Semiconductor Laser Undoped Clad Reduces Internal Loss
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Solution Overview
Problem
Conventional high power semiconductor laser devices face challenges in reducing internal optical loss, which limits the length of the resonator and affects optical output efficiency, leading to beam shape distortion and mismatch with optical systems.
Innovation Solution
Incorporating intentionally undoped optical loss confinement regions in the conductivity type clad layers adjacent to the optical guide layers, reducing internal loss and allowing for a longer resonator design without increasing the width, thereby enhancing optical output efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the resonator length is increased to enhance output, then the laser output power is improved, but the internal optical loss increases causing efficiency degradation
Solution Approach 1:
The patent applies local quality by creating an undoped region specifically in the clad layer adjacent to the active layer, while other regions maintain their original doping levels. This localized modification reduces optical loss in the critical region where light propagates, allowing longer resonator lengths without proportionally increasing internal loss. The undoped region has different optical properties (lower absorption) compared to doped regions, directly addressing the contradiction between length and loss.
Solution Approach 2:
The patent changes the doping parameter (from doped to undoped) in the clad layer to alter its optical absorption characteristics. By removing dopants from the clad layer adjacent to the active layer, the optical absorption coefficient is reduced, thereby decreasing internal optical loss. This parameter change enables the resonator to be extended in length while maintaining acceptable loss levels, resolving the contradiction between power output and energy loss.
2Loss of energy
If the optical guide layers are thickened to reduce internal optical loss, then the optical cavity volume increases lowering loss, but higher order mode beams are triggered distorting beam shape
Solution Approach 1:
Instead of uniformly thickening optical guide layers throughout the structure, the patent applies local quality by creating an undoped region only in the clad layer adjacent to the active layer. This localized approach reduces optical loss in the critical light propagation region without increasing the overall optical guide layer thickness, thereby avoiding excitation of higher order modes and maintaining beam shape quality.
Solution Approach 2:
The patent shifts the solution from the vertical dimension (thickening optical guide layers) to the compositional dimension (changing doping status of the clad layer). By modifying the doping concentration in the clad layer rather than increasing guide layer thickness, the patent achieves reduced optical loss without altering the geometric dimensions that would trigger higher order modes, thus preserving beam shape.
3Temperature
If the resonator length is increased to enhance output, then the current density decreases restraining temperature rise, but the internal optical loss degrades efficiency
Solution Approach 1:
The patent changes the doping parameter of the clad layer to create an undoped region, which alters the optical absorption characteristics. This parameter change reduces internal optical loss per unit length, allowing the resonator to be extended in length. The extended length simultaneously achieves the secondary benefit of reduced current density and temperature rise, effectively resolving the contradiction between temperature control and efficiency maintenance.
Solution Approach 2:
The patent segments the clad layer into doped and undoped regions, with the undoped region positioned adjacent to the active layer. This segmentation creates a low-loss optical pathway for light propagation while maintaining appropriate electrical confinement in other regions. The segmented structure enables longer resonator lengths with controlled internal loss, achieving both temperature management and efficiency preservation.
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
The solution significantly reduces internal loss, enabling a longer resonator design that improves current density and light emitting efficiency while minimizing beam distortion, resulting in a 10-14% increase in optical output with a moderate increase in driving voltage.
Implementation Method 1
an intentionally undoped optical loss confinement region which is formed in a portion of at least one of the first and second conductivity type clad layers overlapping laser beam distribution
Data Source
AI summary
In a high power semiconductor laser device, first and second conductivity type clad layers are provided. An active layer is interposed between the first and second conductivity type clad layers. A first optical guide layer is disposed between the first conductivity type clad layer and the active layer. A second optical guide layer is disposed between the second conductivity clad layer and the active layer. Also, an intentionally undoes optical loss confinement region is formed in a portion of at least one of the first and second conductivity type clad layers overlapping laser beam distribution.