VCSEL Cavity Design With Integrated DBR Gain for Wider Tuning
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Solution Overview
Problem
Current swept source Optical Coherence Tomography (OCT) applications are limited by the narrow tuning range of Vertical-Cavity Surface-Emitting Lasers (VCSELs), which restricts depth resolution, particularly in the 1310 nm and 1060 nm bands, due to the limitations in laser cavity bandwidth and length.
Innovation Solution
The overall cavity length of VCSELs is shortened by integrating the gain section within a Distributed Bragg Reflector (DBR), allowing for a wider tuning range by placing quantum wells inside the DBR, particularly suited for the AlGaAs/GaAs material system with strained InGaAs quantum wells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the VCSEL cavity length is reduced to broaden the tuning range, then the tuning range increases, but the Free Spectral Range (FSR) increases causing other lasing modes to appear
Solution Approach 1:
The patent combines the gain section with the DBR mirror structure by integrating quantum wells directly within the DBR layers. This merging eliminates the need for a separate gain section, effectively reducing the overall cavity length while maintaining single-mode operation through the DBR's reflective selectivity.
Solution Approach 2:
The patent changes the cavity length parameter by reducing it through the integrated structure, which broadens the tuning range. The DBR's wavelength-selective reflection compensates for the reduced cavity length, preventing other modes from appearing despite the shorter cavity.
2Power
If more quantum wells are added to increase output power, then the power increases, but the device complexity increases
Solution Approach 1:
The gain section and DBR mirror are merged into a single integrated structure where quantum wells are embedded within the DBR layers. This allows multiple quantum wells to be added for increased power output without requiring separate gain section and mirror structures, thereby limiting the increase in device complexity.
3Adaptability or versatility
If the gain section is separated from the DBR mirror, then the design flexibility is improved, but the overall cavity length increases reducing the tuning range
Solution Approach 1:
The patent merges the gain section and DBR mirror into a single integrated structure, achieving the opposite of separation. This integration reduces the overall cavity length to broaden the tuning range while the DBR's wavelength-selective properties maintain single-mode operation.
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 enhances the tuning range of VCSELs from approximately 90 nm to 110 nm, improving the depth resolution in OCT applications without penalizing tunability, and allows for high-power operation by adding more quantum wells without affecting the tuning range.
Implementation Method 1
a distributed Bragg reflector and quantum wells located in the distributed Bragg reflector
Implementation Method 2
quantum wells located in shallow layers of the distributed Bragg reflector
Data Source
Figure 1A~1B
Figure 2A~2D
Figure 2B~2E
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.