Laser Diode Higher Order Mode Suppression Layer
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Solution Overview
Problem
Conventional laser diodes face challenges in suppressing higher order modes in the lateral direction, leading to reduced brightness and increased divergence angles, which limits their power-scaling and cost-effectiveness in high-power applications.
Innovation Solution
The introduction of a Higher Order Mode Suppression Layer (HOMSL) adjacent to the lateral waveguide, which can be an index guiding, anti-waveguiding, or high loss structure, extending partially along the longitudinal direction to minimize loss for unsuppressed modes while efficiently suppressing higher order modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the stripe width is increased to improve power output, then the output power increases, but the lateral divergence angle increases and brightness decreases
Solution Approach 1:
The patent segments the waveguide structure by introducing a buried layer that divides the lateral confinement region into distinct sections. This segmentation allows different regions to support different mode structures, enabling the fundamental mode to be guided while higher order modes are suppressed, thus maintaining brightness at higher power levels
Solution Approach 2:
The patent applies local quality by creating a buried layer with specific refractive index properties in a localized region beneath the waveguide. This local modification of the optical structure selectively affects higher order modes in the lateral direction while preserving fundamental mode propagation, thereby improving brightness without reducing stripe width
2Illumination intensity
If the stripe width is reduced to improve brightness, then the brightness increases, but the output power decreases
Solution Approach 1:
The segmented waveguide structure with the buried layer enables independent optimization of brightness and power. The segmentation creates regions with different optical properties that can simultaneously support high brightness (through fundamental mode guidance) and high power (through extended stripe width)
Solution Approach 2:
The patent changes the optical parameters of the waveguide structure by introducing the buried layer with specific refractive index characteristics. This parameter change modifies the mode confinement properties, allowing the structure to maintain single-mode operation at larger stripe widths, thus achieving both high brightness and high power
3Illumination intensity
If higher order modes are suppressed by reducing stripe width, then the divergence angle decreases, but the emitter width is reduced
Solution Approach 1:
The buried layer segments the lateral confinement structure, creating distinct optical regions that enable higher order mode suppression without requiring a reduction in overall stripe width. The segmentation allows the emitter to maintain its width while still achieving single-mode operation through the modified waveguide 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 approach enhances the brightness and power efficiency of laser diodes by reducing the slow-axis divergence angle without reducing emitter width, thereby improving the beam parameter product and output power.
Implementation Method 1
A laser diode may include a transverse waveguide and a lateral waveguide... a buried higher order mode suppression layer (HOMSL) disposed beneath the p-cladding within the lateral waveguide
Data Source
AI summary
A laser diode, comprising a transverse waveguide that is orthogonal to the lateral waveguide comprising an active layer between an n-type waveguide layer and a p-type waveguide layer, wherein the transverse waveguide is bounded by an n-type cladding layer on an n-side and p-type cladding layer on a p-side and a lateral waveguide bounded in a longitudinal direction at a first end by a high reflector (HR) coated facet and at a second end by a partial reflector (PR) coated facet, the lateral waveguide further comprising a buried higher order mode suppression layer (HOMSL) disposed beneath the p-cladding within the lateral waveguide or on one or both sides of the lateral waveguide or a combination thereof, wherein the HOMSL extends in a longitudinal direction from the HR facet a length less than the distance between the HR facet and the PR facet.