Surface-Emitting Laser Wavelength Control via Selective Etching
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Solution Overview
Problem
Current techniques face challenges in forming surface-emitting laser elements with narrow wavelength intervals, particularly for atomic clocks, due to difficulties in achieving uniform and thin film thicknesses for wavelength adjustment layers, which affects the precision of the oscillation wavelength.
Innovation Solution
The surface-emitting laser element is designed with a wavelength adjustment layer composed of different semiconductor materials (GaInP and GaAsP) where the thickness is adjusted by selective etching using specific etching fluids, allowing for precise control of the wavelength adjustment layer thickness and achieving multiple surface-emitting lasers with different wavelengths on a single chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a wavelength adjustment layer with uniform and thin film thickness is formed to achieve narrow wavelength intervals, then the precision of oscillation wavelength is improved, but the manufacturing difficulty increases due to dispersion of growth rate and irregularity in film thickness distribution
Solution Approach 1:
The wavelength adjustment layer is divided into multiple sub-layers with different materials (GaInP and GaAsP) that can be selectively etched. This segmentation allows independent control of each sub-layer's thickness through selective etching processes, avoiding the need to form the entire layer with uniform thin thickness in a single step, thus resolving the contradiction between wavelength precision and manufacturing difficulty
Solution Approach 2:
The patent changes the material composition parameter of the wavelength adjustment layer by using alternating layers of GaInP and GaAsP with different etching characteristics. This parameter change enables selective etching to precisely control the final thickness, transforming the manufacturing approach from direct thin-film formation to controlled material removal, thereby improving manufacturability while maintaining precision
2Productivity
If multiple surface-emitting lasers with different wavelengths are formed on a single chip, then the integration density and productivity are improved, but the device complexity increases due to the need for precise wavelength control
Solution Approach 1:
Different regions of the chip are assigned different wavelength adjustment layer configurations (different numbers of GaInP and GaAsP layers, different etching depths) to achieve different wavelengths. This local quality approach allows each laser element to have its specific wavelength characteristics while maintaining a unified manufacturing process across the entire chip, thus increasing integration density without proportionally increasing control complexity
Solution Approach 2:
The alternating GaInP/GaAsP layer structure serves multiple functions simultaneously: it acts as the wavelength adjustment layer, provides etching selectivity for precise thickness control, and enables wavelength differentiation across multiple devices. This multi-functionality reduces the need for separate control mechanisms for each wavelength, thereby improving productivity while managing device complexity
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 production of surface-emitting lasers with accurate and stable wavelength intervals, improving the precision of the oscillation wavelength and reducing the deviation between lasers, making them suitable for high-performance applications like atomic clocks.
Implementation Method 1
removing such a wavelength adjustment layer one-by-one for each surface-emitting laser by means of wet-etching to change a thickness of the wavelength adjustment layer
Data Source
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AI summary
Disclosed is a surface-emitting laser element including a semiconductor substrate and plural surface-emitting lasers configured to emit light with mutually different wavelengths, each surface-emitting laser including a lower Bragg reflector provided on the semiconductor substrate, a resonator provided on the lower Bragg reflector, an upper Bragg reflector provided on the resonator, and a wavelength adjustment layer provided in the upper Bragg reflector or lower Bragg reflector, the wavelength adjustment layers included in the surface-emitting lasers having mutually different thicknesses, at least one of the wavelength adjustment layers including adjustment layers made of two kinds of materials, and numbers of the adjustment layers included in the wavelength adjustment layers being mutually different.