Combined Gain-DBR VCSEL Structure for Wider Tuning Range
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Solution Overview
Problem
Current tunable Vertical-Cavity Surface-Emitting Lasers (VCSELs) face limitations in tuning range due to the length of the laser cavity and the bandwidth of the laser cavity mirrors, which restricts their application in optical coherence tomography (OCT) where wide tuning range is crucial for depth resolution.
Innovation Solution
The solution involves shortening the overall cavity length by integrating the gain section within the Distributed Bragg Reflector (DBR), specifically placing quantum wells between high and low index layers of the DBR, allowing for a more compact design suitable for semiconductor material systems like AlGaAs/GaAs, enabling wider tuning ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the laser cavity length is increased to improve tuning range, then the tuning range is improved, but the free-spectral range decreases causing another lasing mode to pop up one FSR away
Solution Approach 1:
The gain section is nested within the DBR mirror structure, with quantum wells positioned between the high and low index layers of the DBR. This integration allows the gain medium to be embedded within the reflector itself, creating a compact design that shortens the overall cavity length while maintaining the necessary optical functions for wide tuning range and stable single-mode operation
2Adaptability or versatility
If conventional separate gain section and DBR mirror design is used, then the structure is simpler, but the overall cavity length is longer reducing tuning range
Solution Approach 1:
The patent merges the gain section and DBR mirror into a single integrated structure. The quantum wells are placed within the DBR layers, combining the functions of light amplification and wavelength-selective reflection in one compact component, thereby shortening the cavity length and enabling wider tuning range
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 approach enhances the tuning range of VCSELs by approximately 20% compared to conventional designs, allowing for broader spectral coverage and increased power output without penalizing tunability, making them more suitable for high-power applications like OCT.
Implementation Method 1
a distributed Bragg reflector and quantum wells located in the distributed Bragg reflector
Implementation Method 2
quantum wells located in the distributed Bragg reflector
Data Source
AI summary
A vertical cavity surface emitting laser (VCSEL) has a shortened overall laser cavity by combining the gain section with a distributed Bragg reflector (DBR). The overall cavity length can be contracted by placing gain structures inside the DBR. This generally applies to a number of semiconductor material systems and wavelength bands, but this scheme is very well suited to the AlGaAs/GaAs material system with strained InGaAs quantum wells as a gain medium, for example.