Quantum Cascade Laser Distributed Bragg Reflection Region
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Solution Overview
Problem
Quantum cascade lasers face challenges in achieving high reflectivity in their distributed Bragg reflection regions, leading to difficulties in laser oscillation due to light propagation discontinuities at the boundary between the laser body region and the distributed Bragg reflection region, with existing structures failing to effectively reflect light components propagating in the substrate.
Innovation Solution
The quantum cascade laser incorporates a substrate with etched low refractive index portions and high refractive index portions, where the high refractive index portions include semiconductor walls extending into the substrate, allowing for the reflection of both optical and substrate components of light, and includes reinforcement portions to enhance mechanical strength and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional distributed Bragg reflection region structure is used, then the device complexity is low, but the reflectivity is insufficient (below 80%) leading to light propagation discontinuities
Solution Approach 1:
The patent extends the Bragg reflection structure from a two-dimensional surface pattern into the third dimension by etching semiconductor walls into the substrate. This vertical extension creates multiple reflection interfaces at different depths, significantly enhancing reflectivity while maintaining a relatively simple overall structure.
Solution Approach 2:
The distributed Bragg reflection region employs a nested structure where alternating high refractive index semiconductor layers and low refractive index air gaps are embedded within the substrate. This nested arrangement of refractive index variations creates multiple internal reflection surfaces that work together to achieve high reflectivity.
2Reliability
If semiconductor walls are extended into the substrate to increase reflectivity, then the optical performance improves, but the mechanical strength may be compromised
Solution Approach 1:
The patent applies local quality by creating semiconductor walls with specific geometric characteristics at the Bragg reflection region, while the rest of the substrate maintains its original continuous structure. The localized etching creates reflection surfaces without compromising the overall mechanical integrity of the substrate.
Solution Approach 2:
The distributed Bragg reflection region creates a composite structure combining semiconductor material walls with air gaps. This composite arrangement provides both the optical functionality for high reflectivity and structural support, as the semiconductor walls maintain the mechanical framework while the air gaps provide the necessary refractive index contrast.
3Reliability
If the substrate is etched to create low refractive index portions, then light reflection improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the etching parameters including depth, width, and spacing of the semiconductor walls to achieve the desired reflectivity. By carefully controlling these geometric parameters, the structure achieves high reflectivity while remaining compatible with standard semiconductor fabrication capabilities.
Solution Approach 2:
The etching process creates preliminary structures (semiconductor walls and air gaps) that are subsequently filled or covered during device assembly. This preliminary action allows for precise control of the optical structure while accommodating variations in etching precision through subsequent manufacturing steps.
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 configuration achieves a high reflectivity of 80% or more for the distributed Bragg reflection region, reducing the threshold current and improving lasing characteristics, while also increasing the mechanical strength and durability of the device.
Implementation Method 1
a distributed Bragg reflection region disposed on the principal surface of the substrate, the distributed Bragg reflection region including one or more low refractive index portions and one or more high refractive index portions, the high refractive index portion having a refractive index higher than that of the low refractive index portion
Implementation Method 2
allowing for the reflection of both optical and substrate components of light
Data Source
AI summary
A quantum cascade laser includes a substrate having a principal surface; a laser body region disposed on the principal surface, the laser body region including a semiconductor laminate structure having an end facet, the laser body region having a waveguide structure extending along a waveguide axis; and a distributed Bragg reflection region disposed on the principal surface, the distributed Bragg reflection region including low and high refractive index portions that are alternately arranged in a direction of the waveguide axis. The end facet of the semiconductor laminate structure is optically coupled to the distributed Bragg reflection region. Each of the high refractive index portions includes a semiconductor wall including upper and lower portions that are arranged in a direction intersecting with the principal surface of the substrate. The principal surface is disposed between the upper and lower portions. The lower portion includes a part of the substrate.