Surface-Emitting Laser Optical Element with Photodetector
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Solution Overview
Problem
The photodetector element in optical modules using surface-emitting type semiconductor lasers can influence the optical characteristics of the lasers, particularly due to temperature dependency and the need for precise alignment, which affects light output monitoring and miniaturization.
Innovation Solution
The optical element incorporates a photodetector element with a semiconductor layer having a specific film thickness that satisfies certain mathematical conditions relative to the designed wavelength and refractive index, positioned above the emission surface of the surface-emitting type semiconductor laser, to minimize interference with the laser's optical characteristics, including the use of an isolation layer and specific electrode configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a photodetector element is provided on top of a surface-emitting type semiconductor laser to monitor light output, then miniaturization of the optical element and reduction of alignment cost can be achieved, but the photodetector element may influence the optical characteristics of the semiconductor laser
Solution Approach 1:
The patent applies parameter changes by precisely controlling the film thickness of the semiconductor layer in the photodetector element to satisfy specific mathematical formulas (d = (2m-1)λ/4n - 3λ/16n or d = (2m-1)λ/4n + 3λ/16n where m is an integer, n is refractive index, and λ is the designed wavelength). This parameter optimization ensures that the photodetector monitors light output effectively while minimizing its influence on the semiconductor laser's optical characteristics, thus resolving the contradiction between miniaturization and optical stability.
2Reliability
If the semiconductor layer film thickness is optimized to suppress photodetector influence on laser characteristics, then optical stability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for the semiconductor layer thickness using mathematical formulas that account for the refractive index and wavelength. By providing these explicit parameter specifications, the patent balances the need for optical stability with manufacturability, as the formulas give clear guidance for fabrication while ensuring the photodetector's minimal impact on laser characteristics.
Solution Approach 2:
The patent introduces an isolation layer between the semiconductor laser and the photodetector element. This intermediary structure helps to further reduce the influence of the photodetector on the laser's optical characteristics, making it easier to achieve optical stability without requiring extremely tight film thickness control, thus mediating between reliability and manufacturing precision 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
This configuration reduces the impact of the photodetector on the surface-emitting type semiconductor laser's optical characteristics, stabilizes light divergence angles, and maintains efficient light confinement, thereby improving the stability and miniaturization of optical elements and modules.
Implementation Method 1
a film thickness by which a designed wavelength of light of the surface-emitting type semiconductor laser does not coincide with a center wavelength of Fabry-Perot resonance of the semiconductor layers
Implementation Method 2
the photodetector element includes a semiconductor layer having a photoabsorption layer
Data Source
AI summary
An optical element comprising: a surface-emitting type semiconductor laser having an emission surface; and a photodetector element formed above the emission surface of the surface-emitting type semiconductor laser, wherein the photodetector element includes a semiconductor layer having a photoabsorption layer, the semiconductor layer having a film thickness d that satisfies a formula (1) as follows:(2m−1)λ/4n−3λ/16n<d<(2m−1)λ/4n+3λ/16n . . . , (1)where m is an integer, n is a refractive index of the semiconductor layer, and λ is a designed wavelength of the surface-emitting type semiconductor laser.