Back-Side Emitting VCSEL with Nanostructure Reflector
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Solution Overview
Problem
Vertical cavity surface emitting lasers (VCSELs) face challenges in light control and emission characteristics due to the limitations of distributed Bragg reflectors (DBR), which have high reflectivity but low heat conductivity and asymmetrical optical output, making them less efficient for power consumption and integration in 3D shape recognition applications.
Innovation Solution
A back side emitting light source array device is developed, featuring a substrate with a DBR, spaced gain layers, and a nanostructure reflector with sub-wavelength dimensions, where the reflectivity of the DBR is less than that of the nanostructure reflector, allowing light to be emitted through the substrate. This device includes a meta-surface layer with sub-wavelength dimensions and a heat sink for improved heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a distributed Bragg reflector (DBR) is used to constitute a laser resonator in VCSEL, then high reflectivity (about 90% or higher) is achieved, but heat conductivity becomes low due to phonon scattering at material boundaries
Solution Approach 1:
The DBR structure is divided into multiple alternating layers of materials with different refractive indices. Each layer is thin (lambda/4 thickness) and works together to achieve high reflectivity through constructive interference, while the segmented structure manages heat distribution across multiple interfaces rather than a single boundary.
Solution Approach 2:
The DBR uses composite material structures with alternating high and low refractive index materials (such as AlGaAs and GaAs layers). This composite approach enables high reflectivity through refractive index contrast while the specific material selection and layer design influence thermal conduction pathways.
2Use of energy by moving object
If VCSEL is used instead of edge emitting laser (EEL), then power consumption is reduced and integration is improved, but optical gain length becomes shorter limiting performance
Solution Approach 1:
The laser emission transitions from edge-emitting (lateral direction) to vertical cavity surface-emitting (vertical direction perpendicular to the substrate). This dimensional change allows the optical cavity to form vertically between DBR mirrors, enabling compact lateral footprint while maintaining sufficient vertical gain length for lasing action.
Solution Approach 2:
The invention optimizes the vertical cavity length and gain layer thickness parameters to achieve sufficient optical gain within the shortened vertical dimension. By adjusting the thickness of active regions and the number of DBR periods, the system compensates for the reduced gain length while maintaining low power consumption and high integration density.
3Reliability
If VCSEL provides circular symmetrical output mode, then efficient connection to optical fiber and stable high-speed modulation is achieved, but asymmetrical optical output of EEL is lost
Solution Approach 1:
The circular symmetrical output mode of VCSEL serves multiple functions: it enables efficient coupling to circular optical fibers, provides isotropic radiation pattern for omnidirectional applications, and supports stable high-speed modulation. This universal output characteristic makes VCSEL adaptable to various optical systems unlike directionally constrained EEL.
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 enhances light emission efficiency, reduces power consumption, and improves integration by enabling stable high-speed modulation with low noise, addressing the limitations of DBR in VCSELs for accurate 3D shape recognition.
Implementation Method 1
The VCSEL includes a distributed Bragg reflector (DBR) exhibiting a high reflectivity of about 90% or higher to constitute a laser resonator. A DBR may include a stacked structure of tens of pairs of two materials with different refractive indices to obtain a high reflectivity.
Implementation Method 2
a nanostructure reflector provided on the plurality of gain layers opposite to the DBR, and including a plurality of nanostructures having a sub-wavelength shape dimension, wherein a reflectivity of the DBR is less than a reflectivity of the nanostructure reflector such that the light generated is emitted through the substrate.
Implementation Method 3
a plurality of gain layers which are provided on the DBR, the plurality of gain layers being spaced apart from one another, and each of the plurality of gain layers being configured to individually generate light
Implementation Method 4
a heat sink provided on the nanostructure reflector opposite to the plurality of gain layers.
Data Source
AI summary
Provided is a back side emitting light source array device and an electronic apparatus, the back side emitting light source array device includes a substrate, a distributed Bragg reflector (DBR) provided on a first surface of the substrate, a plurality of gain layers which are provided on the DBR, the plurality of gain layers being spaced apart from one another, and each of the plurality of gain layers being configured to individually generate light, and a nanostructure reflector provided on the plurality of gain layers opposite to the DBR, and including a plurality of nanostructures having a sub-wavelength shape dimension, wherein a reflectivity of the DBR is less than a reflectivity of the nanostructure reflector such that the light generated is emitted through the substrate.