VCSEL Mirror Structure for Stable Transverse Mode Emission
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Solution Overview
Problem
Existing vertical cavity surface emitting devices struggle with unstable light emission patterns, particularly in transverse modes, leading to undesirable diffraction effects and reduced output power.
Innovation Solution
The device incorporates a second reflecting mirror with an intermediate dielectric film having a slower etching rate, allowing precise control of mirror loss distribution by partially removing the multilayer films, thereby stabilizing the transverse mode through controlled etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional multilayer film reflecting mirrors are used, then the device structure is simple, but the light emission pattern is unstable and transverse mode control is poor
Solution Approach 1:
The second reflecting mirror is segmented into a first multilayer film and a second multilayer film with different reflectivity characteristics. The first multilayer film has higher reflectivity while the second multilayer film has lower reflectivity, creating distinct functional zones within the mirror structure that enable stable transverse mode control
Solution Approach 2:
Different regions of the reflecting mirror are assigned different optical properties. The first multilayer film region provides high reflectivity for fundamental mode confinement, while the second multilayer film region provides lower reflectivity to suppress higher-order modes, achieving local optimization of mode control
2Reliability
If etching is applied to control mirror loss distribution, then transverse mode stability improves, but manufacturing precision requirements increase
Solution Approach 1:
The intermediate dielectric film is formed beforehand between the first and second multilayer films, serving as a pre-positioned etching stop layer. This preliminary structure guides the subsequent etching process, ensuring that etching stops at the correct depth without requiring extremely precise control, thus reducing manufacturing precision requirements
3Power
If higher order modes are suppressed, then fundamental mode emission is enhanced, but device complexity increases due to additional layers
Solution Approach 1:
An intermediate dielectric film is introduced between the first and second multilayer films of the second reflecting mirror. This intermediate layer acts as a mediator that enables precise control of mirror loss distribution and etching depth, facilitating effective suppression of higher-order modes while maintaining a relatively compact structure
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 ensures stable transverse mode operation, enhancing light emission stability and output power by confining current and light within defined regions, resulting in a unimodal laser beam.
Implementation Method 1
an intermediate dielectric film 19C having a slower etching rate than those of the high refractive index dielectric film H2 and the low refractive index dielectric film L2
Implementation Method 2
a first multilayer film 19A in which the low refractive index dielectric film L2 and the high refractive index dielectric film H2 are stacked in alternation
Data Source
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AI summary
A vertical cavity surface emitting device includes a substrate, a first multilayer film reflecting mirror, a light-emitting structure layer, and a second multilayer film reflecting mirror. The first multilayer film reflecting mirror is formed on the substrate. The light-emitting structure layer is formed on the first multilayer film reflecting mirror. The light-emitting structure layer includes a light-emitting layer. The second multilayer film reflecting mirror is formed on the light-emitting structure layer. The second multilayer film reflecting mirror constitutes a resonator between the first multilayer film reflecting mirror and the second multilayer film reflecting mirror. The second multilayer film reflecting mirror includes a first multilayer film, an intermediate film, and a second multilayer film. The first multilayer film has low refractive index films made of a low refractive index material and high refractive index films made of a high refractive index material having a refractive index higher than a refractive index of the low refractive index material. The low refractive index films and the high refractive index films are alternately stacked. The intermediate film covers an upper surface of the first multilayer film. The intermediate film has a translucency to a light emitted from the light-emitting layer. The second multilayer film is formed to partially cover an upper surface of the intermediate film. The second multilayer film has low refractive index films made of the low refractive index material and high refractive index films made of the high refractive index material. The low refractive index films and the high refractive index films are alternately stacked. The intermediate film has a film thickness based on 1/2 of a wavelength inside the intermediate film of a light emitted from the light-emitting layer.