Monolithic Edge-Emitting Laser Diodes with Tunnel Junctions
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Solution Overview
Problem
Existing LIDAR systems using near-infrared lasers are not eye-safe and have limited efficiency for long-wavelength applications, while stacked-solder-bonded laser diodes face challenges in focusing separated outputs for long-range applications.
Innovation Solution
Development of edge-emitting semiconductor lasers with multiple monolithic diodes connected by tunnel junctions, using the AlInGaAs/InGaAsP/InP material system, emitting in long wavelengths (1250 nm to 1720 nm), with optimized quantum well structures and doping concentrations to achieve high efficiency and eye-safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If stacked-solder-bonded laser diodes are used to increase output power, then the output power is doubled or tripled, but the laser outputs are separated and difficult to focus accurately for long-range applications
Solution Approach 1:
The patent merges multiple laser diodes into a single monolithic structure where multiple active regions are integrated within one continuous waveguide. This combining approach allows multiple laser outputs to be generated from a single unified optical path, eliminating the separation issue inherent in stacked-solder-bonded configurations while maintaining high output power through multiple active regions.
2Object-affected harmful factors
If long wavelength lasers (>1300 nm) are used for eye-safe operation, then eye safety is achieved, but the efficiency drops to about half of 905 nm lasers
Solution Approach 1:
The patent employs parameter changes by optimizing the quantum well structures, material compositions, and doping concentrations in the AlInGaAs/InGaAsP/InP system to achieve high efficiency at long wavelengths. By adjusting these parameters, the invention overcomes the typical efficiency drop at wavelengths >1300 nm while maintaining eye-safe operation.
Solution Approach 2:
The patent uses composite material structures with multiple layers including AlInGaAs barriers, InGaAsP quantum wells, and InP cladding layers. This composite approach allows optimization of each layer's properties to achieve both high efficiency and long wavelength emission, overcoming the limitations of single-material systems.
3Use of energy by moving object
If multiple monolithic laser diodes are connected by tunnel junctions, then high efficiency approaching 1 W/A is achieved, but the device complexity increases
Solution Approach 1:
The patent segments the laser structure into multiple active regions separated by tunnel junctions within a single monolithic device. This segmentation allows each active region to be independently optimized for high efficiency operation while the tunnel junctions provide electrical isolation, enabling high overall efficiency despite the increased structural complexity.
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 achieves higher efficiency approaching 1 W/A, maintains eye safety, and enables accurate focusing for long-range LIDAR applications, suitable for military, automotive, and industrial uses by ensuring consistent emission wavelengths across multiple diodes.
Implementation Method 1
the monolithic laser diodes are connected one to another by one or more tunnel junctions
Implementation Method 2
each monolithic laser diode comprises an active region with barriers and no more than three quantum wells constructed from various ratios of aluminum, gallium, indium and arsenic
Data Source
AI summary
A monolithic edge emitting semiconductor laser comprising multiple laser diodes using aluminum indium gallium arsenide phosphide AlInGaAs/InGaAsP/InP material system, emitting in long wavelengths (1250 nm to 1720 nm). Each laser diode contains an active region comprising aluminium indium gallium arsenide quantum wells (AlInGaAs QW) and aluminum indium gallium arsenide (AlInGaAs) barriers and is connected to the subsequent monolithic laser diode by highly doped, low bandgap and low resistive indium gallium arsenide junction called tunnel junction.