Surface-Emitting Laser Wavelength Tuning via Layered Material Composition
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Solution Overview
Problem
The variability in growth rates and uniformity of semiconductor layers during the fabrication of surface-emitting lasers makes it difficult to produce large quantities with consistent wavelength, leading to high fabrication costs and low yield rates due to the requirement for precise thickness uniformity of ±1 nm.
Innovation Solution
A surface-emitting laser element with a wavelength-adjusting layer composed of alternately layered GaInP and GaAsP or GaAs, allowing for the emission of laser beams with different wavelengths by adjusting the thickness of this layer, and an atomic oscillator that uses these lasers to control oscillation frequency through quantum interference effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of semiconductor layers is controlled with high precision (±1 nm) to achieve consistent wavelength, then wavelength uniformity is improved, but fabrication cost increases and yield rate decreases
Solution Approach 1:
The patent changes the material composition parameter of the semiconductor layer (varying InGaAsP composition ratios) to adjust the refractive index and optical path length, thereby controlling the oscillation wavelength without requiring extremely precise thickness control. This allows wavelength tuning while maintaining relaxed fabrication tolerances and improving yield rates.
Solution Approach 2:
The patent uses composite semiconductor structures with different material compositions (InGaAsP layers with varying indium and phosphorus ratios) to achieve wavelength control. By combining materials with different optical properties in a layered structure, the oscillation wavelength can be precisely controlled through composition rather than solely through thickness, reducing fabrication difficulty.
2Manufacturing precision
If the thickness of semiconductor layers is controlled with high precision (±1 nm) to achieve consistent wavelength, then wavelength uniformity is improved, but productivity decreases
Solution Approach 1:
The patent changes the material composition parameter (InGaAsP composition ratios) to control optical properties, replacing the need for extreme thickness precision. This parameter substitution allows standard fabrication processes to produce lasers with consistent wavelengths, significantly improving yield rates and productivity.
3Adaptability or versatility
If multiple surface-emitting lasers with different wavelengths are fabricated on the same chip, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent divides the chip into multiple independent laser regions, each with its own wavelength-adjusting layer having different material compositions. This segmentation allows each laser to be independently optimized for a specific wavelength while sharing common fabrication processes and packaging, achieving wavelength variety without excessive complexity.
Solution Approach 2:
The patent creates a universal chip structure that can produce multiple wavelengths by varying only the material composition of the wavelength-adjusting layer while keeping the overall device architecture identical. This multi-functional approach allows a single chip design to serve multiple wavelength applications without requiring different device structures.
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 approach enables the fabrication of surface-emitting lasers with desired wavelengths at a lower cost by selecting from a set of lasers with varying wavelengths, improving reproducibility and reducing fabrication costs while maintaining high wavelength accuracy.
Implementation Method 1
a wavelength-adjusting layer formed above the active layer... the wavelength-adjusting layer includes one of a first film having alternately layered GaInP and GaAsP and a second film having alternately layered GaInP and GaAs
Implementation Method 2
a coherent population trapping (CPT) based atomic clock... modulates the laser beam and simultaneously transitions and excites two electrons in alkali metal atoms with sidebands appearing two sides of a carrier wave having a specific wavelength. The transition energy remains unchanged. When wavelengths of the sidebands match the wavelength of the transition energy, a clearing response that reduces optical absorption in the alikali metal may occur.
Data Source
AI summary
A disclosed surface-emitting laser element includes a lower DBR formed on a substrate, an active layer formed on the lower DBR, an upper DBR formed on the active layer, a wavelength-adjusting layer formed above the active layer, and a plurality of surface-emitting lasers configured to emit respective laser beams having different wavelengths by changing a thickness of the wavelength-adjusting layer. In the surface-emitting laser element, the wavelength-adjusting layer includes one of a first film having alternately layered GaInP and GaAsP and a second film having alternately layered GaInP and GaAs, the thickness of the wavelength-adjusting layer being changed by partially removing each of the alternating layers of a corresponding one of the first and second films.