Broad-Stripe Diode Laser GRIN Structure for Mode Confinement
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Solution Overview
Problem
Wide-strip semiconductor lasers with an EDAS design face issues of reduced optical mode confinement and increased threshold current due to the fundamental mode shifting away from the active region, leading to reduced conversion efficiency and temperature sensitivity.
Innovation Solution
A diode laser with an ETAS design incorporating gradient-index (GRIN) layers in the transition regions between waveguide and active layers, achieving triple asymmetry to localize the fundamental mode within the active layer without widening the p-type waveguide, thereby enhancing optical mode confinement and maintaining high conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an EDAS design with a narrow p-type waveguide is used, then series resistance and optical losses are reduced, but the fundamental mode maximum shifts away from the active region, reducing optical mode confinement and increasing threshold current
Solution Approach 1:
The patent applies asymmetry by introducing gradient-index (GRIN) layers with different thicknesses on the n-type and p-type sides of the active layer. The n-type GRIN layer has a greater thickness than the p-type GRIN layer, creating an asymmetric structure that shifts the fundamental mode maximum back into the active region while preserving the narrow p-type waveguide geometry. This asymmetric design enables simultaneous achievement of low optical losses and high optical mode confinement.
Solution Approach 2:
The patent changes the refractive index parameter by introducing gradient-index (GRIN) layers with continuously varying refractive indices. These GRIN layers create smooth transitions between regions of different refractive indices, allowing control over the fundamental mode distribution. By adjusting the thickness and gradient parameters of the GRIN layers, the mode confinement is optimized without increasing the p-type waveguide width.
2Reliability
If the quantum film is shifted towards the n-region to increase mode confinement, then optical mode confinement is improved, but the advantages of EDAS design are not achieved
Solution Approach 1:
The patent segments the waveguide structure by introducing separate gradient-index (GRIN) layers on both the n-type and p-type sides of the active layer. This segmentation allows independent optimization of each side: the p-type side maintains a narrow waveguide for low series resistance, while the n-type side has a thicker GRIN layer for enhanced mode confinement. The segmented structure enables simultaneous achievement of both goals without compromising either.
3Reliability
If a multi-quantum-film configuration is used to increase mode confinement, then optical mode confinement is improved, but transparency current density and threshold current increase drastically, reducing conversion efficiency
Solution Approach 1:
The patent changes the structural parameters by introducing gradient-index (GRIN) layers with continuously varying refractive indices instead of using multiple quantum films. This parameter change allows achievement of high optical mode confinement through refractive index gradient control rather than through multiple active regions. The single-quantum-film configuration with GRIN layers maintains low transparency current density and high conversion efficiency while providing sufficient mode confinement.
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 ETAS design significantly increases mode confinement, allowing for higher conversion efficiencies and reduced temperature sensitivity, while also extending the use of laser diodes to high-temperature ranges and improving far-field angles without significant power losses.
Implementation Method 1
the first intermediate layer and, optionally, the second intermediate layer are gradient-index layers (GRIN layers) with a continuous refractive index profile
Implementation Method 2
the refractive index profile exhibits a kink at these locations
Data Source
Figure 1~2A
Figure 2B
Figure 3A
AI summary
The present invention relates to a laser diode having an improved mode profile. In particular, the present invention relates to a broad stripe semiconductor laser based on an extreme double asymmetric structure (EDAS), wherein, by means of an optimized mode profile having an improved mode confinement, the leakage current rates and the series resistance can be lowered and the charge carrier density within the light-guiding waveguide and the active zone can be reduced. The diode laser according to the invention comprises a first cladding layer (14) of n-conducting configuration, a first waveguide layer (12) of n-conducting configuration, which is arranged on the first cladding layer (14), an active layer (10), which is suitable for generating radiation and which is arranged on the first waveguide layer (12), a second waveguide layer (16) of p-conducting configuration, which is arranged on the active layer (10), a second cladding layer (18) of p-conducting configuration, which is arranged on the second waveguide layer (16), wherein a first intermediate layer (11) of n-conducting configuration is configured as a transition region between the first waveguide layer (12) and the active layer (10), and a second intermediate layer (15) of p-conducting configuration is configured as a transition region between the second waveguide layer (16) and the active layer (10). In this case, the diode laser according to the invention is characterized in that the asymmetry ratio of the thickness of the first intermediate layer (11) to the sum of the thickness of the first intermediate layer (11) and the thickness of the second intermediate layer (15) is less than or greater than 0.5.