Edge-Emitting Semiconductor Laser Wavelength Stabilization
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Solution Overview
Problem
Conventional semiconductor lasers experience significant wavelength deviation due to temperature changes, limiting transmission distance, and existing solutions like DFB-LD and DBR-LD have complex structures that reduce productivity and yield.
Innovation Solution
An edge-emitting semiconductor laser with a Bragg reflector composed of alternately layered low- and high-refractive-index layers, each thicker than λ/4n, is introduced between the active layer and light absorption layer to inhibit wavelength deviation without compromising manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a distributed feedback laser (DFB-LD) having a diffraction grating is used to inhibit wavelength deviation, then wavelength stability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the thickness parameter of the semiconductor layers in the Bragg reflector to be greater than λ/4n, which modifies the optical path length and enhances wavelength selectivity. This parameter adjustment allows the reflector to provide strong wavelength stabilization without requiring complex diffraction gratings, thus resolving the contradiction between reliability and device complexity
Solution Approach 2:
The patent introduces a light absorption layer as an intermediary component between the active layer and the Bragg reflector. This intermediary layer absorbs unwanted wavelengths and modes, enhancing the overall wavelength stability while keeping the Bragg reflector structure relatively simple, thereby addressing the contradiction between reliability improvement and device complexity
2Manufacturing precision
If a Bragg reflector with layer thickness > λ/4n is used to provide wavelength selectivity, then manufacturing precision requirements are reduced, but the reflector structure becomes more complex
Solution Approach 1:
The patent deliberately sets the layer thickness parameter to be greater than the conventional λ/4n value, which relaxes the manufacturing precision requirements. This parameter change makes the Bragg reflector easier to manufacture with standard precision equipment while still providing effective wavelength selectivity, thus resolving the contradiction between manufacturing precision and device complexity
3Productivity
If conventional semiconductor lasers are used without wavelength stabilization, then productivity and yield are maintained, but transmission distance is limited due to wavelength deviation
Solution Approach 1:
The patent segments the laser structure into distinct functional layers including the active layer, light absorption layer, and Bragg reflector with multiple alternating layers. This segmentation allows each layer to perform its specific function efficiently while maintaining overall manufacturing simplicity, thus resolving the contradiction between productivity and reliability by enabling wavelength stabilization without compromising manufacturing efficiency
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 design provides wavelength selectivity and stabilizes the lasing wavelength against temperature changes, maintaining high productivity and yield by maximizing reflectance at the desired wavelength, thus extending transmission distance.
Implementation Method 1
a Bragg reflector formed on the active layer and in which low-refractive-index layers and high-refractive-index layers each having a thickness larger than λ/4n are alternately laid one on another
Implementation Method 2
Bragg reflector... providing wavelength selectivity and stabilizes the lasing wavelength... by maximizing reflectance at the desired wavelength
Implementation Method 3
The interface between a semiconductor laser facet and air which is an emergence medium acts as a reflecting mirror... Part of light having propagated through the waveguide exits to the outside through one of the semiconductor facets... The other part of the light is reflected by the facet to again propagate in the waveguide
Implementation Method 4
Light is guided and propagated while being repeatedly reflected totally at the interfaces between the core layer having a high refractive index and the cladding layers having a low refractive index
Implementation Method 5
The light is given a gain and amplified during passage through the active layer... When the sum of the internal loss during propagation in the waveguide and the mirror loss at the time of facet reflection and the gain obtained during propagation become equal to each other, the laser oscillates to emit coherent light from the facet
Data Source
AI summary
An edge-emitting semiconductor laser includes: a semiconductor substrate; a first cladding layer having a first refractive index and formed on the semiconductor substrate; an active layer formed on the first cladding layer and having a second refractive index higher than the first refractive index; a Bragg reflector formed on the active layer and in which low-refractive-index layers and high-refractive-index layers each having a thickness larger than λ/4n are alternately laid one on another where λ is an lasing wavelength and n is a refractive index of a medium; a light absorption layer formed on the Bragg reflector and having bandgap energy lower than that of the active layer; and a second cladding layer formed on the light absorption layer and having a third refractive index lower than the second refractive index.