Large-Mode Single-Mode Laser Using Threshold-Selective Grating
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Solution Overview
Problem
Current single-mode lasers often fail to achieve high optical powers while maintaining single-mode operation, as they either produce low optical modes or become multimode when attempting to increase waveguide thickness for larger modes.
Innovation Solution
The design incorporates a waveguide configured to support both a fundamental and higher order optical modes, with an active region and grating positioned to reduce the lasing threshold for the fundamental mode while increasing the threshold for higher order modes, using a method that adjusts the positions of these components to maximize the overlap with the fundamental mode and minimize it with higher order modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the waveguide thickness is increased to support larger optical modes, then the optical mode size increases, but the laser becomes multimode operation
Solution Approach 1:
The patent applies local quality by creating different refractive index regions within the waveguide structure. Specifically, it uses a core layer with higher refractive index surrounded by cladding layers with lower refractive indices, forming localized regions with different optical properties. This allows the waveguide to support larger mode sizes while maintaining single-mode operation through controlled local refractive index variations that confine the fundamental mode while suppressing higher-order modes.
Solution Approach 2:
The patent employs parameter changes by systematically varying the thicknesses of different waveguide layers (core layer, first cladding layer, second cladding layer) and their refractive indices to achieve single-mode operation with large mode size. By adjusting these geometric and optical parameters, the waveguide can be designed to support only the fundamental mode while maintaining a large effective mode area, thus resolving the contradiction between mode size and single-mode operation.
2Power
If the waveguide thickness is increased for larger modes, then the optical power increases, but higher order modes are also supported
Solution Approach 1:
The patent extends the waveguide structure from a simple planar configuration to a multi-layered vertical structure with core layer, first cladding layer, and second cladding layer. By adding the vertical dimension with controlled layer thicknesses and refractive indices, the waveguide can achieve large mode size and high optical power while maintaining single-mode operation through the three-dimensional confinement of the fundamental mode and suppression of higher-order modes.
Solution Approach 2:
The patent uses composite material structures with different refractive indices arranged in specific layers. The core layer material has a higher refractive index than the cladding layer materials, creating a composite structure that provides strong confinement for the fundamental mode. This composite arrangement allows the waveguide to support high optical power in the fundamental mode while preventing higher-order modes from being supported, thus achieving both high power and single-mode operation.
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 enables high-power single-mode operation by ensuring the fundamental mode has a lower lasing threshold than higher order modes, thereby maintaining single-mode output with increased optical power.
Implementation Method 1
a first product of an overlap of the first optical mode with the grating and an overlap of the first optical mode with the active region is greater than a second product of an overlap of the at least one second optical mode with the grating and an overlap of the at least one second optical mode with the active region
Data Source
AI summary
A laser including a grating configured to reduce lasing threshold for a selected vertically confined mode as compared to other vertically confined modes.