semiconductor layer includes a generally flat part and first and second grooves (25) which extend along the ridge (24) in a resonator direction, the first groove being formed continuous to a first side surface of the ridge (24), the second groove being formed continuous to a second side surface of the ridge which is opposite to the first side surface.