Broad Area Semiconductor Laser Mode Suppression via Refractive Index Geometry
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Solution Overview
Problem
Conventional broad area semiconductor laser devices face challenges in reducing beam divergence angles without increasing the length of the filter region, which leads to higher threshold currents and decreased slope efficiency due to increased loss and higher order mode oscillation.
Innovation Solution
The design incorporates a refractive index waveguide type broad area semiconductor laser device with a waveguide region and a filter region, where the active region protrudes or recesses with respect to the filter region, allowing for the suppression of higher order modes by adjusting the refractive indices and geometries to control light divergence, thereby reducing the need for longer filter regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the length of the filter region is increased to suppress higher order modes and reduce beam divergence, then the beam divergence angle is reduced, but the threshold current increases and slope efficiency decreases due to increased loss
Solution Approach 1:
The patent applies local quality by creating a protruding portion at a specific location (the interface between waveguide region and filter region) that modifies the local refractive index distribution. This localized structural modification enables mode filtering without requiring a long filter region, thus avoiding the energy loss that would occur with extended filter regions.
Solution Approach 2:
The invention transitions from controlling mode filtering solely through the length of the filter region (one-dimensional approach) to utilizing the vertical protrusion dimension. By creating a protruding portion that extends in the vertical direction at the interface, the patent adds a new dimensional parameter for controlling light propagation and mode selection, thereby achieving effective filtering without increasing the horizontal length of the filter region.
2Stability of the object's composition
If the filter region length is increased to sufficiently diverge light and suppress higher order mode oscillation, then higher order modes are suppressed, but device properties deteriorate due to increased loss
Solution Approach 1:
The protruding portion creates a localized refractive index variation at the critical interface between waveguide and filter regions. This local modification is sufficient to disrupt higher order mode propagation and stabilize the oscillation characteristics, eliminating the need for long filter regions that would cause energy loss.
Solution Approach 2:
The protruding portion performs preliminary mode filtering at the interface between waveguide and filter regions, before light enters the main filter region. This preliminary action pre-diverges higher order modes, reducing the burden on the filter region length and enabling effective mode suppression with minimal filter region extension.
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 effectively suppresses higher order modes, reduces beam divergence, and maintains or improves the efficiency of the semiconductor laser device by minimizing loss and maintaining low threshold currents and high slope efficiency.
Implementation Method 1
an effective refractive index of the waveguide region is smaller than an effective refractive index of the filter region
Implementation Method 2
a resonator that has a front end surface and a rear end surface, and includes a waveguide region and a filter region
Data Source
AI summary
A broad area semiconductor laser device includes a waveguide region and a filter region. The waveguide region includes an active region into which current is injected, and a cladding region that sandwiches the active region. The active region either protrudes or is recessed with respect to the filter region, so as to promote the divergence of higher order modes in the filter region.