Stacked VCSEL Gratings for Transverse Mode Confinement
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Solution Overview
Problem
Optical emitters, such as VCSELs, face mode competition issues due to the propagation of undesired modes, which affect optical performance, and existing DBR structures fail to confine these modes in the transverse direction without restricting the oxidation aperture size or shape.
Innovation Solution
A stacked periodic grating structure with a selected period, depth, and fill factor is implemented to achieve greater than a threshold level of optical field confinement in the transverse direction, enabling modal discrimination and suppression of undesired modes, thereby allowing single-transverse-mode operation without limiting the oxidation aperture size or shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional DBR structure is used, then the optical emitter can operate, but undesired modes propagate and degrade optical performance
Solution Approach 1:
The grating structure is divided into multiple stacked periods with alternating high and low refractive index materials, creating discrete layers that work together to achieve mode confinement. Each layer segment contributes to the overall optical path difference required for effective transverse mode discrimination.
Solution Approach 2:
The invention transitions from conventional vertical-only mode control to two-dimensional mode confinement by adding transverse direction control through the periodic grating structure. This enables suppression of undesired transverse modes while maintaining vertical cavity operation.
2Reliability
If the oxidation aperture size is reduced to suppress undesired modes, then mode control improves, but the aperture size and shape are restricted
Solution Approach 1:
The invention adds transverse direction control through periodic gratings, enabling mode suppression without relying solely on aperture size reduction. This dimensional addition allows large aperture areas to maintain single-transverse-mode operation.
Solution Approach 2:
The grating parameters (period, depth, fill factor) are optimized to achieve the desired optical field confinement. By adjusting these parameters, the system achieves mode control with a threshold level of confinement without fixing the aperture size or shape constraints.
3Reliability
If a stacked periodic grating structure is implemented, then transverse mode confinement is achieved, but the device structure becomes more complex
Solution Approach 1:
The grating structure uses alternating layers of high and low refractive index materials (such as AlGaAs and GaAs) to create the periodic structure. This composite approach enables effective optical path difference and mode confinement while using standard semiconductor materials compatible with VCSEL fabrication.
Solution Approach 2:
The invention replaces mechanical aperture restriction with optical path manipulation through refractive index variations. Instead of physically blocking modes with a small aperture, the periodic grating uses optical interference effects to achieve mode confinement.
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 stacked grating structure effectively controls mode propagation in both vertical and transverse directions, enabling single-mode lasing and polarization control, suitable for applications like 3D sensing, without restricting the oxidation aperture size or shape.
Implementation Method 1
The stacked periodic grating structure has a selected period, depth, and fill factor, wherein the selected period, depth, and fill factor of the stacked periodic grating structure are selected to achieve greater than a threshold level of optical field confinement in a transverse direction
Implementation Method 2
a stacked periodic grating structure disposed on the one or more DBRs, wherein the stacked periodic grating structure includes a set of layers
Implementation Method 3
one or more distributed Bragg reflectors (DBRs) disposed on the oxidation aperture
Data Source
AI summary
Some implementations described herein may provide an optical device. The optical device may include an optical emitter and an optical element aligned to the optical emitter. The optical element may include an oxidation aperture, one or more distributed Bragg reflectors (DBRs) disposed on the oxidation aperture, and a stacked periodic grating structure disposed on the one or more DBRs. The stacked periodic grating structure may include a set of layers. The set of layers may include alternating layers of a first material and a second material. The stacked periodic grating structure may have a selected period, depth, and fill factor that are selected to achieve greater than a threshold level of optical field confinement in a transverse direction of an optical field emitted by the optical emitter.