VCSEL Reflectance Adjustment Layer for High-Output Mode Control
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Solution Overview
Problem
Existing Vertical Cavity Surface Emitting Lasers face challenges in inhibiting high order transverse mode oscillation while achieving high output, as previous technologies like metal electrodes with apertures result in significant light absorption, limiting output to less than 3 mW at 25°C.
Innovation Solution
A Vertical Cavity Surface Emitting Laser design featuring a first and second multilayer film reflector with a reflectance adjustment layer, where the reflectance difference between central and edge regions increases with temperature, effectively inhibiting high order transverse mode oscillation and maintaining high output by distributing basic transverse mode in the central region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal electrode with aperture is provided to inhibit high order transverse mode oscillation, then high order transverse mode oscillation is inhibited, but light absorption by the metal electrode is large and output is limited to less than 3 mW
Solution Approach 1:
A dielectric layer is introduced as an intermediary between the metal electrode and the active layer. This dielectric layer has high reflectance for the laser wavelength and acts as an optical mediator that reflects light back into the cavity without significant absorption, thereby maintaining high output while the metal electrode continues to suppress high order transverse modes through its aperture structure
Solution Approach 2:
The electrode structure is designed as a composite system combining a metal electrode (for transverse mode control) with a dielectric layer (for high reflectance and low absorption). This composite structure integrates the advantages of both materials: the metal provides spatial selectivity for mode suppression while the dielectric ensures efficient light reflection and minimal loss
2Reliability
If reflectance of the second multilayer film reflector is increased to inhibit high order transverse mode oscillation at high temperature, then high order transverse mode oscillation is inhibited, but basic transverse mode oscillation is also affected and output decreases
Solution Approach 1:
The reflectance adjustment layer is designed with spatially varying reflectance properties: it provides high reflectance in the peripheral region to suppress high order transverse modes while maintaining lower reflectance in the central region to preserve basic transverse mode oscillation. This local differentiation of optical properties allows selective mode control without compromising overall output
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 design effectively inhibits high order transverse mode oscillation at high temperatures while maintaining high output, with the basic transverse mode being minimally affected by reflectance changes, and reduces threshold current at elevated temperatures.
Implementation Method 1
The light is reflected by a pair of multilayer film reflectors, laser oscillation is generated in a given wavelength
Implementation Method 2
the reflectance difference ΔR(=Rx−Ry) between reflectance Rx in a region opposed to a central region of the light emission region and reflectance Ry in a region opposed to an outer edge region of the light emission region is increased associated with temperature increase from ambient temperature to high temperature
Data Source
AI summary
The present invention provides a Vertical Cavity Surface Emitting Laser including: a first multilayer film reflector; an active layer having a light emission region; a second multilayer film reflector; and a reflectance adjustment layer in this order on a substrate side. The first multilayer film reflector and the second multilayer film reflector have a laminated structure in which reflectance of oscillation wavelength λx is almost constant without depending on temperature change. The active layer is made of a material with which a maximum gain is obtained at temperature higher than ambient temperature. The reflectance adjustment layer has a laminated structure in which difference ΔR(=Rx−Ry) between reflectance Rx of a region opposed to a central region of the light emission region and reflectance Ry of a region opposed to an outer edge region of the light emission region is increased associated with temperature increase from ambient temperature to high temperature.