Surface-Emitting Laser Mirror Design for Stable Self-Mixing
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Solution Overview
Problem
Conventional surface-emitting lasers (SELs) for self-mixing interferometry (SMI) face limitations in beam quality, mode stability, and reliability due to fundamental transverse mode operation, which restricts feedback coupling and increases noise, especially at higher current densities and smaller oxide apertures.
Innovation Solution
The development of SEL optoelectronic devices with a non-mode-limiting oxide aperture and a high-contrast grating dominated top mirror, combined with a monolithically integrated photodetector, enables single-mode operation at higher power levels and lower noise, enhancing beam quality and reliability by maximizing feedback and coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If fundamental transverse mode operation is used in conventional SELs, then beam quality is maintained, but feedback coupling is restricted and noise increases
Solution Approach 1:
The patent changes the transverse mode parameter from fundamental mode to higher-order mode operation. This allows the laser to achieve larger mode sizes and improved feedback coupling efficiency while maintaining acceptable beam quality through careful mode selection and cavity design. The higher-order modes provide larger spatial extent for better target coupling without sacrificing the coherence required for SMI.
2Stability of the object's composition
If oxide aperture is reduced to maintain single-mode operation, then beam quality is preserved, but current density increases and reliability decreases
Solution Approach 1:
The patent changes the operating mode parameter to higher-order modes, which naturally provide larger mode sizes without requiring small oxide apertures. This parameter change allows the use of larger oxide apertures (e.g., 5-10 microns instead of sub-3.5 microns), thereby reducing current density and improving device reliability while maintaining single-transverse-mode operation for SMI applications.
3Power
If higher power levels are used to improve signal strength, then SMI sensitivity increases, but multi-mode operation introduces noise
Solution Approach 1:
The patent selects specific higher-order transverse modes that can support higher power levels while maintaining single-mode operation. By carefully choosing the mode structure and cavity parameters, the system achieves higher output power for improved SMI signal strength without the noise contamination that would result from multi-mode operation. The selected modes provide adequate spatial extent for power scaling while preserving the coherence and single-mode characteristics required for low-noise SMI.
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 allows for improved SMI performance with increased wavelength modulation, reduced noise, and enhanced reliability, enabling more precise and stable self-mixing interferometry applications.
Implementation Method 1
coherent or partially coherent light emitted by the SEL is reflected and/or scattered from a target and re-coupled into an optical cavity of the SEL
Implementation Method 2
a high-contrast grating dominated top mirror... The MHCG dominated top mirror may include near-subwavelength (e.g., λ/2 to λ) periodic or aperiodic structures
Implementation Method 3
This re-coupling can also create a measurable change in the photodiode current, for example, when the SEL is integrated with a photodiode
Implementation Method 4
An SEL (e.g, a VCSEL or PCSEL) with a photodetector can be used for SMI applications in which coherent or partially coherent light emitted by the SEL
Implementation Method 5
SMI is a coherent sensing technology... coherent or partially coherent light emitted by the SEL is reflected and/or scattered from a target and re-coupled into an optical cavity of the SEL
Data Source
AI summary
An optoelectronic device may include a first set of distributed Bragg reflective (DBR) layers, a second set of DBR layers, a gain region, and an enclosure layer between the gain region and the second set of DBR layers. In some cases, the enclosure layer defines a non-limiting mode oxide aperture. The optoelectronic device may also include a high contrast grating (HCG) mirror element disposed on a side of the second set of DBR layers. In some cases, the HCG mirror element has a first reflection coefficient that is greater than a second reflection coefficient of the second set of DBR layers. Another optoelectronic device may include a photonic crystal (PhC) mirror layer and a gain region disposed between the PhC mirror layer and a set of DBR layers.