Semiconductor Laser Diode Shortened Cavity Length Design
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Solution Overview
Problem
Conventional semiconductor laser diodes with edge-emitting type face challenges in achieving high-speed modulation due to limitations in cavity length, which restricts their ability to operate at speeds exceeding 15 GHz, necessitating a solution to shorten the cavity length without compromising device size or production handling.
Innovation Solution
A semiconductor laser diode design featuring a mesa with facets stood back from the substrate edges, allowing for a shortened cavity length while maintaining the device's overall size, facilitating easier handling and enabling higher resonant frequencies and modulation speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the cavity length of the laser diode is shortened to enable high-speed modulation exceeding 15 GHz, then the modulation speed is improved, but the device becomes more difficult to handle during production
Solution Approach 1:
The patent introduces a longitudinal dimension offset between the mesa facets and substrate edges, creating a stepped configuration where the facets are positioned at a different longitudinal coordinate than the edges. This dimensional separation allows the cavity length to be independently controlled without directly reducing the overall device footprint, thereby maintaining ease of handling during production while achieving the required short cavity length for high-speed modulation
2Reliability
If the cavity length is reduced to increase resonant frequency for high-speed operation, then the modulation capability is improved, but the device size reduction complicates manufacturing handling
Solution Approach 1:
The patent segments the device into distinct functional zones: the mesa structure containing the active layer defines the optical cavity, while the substrate provides mechanical support and electrical connections. By decoupling these functions spatially and allowing the mesa facets to be positioned independently from the substrate edges, the design enables short cavity length for high resonant frequency while maintaining adequate device size for manufacturing handling
Solution Approach 2:
The invention utilizes the longitudinal dimension to create an offset configuration where mesa facets are positioned at a different longitudinal coordinate than substrate edges. This dimensional separation allows independent optimization of cavity length for high-speed modulation while maintaining overall device dimensions suitable for manufacturing handling
Data Source
AI summary
A semiconductor laser diode (LD) with a shortened cavity length is disclosed. The LD provides a rectangular substrate and, on the substrate, a cavity structure including a mesa with facets forming the laser cavity. The facets of the mesa are stood back from the side of the substrate. Pads to provide electrical signals are arranged in both sides of the mesa close to the sides of the substrate.