Semiconductor Laser Feedback Grating for Current Confinement
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Solution Overview
Problem
Existing semiconductor lasers face challenges in achieving spatial limitation of the active region to prevent current expansion and effective mode selection of laser radiation, leading to inefficient laser generation and low yield of spectrally single-mode lasers.
Innovation Solution
A semiconductor laser with a multilayer structure featuring a web and material removal areas adjacent to it, where an insulation layer and lattice structure layer are arranged such that the lattice structure layer is positioned below the active region, typically within 100 nm, to enable optical coupling and prevent current expansion, allowing for effective mode selection and high yield of single-mode lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If material is removed perpendicular to the substrate surface to spatially limit the active region, then current spreading is prevented, but the active region is completely removed along the material removal direction making mode selection difficult
Solution Approach 1:
The patent transitions from vertical material removal to lateral material removal, changing the dimension of structuring. By removing material laterally adjacent to the ridge rather than vertically, the active region is spatially limited in the plane of layer propagation while maintaining sufficient thickness for optical feedback. This dimensional change resolves the contradiction by preserving mode selection capability while achieving current confinement.
2Manufacturing precision
If vertical grating structures are used for mode selection, then optical feedback is achieved, but manufacturing complexity increases and yield of spectrally single-mode lasers decreases
Solution Approach 1:
The patent extracts the grating structure from the vertical dimension and places it laterally adjacent to the active region. By taking out the grating structure from overlapping with the active region and positioning it in the laterally removed material area, the design simplifies manufacturing while maintaining optical feedback functionality. This extraction reduces manufacturing complexity and improves yield.
Solution Approach 2:
The patent introduces an insulating layer as an intermediary between the laterally positioned grating structure and the active region. This intermediary layer enables optical feedback while electrically isolating the grating structure from the active region, simplifying the manufacturing process and reducing complexity compared to vertical integrated structures.
3Reliability
If the grating structure layer is positioned far below the active region, then current spreading is prevented, but optical coupling for mode selection becomes ineffective
Solution Approach 1:
The patent applies local quality by positioning the grating structure layer laterally adjacent to the active region rather than uniformly below it. This lateral positioning creates local optical coupling where needed while maintaining current confinement. The grating structure is placed in the material removal region immediately adjacent to the ridge, providing localized optical feedback without requiring vertical proximity.
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 effectively limits current expansion and achieves precise mode selection, resulting in a higher percentage yield of spectrally monomode semiconductor lasers with improved manufacturing efficiency and cost-effectiveness.
Implementation Method 1
it is also known to arrange optical feedback elements above and/or below the active region, which enable mode selection of the laser radiation
Implementation Method 2
arrange an optical feedback element as close as possible to the active region, thus enabling optical feedback and the resulting mode selection of the laser radiation in the active region
Implementation Method 3
the necessity for spatial limitation is generally caused by the problem of current spreading, which refers to the spreading of a pump current within the active region
Data Source
Figure 1A~1C
Figure 2~3
Figure 4~5
AI summary
The invention relates to a semiconductor laser (01) comprising a multilayer structure (04) comprising a bridge (20) and material removal areas (16, 18) adjacent laterally to the bridge (20), wherein the multilayer structure (04) is arranged on a substrate (02) and wherein a layer propagation plane (26) is defined by a surface of the substrate (02), the bridge (20) has at least one active region (10) and at least the active region (10) is spatially limited in one dimension of the layer propagation plane (26) by a transition (22, 24) between the bridge (20) and the material removal areas (16, 18), wherein the active region (10) has a layer structure to form an interband cascade laser, wherein at least in the material removal areas (16, 18) an insulating layer (28) and a lattice structure layer (30) arranged above it are provided.wherein the insulating layer (28) and the lattice structure layer (30) are arranged in the material removal areas (16, 18) such that the lattice structure layer (30) is located below, but not more than 100 nm below, a lower edge of the active region (10), wherein the lattice structure layer (30) comprises a metal.