Semiconductor Laser Ridge Structure for Stray Light Suppression
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Solution Overview
Problem
Existing semiconductor lasers suffer from interference fringes in the far-field pattern due to the generation of stray light, which hinders the formation of a clear light spot.
Innovation Solution
The semiconductor laser device incorporates a multilayer structure with a ridge portion, bank, and light shielding groove to guide and shield stray light, utilizing an asymmetric cladding layer with a higher refractive index in the lower cladding layer and a light shielding groove that reaches the absorption layer to absorb stray light, thereby suppressing interference fringes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional semiconductor laser structure is used, then the device is simple and easy to manufacture, but interference fringes are generated in the far field pattern due to stray light
Solution Approach 1:
The semiconductor laser structure is segmented into multiple functional regions: a ridge portion for light emission, a bank portion adjacent to the ridge, and a light shielding groove between them. This segmentation allows each portion to serve its specific function while preventing stray light from the bank from reaching the emission region, thereby eliminating interference fringes without significantly complicating manufacturing
Solution Approach 2:
The harmful stray light generated in the bank portion is extracted and blocked by introducing a light shielding groove. This groove physically removes the stray light path from the overall light emission system, preventing it from reaching the far field pattern and causing interference fringes
2Object-generated harmful factors
If a light shielding groove is introduced to block stray light, then interference fringes are suppressed, but the device structure becomes more complex
Solution Approach 1:
The light shielding groove is introduced only in the specific local region where stray light generation occurs between the ridge and bank portions. This localized approach addresses the interference problem precisely where it arises without requiring complex modifications to the entire laser structure, maintaining overall structural simplicity while achieving the desired effect
3Object-generated harmful factors
If the light shielding groove does not reach the absorption layer, then manufacturing is easier, but stray light is not effectively absorbed and interference fringes persist
Solution Approach 1:
The light shielding groove is designed to extend through the cladding layers and reach the absorption layer at the bottom, performing the light absorption function in advance before stray light can propagate to the far field. This preliminary action ensures complete stray light elimination while the groove depth is controlled within manufacturable limits by designing it to stop at the absorption layer interface
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 effectively reduces stray light emission, preventing interference fringes and ensuring a clear light spot formation by enhancing light absorption and reducing internal losses.
Implementation Method 1
utilizing an asymmetric cladding layer with a higher refractive index in the lower cladding layer
Implementation Method 2
a light shielding groove that reaches the absorption layer to absorb stray light
Data Source
AI summary
In a semiconductor laser device, a light shielding groove is formed in an upper cladding layer so as to be adjacent to a bank in a waveguide direction. A surface of the light shielding groove is covered with an insulating layer (not illustrated), and a depth of the light shielding groove reaches an absorption layer that is either a substrate or a buffer layer formed on the substrate.