Laser Diode Waveguide Structure for Higher Order Mode Suppression
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Solution Overview
Problem
Conventional laser diodes suffer from higher order mode oscillations in the lateral direction, leading to reduced brightness and output power, as they are unable to effectively suppress these modes while maintaining lower order mode light.
Innovation Solution
A laser diode with a vertical epitaxial structure incorporating a higher order mode suppression layer (HOMSL) adjacent to the lateral waveguide, which can be an absorbing material or an aperiodic structure with different refractive indices, is used to suppress higher order modes by introducing differential loss to these modes compared to lower order modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a broad area laser diode structure is used to increase output power, then the output power increases, but higher order modes are generated that reduce beam quality and brightness
Solution Approach 1:
The patent applies local quality by introducing a higher order mode suppression layer (HOMSL) with specific optical properties at particular locations adjacent to the lateral waveguide. This HOMSL has a refractive index different from the cladding layers, creating localized optical loss that selectively suppresses higher order modes without affecting the fundamental mode, thereby maintaining beam quality while preserving high output power capability
Solution Approach 2:
The patent changes the optical parameters by introducing a layer with different refractive index characteristics (the HOMSL) adjacent to the lateral waveguide. This parameter change creates differential optical loss for different modes, where higher order modes experience greater loss than lower order modes, enabling mode suppression while maintaining the broad area structure for high power output
2Power
If the lateral waveguide width is increased to improve power output, then more power can be extracted, but higher order modes oscillate more strongly
Solution Approach 1:
The HOMSL is positioned locally adjacent to the lateral waveguide where it can selectively interact with higher order modes. This localized structure provides differential loss that stabilizes the mode distribution by suppressing higher order modes while allowing the fundamental mode to dominate, even in broad area lasers with wide lateral waveguides
Solution Approach 2:
The HOMSL acts as an intermediary optical element between the lateral waveguide and the surrounding cladding layers. It mediates the optical field distribution by introducing controlled loss that preferentially affects higher order modes, thereby stabilizing the overall mode composition without directly modifying the lateral waveguide dimensions
3Device complexity
If conventional cladding layers are used without additional suppression structures, then the device complexity remains low, but higher order modes cannot be effectively suppressed
Solution Approach 1:
Rather than redesigning the entire laser structure, the patent introduces a targeted HOMSL with specific optical properties at a localized position adjacent to the lateral waveguide. This minimal structural addition provides higher order mode suppression while maintaining overall device simplicity and avoiding complex redesign of the conventional laser diode architecture
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 configuration enhances the beam parameter product and output power by effectively suppressing higher order modes, thereby improving the brightness and efficiency of the laser diode.
Implementation Method 1
a higher order mode suppression layer (HOMSL) disposed adjacent to at least one lateral side of the lateral waveguide and that extends in a longitudinal direction
Implementation Method 2
an aperiodic structure with different refractive indices
Data Source
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AI summary
A laser diode vertical epitaxial structure, comprising a transverse waveguide comprising an active layer between an n-type semiconductor layer and a p-type semiconductor layer wherein the transverse waveguide is bounded by a lower index n-cladding layer on an n-side of the transverse waveguide and a lower index p-cladding layer on a p-side of the transverse waveguide, a lateral waveguide that is orthogonal to the transverse waveguide, wherein the lateral waveguide is bounded in a longitudinal direction at a first end by a facet coated with a high reflector (HR) coating and at a second end by a facet coated with a partial reflector (PR) coating and a higher order mode suppression layer (HOMSL) disposed adjacent to at least one lateral side of the lateral waveguide and that extends in a longitudinal direction.