Surface-Emitting Laser Polarization Control With Anisotropic Layer
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Solution Overview
Problem
Surface emitting lasers face challenges in achieving stable polarization of laser light due to the high optical absorption of p-type semiconductor materials, leading to increased threshold current, decreased external quantum efficiency, and poor temperature characteristics, as well as difficulties in controlling the polarization direction.
Innovation Solution
The surface emitting laser device incorporates a substrate with a lower reflecting mirror and an active layer, featuring an upper reflecting mirror formed by alternately laminating dielectrics and a semiconductor adjusting layer with shape anisotropy in two perpendicular directions, allowing for stable polarization of laser light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a p-type semiconductor layer is used for the light wave guide region, then the device can be manufactured with conventional semiconductor materials, but the threshold current increases, external quantum efficiency decreases, and temperature characteristics degrade
Solution Approach 1:
The patent extracts the p-type semiconductor layer from the light wave guide region, removing the harmful element (p-type material with high optical absorption) while maintaining the overall device structure. This allows the light wave guide to be formed by other means (such as the resonator structure itself) while the p-type material is retained only where necessary for electrical contact.
Solution Approach 2:
The patent introduces an n-type semiconductor layer as an intermediary between the active layer and the p-type contact layer. This n-type layer serves as a mediator that allows current injection while preventing the p-type material from being in direct contact with the light wave guide region, thus avoiding the harmful optical absorption effects.
2Volume of moving object
If a surface emitting laser structure is used, then integration and miniaturization are enabled, but controlling the polarization direction becomes difficult
Solution Approach 1:
The patent introduces asymmetric stress through a stress layer with different thermal expansion coefficients than the surrounding materials. This asymmetric stress distribution in the light wave guide region creates preferential refractive index changes that favor one polarization direction, thereby controlling the output polarization without requiring complex external components.
Solution Approach 2:
The patent utilizes temperature-dependent parameters by employing materials with different thermal expansion coefficients. The stress layer's thermal expansion properties change with temperature, inducing controlled stress and refractive index changes that affect the polarization characteristics of the laser output, enabling polarization control through temperature management.
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 configuration enables the emission of laser light with stable polarization in a predetermined direction, improving the performance and controllability of the surface emitting laser device.
Implementation Method 1
The upper reflecting mirror is formed by alternately laminating dielectrics, refracting indices of the dielectrics being different from each other
Implementation Method 2
upper reflecting mirror being formed by alternately laminating dielectrics, refracting indices of the dielectrics being different from each other
Implementation Method 3
an adjusting layer formed of semiconductor, provided in an emitting region between the active layer and the upper reflecting mirror, laser light being emitted from the emitting region. A shape of the adjusting layer in a plane parallel to a surface of the substrate has shape anisotropy in two mutually perpendicular directions
Data Source
AI summary
Disclosed is a surface emitting laser device, including a substrate; a lower reflecting mirror provided on the substrate; an active layer provided on the lower reflecting mirror; an upper reflecting mirror provided on the active layer, including an emitting region, laser light being emitted from the emitting region, the upper reflecting mirror being formed by alternately laminating dielectrics, refracting indices of the dielectrics being different from each other; and an adjusting layer formed of semiconductor, provided in the emitting region between the active layer and the upper reflecting mirror, a shape of the adjusting layer in a plane parallel to a surface of the substrate including shape anisotropy in two mutually perpendicular directions.