Single-mode VCSEL with Photonic Band-Gap Mode Confinement
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Solution Overview
Problem
Current VCSEL designs face challenges in achieving large-aperture single-mode high-power operation due to limitations in lateral mode confinement and the complexity of existing methods, which often result in high process variations and instability.
Innovation Solution
The VCSEL design incorporates a structure with a central light aperture region, a mode-shaping region, and a mode-confinement region, where the mode-shaping region has a shorter photon lifetime than the light aperture region, and the mode-confinement region provides lateral confinement using a photonic band-gap effect, allowing for efficient lateral mode control and single fundamental mode operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lateral mode confinement methods are used, then mode confinement is achieved, but process variations and instability increase
Solution Approach 1:
The patent changes the physical parameter of photon lifetime in different regions (shorter in mode-shaping region, longer in light aperture region) to achieve mode control. This parameter change enables reliable single-mode operation without relying on complex manufacturing processes, thereby reducing process variations while maintaining device stability.
Solution Approach 2:
The patent segments the VCSEL structure into distinct functional regions: light aperture region, mode-shaping region, and mode-confinement region. Each region has specific properties (photon lifetime characteristics) that work together to achieve mode control. This segmentation allows independent optimization of each region, reducing the coupling of process variations and improving overall device reliability.
2Reliability
If complex mode confinement structures are used, then lateral mode control is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by giving different photon lifetime characteristics to different regions of the VCSEL. The mode-shaping region has shorter photon lifetime while the light aperture region has longer photon lifetime. This local differentiation achieves effective mode control without requiring complex overall structures, maintaining device simplicity while improving mode selectivity.
Solution Approach 2:
Instead of using complex physical structures to confine modes, the patent inverts the approach by using regions with shorter photon lifetime (mode-shaping region) to control modes, rather than relying on traditional long-photon-lifetime confinement structures. This inversion simplifies the device structure while achieving reliable mode control.
3Power
If larger aperture is used, then output power increases, but higher-order modes are harder to suppress
Solution Approach 1:
The patent applies preliminary action by introducing a mode-shaping region with shorter photon lifetime before the light reaches the light aperture region. This preliminary mode-shaping action suppresses higher-order modes early in the optical path, allowing the subsequent light aperture region to support larger apertures for high power output while maintaining single-mode operation. The mode-shaping region prepares the optical field in advance to prevent higher-order mode development.
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 design enables large-aperture single-mode high-power operation with reduced lateral radiation losses and improved mode selectivity, promoting single fundamental mode operation while suppressing higher-order modes, and decouples lateral mode confinement from current confinement, enhancing device reliability and reproducibility.
Implementation Method 1
the mode-confinement region provides lateral confinement using a photonic band-gap effect
Implementation Method 2
The mode confinement in conventional optical waveguides is achieved by having a core with a high refractive index surrounded by a cladding with a lower refractive index. This results in a waveguide based on the principle of total internal reflection.
Data Source
AI summary
This specification discloses a VCSEL (Vertical-Cavity Surface-Emitting Laser) device with single-mode output and optionally single polarization output. This device is given by lateral mode confinement by the PBG (Photonic Band-Gap) effect by shallow etching in a partial VCSEL top mirror. The PBG area encircles a MS-region (Mode-Shaping region), which is characterized by large longitudinal mode losses. The MS-region encircles the LA-region (Light Aperture region), which is characterised by low longitudinal mode losses. The MS-region does not contribute to the lateral mode-confinement to the LA-aperture, and the lateral modes confined by the PBG area. The VCSEL is thus optimized for single fundamental mode operation.