VCSEL Surface-Trapped Mode for Single-Mode Operation
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Solution Overview
Problem
Conventional light-emitting devices, such as VCSELs, face challenges in maintaining single-mode operation as the aperture size increases, leading to multimode operation and complex optical systems that are bulky and expensive, making efficient coupling to single-mode fibers difficult.
Innovation Solution
The implementation of a surface-trapped TM-polarized optical mode between a distributed Bragg reflector and a homogeneous medium, with selective chemical transformation forming a central core and periphery having different refractive index profiles, allowing the longitudinal VCSEL mode to be non-orthogonal to the surface-trapped mode, enabling efficient lateral leakage and transformation between modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the aperture size of VCSEL is increased to achieve higher output power, then the power increases, but the device transitions from single-mode to multimode operation
Solution Approach 1:
The patent applies local quality by creating an oxide-confined aperture structure where the refractive index varies spatially - the oxidized region has different optical properties than the non-oxidized region. This local variation in optical quality allows the device to maintain single-mode operation in the center while permitting larger overall aperture size for higher power output.
Solution Approach 2:
The oxide layer acts as an intermediary structure that mediates between the need for large aperture (high power) and single-mode operation. The oxide-confined aperture creates a refractive index profile that guides the fundamental mode while suppressing higher-order modes, enabling the aperture to serve dual purposes.
2Reliability
If external resonators are added to achieve single-mode lasing in large aperture devices, then single-mode operation is achieved, but the device becomes bulky and expensive
Solution Approach 1:
The patent extracts the resonator function from external optical components and integrates it into the semiconductor structure itself through the oxide-confined aperture. The refractive index profile created by selective oxidation provides the necessary mode confinement without requiring external resonators, simplifying the device.
Solution Approach 2:
The patent merges the aperture function and the resonator function into a single integrated structure. The oxide-confined aperture simultaneously serves as the current confinement region and the optical resonator, eliminating the need for separate external resonator components.
3Power
If multiple lasers on a single wafer are used to achieve high single-mode power, then the power increases, but the beam cannot be focused to a small spot
Solution Approach 1:
The patent segments the aperture into a central non-oxidized region and an surrounding oxidized region. This segmentation creates distinct optical zones where the central region supports single-mode operation while the overall structure maintains large aperture area for high power, producing a clean single-mode beam that can be focused.
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 approach facilitates the fabrication of single transverse mode VCSELs and integrated optical circuits with enhanced optical amplification and beam steering capabilities, reducing optical losses and enabling efficient coupling to planar waveguides.
Implementation Method 1
surface-trapped TM-polarized optical mode existing at a boundary between a distributed Bragg reflector and a homogeneous medium
Implementation Method 2
surface-trapped TM-polarized optical mode
Implementation Method 3
Selective chemical transformation, like selective oxidation, etching or alloy composition intermixing form a central core and a periphery having different vertical profiles of the refractive index
Implementation Method 4
resonant optical cavity surrounded by two DBRs
Implementation Method 5
distributed Bragg reflector surrounded by two DBRs
Data Source
AI summary
An optoelectronic device employs a surface-trapped TM-polarized optical mode existing at a boundary between a distributed Bragg reflector (DBR) and a homogeneous medium, dielectric or air. The device contains a resonant optical cavity surrounded by two DBRs, and an additional DBR section on top supporting the surface-trapped mode. Selective chemical transformation, like selective oxidation, etching or alloy composition intermixing form a central core and a periphery having different vertical profiles of the refractive index. Therefore, the longitudinal VCSEL mode in the core is non-orthogonal to the surface-trapped mode in the periphery, and the two modes can be transformed into each other. Such transformation allows fabrication of a number of optoelectronic devices and systems like a single transverse mode VCSEL, an integrated optical circuit operating as an optical amplifier, an integrated optical circuit combining a VCSEL and a resonant cavity photodetector, etc.