Semiconductor Laser Absorber Layer Reduces Stray Radiation
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Solution Overview
Problem
The uncontrolled coupling of radiation emitted by the rear laser mirror into the usable light beam degrades the coherence properties and detection sensitivity of semiconductor lasers, particularly in applications like gas sensors where narrow linewidth and precise emission wavelength are crucial.
Innovation Solution
A semiconductor laser with a layer of absorbing material or an absorber module positioned on the semiconductor substrate behind the rear laser mirror to absorb and convert radiation into heat, reducing the number of photons that can couple into the usable light beam as scattered light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the rear laser mirror is coated to reduce light emission, then energy loss is reduced, but some radiation (at least a few percent) still emits through the rear mirror degrading coherence properties
Solution Approach 1:
An absorber layer is introduced as an intermediary component between the rear laser mirror and the external environment. This absorber layer specifically targets and absorbs the residual radiation that penetrates through the rear mirror coating, preventing it from degrading the coherence properties of the laser beam while maintaining the energy-efficient reflective coating on the rear mirror.
Solution Approach 2:
The solution ensures continuous suppression of harmful radiation by combining the rear mirror's reflective action with the absorber layer's absorptive action. The reflective coating continuously reflects the majority of light to minimize energy loss, while the absorber layer continuously absorbs the residual transmitted radiation, ensuring ongoing protection of coherence properties throughout laser operation.
2Reliability
If an absorber layer is added to the rear laser mirror, then coherence properties are maintained, but device complexity increases
Solution Approach 1:
The absorber layer is merged with the rear laser mirror structure, forming an integrated composite component. Rather than being a separate external element, the absorber layer is directly applied to or integrated with the rear mirror surface, combining the reflective and absorptive functions into a single unified structure that minimizes additional complexity.
Solution Approach 2:
The rear laser mirror is transformed into a composite structure combining a reflective coating layer and an absorber layer. This composite material approach allows the single component to simultaneously perform both reflection (for energy efficiency) and absorption (for coherence protection), reducing the need for multiple separate parts and simplifying the overall device architecture.
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 solution effectively suppresses radiation from the rear laser mirror, maintaining the coherence properties of the light beam and enhancing detection sensitivity in sensor applications by minimizing scattered light, thereby improving the overall efficiency and reliability of semiconductor lasers.
Implementation Method 1
a layer of absorbing material which is arranged at a distance from the laser mirror in the direction of the generated radiation and which is suitable behind the layer of absorbing material to reduce a slope of the light output-current characteristic
Data Source
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AI summary
The invention relates to a semiconductor laser having at least one semiconductor substrate (10), at least one active layer (20) arranged on the semiconductor substrate (10) which generates radiation in a wavelength region, at least one laser mirror (40) which is applied at one end of the active layer (20) perpendicular thereto, through which a part of the radiation generated in the active layer (20) emerges, and which is provided with a layer of absorbing material (50, 60) said layer being suitable for reducing a gradient of the luminous-power/current characteristic for radiation emerging through the laser mirror (40).