VCSEL DBR Phase Shift Layer for Lower Beam Divergence
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Solution Overview
Problem
Conventional VCSELs face challenges with optical intensity distribution causing large divergence angles, complicating design considerations and reducing light emission efficiency, especially in applications like 3D sensors and lidar, where optimizing divergence angle is crucial for detection distance, resolution, and signal-to-noise ratio.
Innovation Solution
The VCSEL device incorporates optical phase shift layers between DBR pairs, adjusting the peak optical intensity to shift outside the resonator cavity, using materials with specific refractive index ranges and thicknesses to reduce beam divergence without compromising efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the resonator cavity is expanded to suppress the divergence angle, then the beam divergence is reduced, but the light emission efficiency is lost and the epitaxial growth becomes slower and costlier
Solution Approach 1:
The patent modifies the optical path length within the resonator cavity by introducing an optical phase shift layer, changing the phase relationship of light waves without physically expanding the cavity. This parameter change allows the cavity to maintain its compact size while achieving the desired beam divergence control through phase manipulation of the optical field.
Solution Approach 2:
The optical phase shift layer acts as an intermediary element between the existing cavity structure and the desired beam output characteristics. This intermediate layer modifies the optical phase without requiring structural changes to the cavity itself, thereby maintaining light emission efficiency while achieving beam divergence suppression.
2Shape
If the resonator cavity is expanded to suppress the divergence angle, then the beam divergence is reduced, but the manufacturing cost increases due to slower epitaxial growth
Solution Approach 1:
Instead of changing the physical dimensions of the resonator cavity, the patent changes the optical parameters by introducing a phase shift layer with specific optical properties. This approach maintains the original cavity size and thus avoids the increased manufacturing costs associated with larger cavity structures.
3Illumination intensity
If the peak optical intensity is in the resonator cavity overlapping with the light emitting layer, then the optical intensity distribution is concentrated, but the service life and reliability are reduced due to aging
Solution Approach 1:
The patent extracts the peak optical intensity from the light emitting layer region by introducing the optical phase shift layer. This shifts the maximum intensity location to a different position in the optical path, reducing the degradation stress on the light emitting layer and thereby improving device reliability and service life.
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 effectively reduces beam divergence and enhances optical intensity distribution, improving detection capabilities and reliability of VCSELs in applications like lidar systems.
Implementation Method 1
One of the upper DBR structure and the lower DBR structure has at least one optical phase shift layer inserted between two adjacent ones of the DBR pairs. The at least one optical phase shift layer has a thickness of (2Nλ/4)+(1/4×Kλ), where N is a positive integer, K ranges from 0.8 to 1.2, and λ is a wavelength of a light emitted by the VCSEL device.
Implementation Method 2
The at least one optical phase shift layer has a refractive index of η, and 0.8η1≤η≤1.2η1 or 0.8η2≤n≤1.2η2, where the first material layer has a refractive index of η1, the second material layer has a refractive index of η2.
Implementation Method 3
A VCSEL is composed of a resonator cavity and two distributed Bragg reflectors (DBR) respectively located above and below the resonator cavity. Each of the upper DBR structure and the lower DBR structure has a plurality DBR pairs that are each formed from a first material layer with a low refractive index and a second material layer with a higher refractive index.
Data Source
AI summary
A VCSEL device includes a resonator cavity, an upper DBR structure and a lower DBR structure respectively located on opposite sides of the resonator cavity. Each of the upper DBR structure and the lower DBR structure has a plurality of DBR pairs that are formed from a first material layer and a second material layer. One of the upper DBR structure and the lower DBR structure has an optical phase shift layer inserted between two DBR pairs. The optical phase shift layer has a thickness of (2Nλ/4)+(1/4×Kλ), where N is a positive integer, K ranges from 0.8 to 1.2, and λ is a wavelength of a light emitted by the VCSEL device. A method of making the VCSEL device is included.