Shortened Semiconductor Laser Resonator for High-Speed Modulation
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Solution Overview
Problem
Existing semiconductor laser devices face challenges in achieving high-speed modulation while maintaining manageable chip size and cleavage, as shortening the resonator length complicates handling and increases manufacturing costs due to integrated transparent waveguides.
Innovation Solution
A semiconductor laser device with a resonator unit having a shorter length than the semiconductor substrate, featuring a diffraction grating, inverted or forward mesa slope facets, anti-reflection and reflective coatings, and a metal mirror for efficient light emission and reflection, along with a manufacturing method that includes selective growth and etching to form these features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the resonator length is shortened to increase relaxation oscillation frequency for high-speed modulation, then the modulation speed is improved, but chip handling and cleavage become difficult
Solution Approach 1:
The invention divides the semiconductor laser structure into two distinct parts: a short resonator unit containing the active layer and diffraction grating for high-speed modulation, and a longer semiconductor substrate that provides mechanical stability and ease of handling. This segmentation allows the resonator length to be shortened for improved modulation speed while the substrate length maintains handling convenience.
2Speed
If the resonator length is shortened to improve modulation speed, then the relaxation oscillation frequency increases, but manufacturing cost increases due to integrated transparent waveguides
Solution Approach 1:
The invention extracts the resonator unit from the semiconductor substrate, creating a separate, integrated structure. The resonator unit is formed by selective growth on the substrate and includes the active layer and diffraction grating. This extraction allows the resonator to be optimized for high-speed operation while avoiding the need for complex integrated transparent waveguide structures, thereby reducing manufacturing costs.
3Speed
If the resonator length is shortened to increase modulation speed, then the relaxation oscillation frequency increases, but the number of crystal growth steps increases
Solution Approach 1:
The invention merges the formation of the resonator unit with the semiconductor substrate manufacturing process. The resonator unit is created through selective growth directly on the substrate in an integrated manner, combining multiple functions (substrate support, resonator structure, and optical waveguide) into a unified growth process, thereby reducing the total number of separate crystal growth steps.
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
Facilitates easier handling and cleavage, increases relaxation oscillation frequency for high-speed modulation, reduces manufacturing costs by minimizing the need for transparent waveguides, and suppresses light scattering loss with smooth crystal surfaces.
Implementation Method 1
a diffraction grating, wherein the diffraction grating is formed on or underneath the active layer
Implementation Method 2
an anti-reflection coating film formed on the front facet
Implementation Method 3
a reflective film formed on the rear facet
Data Source
AI summary
A semiconductor laser device includes a semiconductor substrate, a resonator unit formed on the semiconductor substrate and having an active layer, a diffraction grating formed on or underneath the active layer, a front facet of an inverted mesa slope, and a rear facet, an anti-reflection coating film formed on the front facet, a reflective film formed on the rear facet, an upper electrode formed on the resonator unit, and a lower electrode formed underneath the semiconductor substrate, wherein a length in a resonator direction of the resonator unit is shorter than a length in the resonator direction of the semiconductor substrate, and a laser beam is emitted from the front facet.