Laser Diode Current Confinement for Stable NFP
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Solution Overview
Problem
Broad-area laser diodes face challenges in maintaining a stable and uniform near-field pattern (NFP) due to high-order mode generation and filament emission, which can lead to degraded display quality and nonuniform brightness, especially under temperature or current fluctuations.
Innovation Solution
The implementation of strip-shaped current confinement structures with convex or concave portions in a stacked structure on a semiconductor substrate, guiding light through a waveguide structure formed by the refractive index distribution, stabilizes the transverse mode and suppresses filament emission, thereby achieving a stable and uniform NFP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a broad-area laser diode with a widened waveguide is used, then high output capability is achieved, but high-order mode generation and filament emission occur causing unstable and nonuniform NFP
Solution Approach 1:
The patent introduces current confinement structures with varying widths along the extending direction, creating local variations in current density distribution. This local quality change allows different sections of the active layer to have optimized current confinement, suppressing high-order modes and filament emission while maintaining overall high output capability through the broad-area design.
Solution Approach 2:
The patent modifies the geometric parameters of the current confinement structures by varying the width along the extending direction. This parameter change transforms the uniform wide-waveguide structure into a non-uniform structure with controlled current distribution, thereby stabilizing the NFP while preserving the high power output characteristic of broad-area lasers.
2Power
If the stripe width is increased to at least 5 μm or above, then high output capability is achieved, but control of NFP becomes difficult and stable uniform NFP is hardly obtained
Solution Approach 1:
By introducing current confinement structures with locally varied widths within the broad-area device, the patent achieves precise control over current distribution in different regions. This local quality optimization enables accurate NFP shape control despite the overall large stripe width, resolving the contradiction between high power output and manufacturing precision.
3Power
If a broad-area laser diode is used for display applications, then high output capability is achieved, but display quality is degraded due to flicker and nonuniformity of brightness
Solution Approach 1:
The patent modifies the current confinement structure geometry parameters to achieve stable and uniform NFP. This parameter optimization eliminates flicker and brightness nonuniformity issues, ensuring reliable display quality while maintaining the high output capability required for display applications.
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 ensures a stable and uniform NFP, reducing the risk of flicker and brightness nonuniformity, even under changes in temperature or injection current, thereby enhancing display quality.
Implementation Method 1
light emitted in the active layer is guided by a waveguide structure corresponding to a refractive index distribution formed by the current confinement structure and the concave portion
Implementation Method 2
light emitted in the active layer is guided by a waveguide structure corresponding to a refractive index distribution formed by the current confinement structure and the convex portion
Data Source
AI summary
Provided is a laser diode which realizes NFP with a stable and uniform shape. The laser diode includes, on a semiconductor substrate, an active layer, one or a plurality of strip-shaped current confinement structures confining a current which is injected into the active layer, and a stacked structure including one or a plurality of strip-shaped convex portions extending in an extending direction of the current confinement structure.