GaN Vertical Cavity Emitter With Concave Reflector for Single-Mode Output
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Solution Overview
Problem
Vertical cavity-type semiconductor lasers exhibit low luminous efficiency and struggle to emit light in a stable single mode due to multimode transverse emission.
Innovation Solution
A vertical cavity light-emitting element with a gallium-nitride-based semiconductor substrate, multilayer reflectors, and a current confinement structure that concentrates current in a specific region of the active layer, utilizing a reflective structure with a concave reflecting surface to enhance light confinement and control the transverse mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a vertical cavity-type semiconductor laser is used, then the device structure is compact and suitable for integration, but the luminous efficiency is low and the transverse mode stability is poor
Solution Approach 1:
The patent introduces a concave reflective structure with a curved reflecting surface that extends laterally from the lower surface of the semiconductor substrate. This curvature modifies the optical path and light distribution within the vertical cavity, improving light confinement and reducing spatial hole burning effects, thereby enhancing both luminous efficiency and transverse mode stability
Solution Approach 2:
The reflective structure extends in the lateral dimension from the lower substrate surface, creating a three-dimensional optical confinement geometry. This additional spatial dimension provides superior light control compared to conventional planar mirrors, enabling stable single-mode operation while maintaining vertical cavity compactness
2Ease of manufacture
If a conventional vertical cavity structure is used, then the device is simple to manufacture, but the light emission is multimode and luminous efficiency is low
Solution Approach 1:
The concave reflective structure serves multiple functions simultaneously: it acts as a mirror for optical feedback, provides lateral light confinement, modifies the optical mode distribution, and reduces spatial hole burning. This multi-functionality achieves improved luminous efficiency without adding separate components, maintaining fabrication simplicity
3Productivity
If the current confinement structure is added to concentrate current, then the luminous efficiency improves, but the device complexity increases
Solution Approach 1:
The current confinement structure is integrated with the vertical cavity and concave reflective structure to form a unified device architecture. The current confinement region is positioned within the optical cavity, merging electrical and optical functions into a compact structure that improves luminous efficiency without proportionally increasing device complexity
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 achieves high luminous efficiency and stable single-mode light emission with increased output, reducing spatial hole burning and maintaining a Gaussian light intensity distribution.
Implementation Method 1
The reflective structure has a concave reflecting surface that extends to an outside of the one region in a top view and is opposed to the first multilayer reflector
Implementation Method 2
The current confinement structure is formed between the first multilayer reflector and the second multilayer reflector to concentrate a current in one region of the active layer
Implementation Method 3
a semiconductor layer that emits light by application of voltage
Implementation Method 4
an optical resonator is formed by opposing reflectors... light emitted from the semiconductor layer resonates in the optical resonator, generating laser light
Data Source
AI summary
A vertical cavity light-emitting element includes a first multilayer reflector, a semiconductor structure layer, a second multilayer reflector, and a current confinement structure. The current confinement structure concentrates a current in one region of an active layer of the semiconductor structure layer. The vertical cavity light-emitting element has a concave reflective structure disposed on a lower surface of a gallium-nitride-based semiconductor substrate or in a region below the lower surface. The concave reflective structure has a concave reflecting surface that extends to an outside of the one region in a top view viewed in a direction perpendicular to an upper surface of the gallium-nitride-based semiconductor substrate and is opposed to the first multilayer reflector.