Multi-wavelength Semiconductor Laser Window Region Design
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Solution Overview
Problem
Conventional multi-wavelength semiconductor lasers face challenges in achieving high-power operation for high-speed recording on DVDs and CD-Rs due to limitations in optical output and reliability, with AR/HR coatings failing to secure long-term reliability and causing Catastrophic Optical Damage (COD) due to increased power consumption and heat generation.
Innovation Solution
A multi-wavelength semiconductor laser with a window structure formed by diffusing impurities in the active layer, creating a disordered window region with a larger band gap than the gain section, which acts as a transparent region to prevent laser light absorption and reduce COD, allowing for stable high-power operation and optimized far-field pattern for improved light use efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If AR/HR coatings are applied to increase optical output for high-speed recording, then power consumption increases and heat generation increases, but this leads to Catastrophic Optical Damage (COD) and reduces reliability
Solution Approach 1:
The active layer is segmented into a gain section and a window section along the light propagation direction. The gain section generates laser light while the window section acts as a transparent region with larger band gap that prevents absorption of laser light, thereby reducing heat generation and preventing COD while maintaining high optical output
Solution Approach 2:
Different sections of the active layer are given different local qualities: the gain section has properties optimized for light generation while the window section has a larger band gap (achieved by adjusting composition ratios of AlInGaP) to be transparent to laser light. This local differentiation allows high power operation without COD
2Reliability
If the window region length is increased to prevent COD, then the far-field pattern size changes, but this affects light use efficiency in optical systems
Solution Approach 1:
The length of the window section is precisely controlled within specific ranges (5-20 μm for red laser, 3-10 μm for infrared laser) to optimize both COD prevention and far-field pattern characteristics. By adjusting this parameter, the invention achieves reliable high-power operation while maintaining appropriate beam divergence for optical system efficiency
3Stability of the object's composition
If different window region lengths are set for each semiconductor laser wavelength, then far-field pattern stability is achieved, but this increases device complexity
Solution Approach 1:
Multiple semiconductor lasers with different wavelengths (red and infrared) are monolithically integrated on a single GaAs substrate with their respective window sections formed in the same active layer. This merging approach allows different window lengths to be precisely controlled for each wavelength while simplifying manufacturing compared to separate devices
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
The solution stabilizes the far-field pattern size for each wavelength, enhancing light use efficiency in optical systems and preventing COD, enabling reliable high-speed recording capabilities by setting appropriate window region lengths for each semiconductor laser.
Implementation Method 1
creating a disordered window region with a larger band gap than the gain section, which acts as a transparent region to prevent laser light absorption
Implementation Method 2
A multi-wavelength semiconductor laser with a window structure formed by diffusing impurities in the active layer
Data Source
AI summary
Semiconductor lasers for respective wavelengths have window regions with different lengths so as to obtain optimum FFPs for emitted light of the respective wavelengths, and thus dependence on optical output can be equal between the wavelengths, facilitating the design of an optical system.