Photonic Crystal Surface Laser Mesa Layout for Mode Stability
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Solution Overview
Problem
Photonic-crystal surface-emitting lasers face challenges in maintaining high beam quality and stability at high current injection levels due to difficulties in accurately manufacturing air holes and lattice constants, leading to potential beam quality degradation from higher-order mode oscillation.
Innovation Solution
A photonic-crystal surface-emitting laser element is designed with a photonic crystal layer, a first semiconductor layer, an active layer, and a second semiconductor layer, featuring a mesa structure within the air hole formation region to suppress higher-order mode oscillation, thereby maintaining basic mode stability and high beam quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If photonic crystal with small air holes is used to achieve high beam quality, then beam quality is improved, but manufacturing precision deteriorates due to difficulty in accurately manufacturing air hole size and lattice constant
Solution Approach 1:
The patent changes the structural parameters of the photonic crystal by introducing a mesa portion that modifies the air hole configuration. The mesa portion creates a region where air holes are removed or modified, effectively changing the lattice constant and air hole distribution in a controlled manner. This parameter change allows suppression of higher-order modes while maintaining manufacturability, as the mesa structure can be fabricated using standard semiconductor processing techniques rather than requiring precise control of every individual air hole.
2Power
If high current injection is applied to increase output power, then power is improved, but beam quality deteriorates due to higher-order mode oscillation
Solution Approach 1:
The patent applies preliminary anti-action by introducing the mesa portion structure before high current injection occurs. The mesa portion pre-establishes a refractive index distribution and optical field confinement that actively counteracts the tendency toward higher-order mode oscillation. This preliminary structural modification creates a potential well that confines the optical mode in the fundamental state, preventing higher-order modes from developing even when high current is injected, thus maintaining beam quality at high power levels.
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 suppresses higher-order mode oscillation, ensuring high beam quality and stability even at high current injection levels by reducing the threshold gain difference between basic and higher-order modes, resulting in unimodal laser light with minimal spread angle.
Implementation Method 1
a photonic crystal layer, including air holes arranged with two-dimensional periodicity in a plane parallel to the photonic crystal layer
Implementation Method 2
a mesa portion with a mesa shape formed at a surface of the second semiconductor layer, wherein the mesa portion is located inside the formation region of the air holes
Data Source
AI summary
A photonic-crystal surface-emitting laser element includes: a first semiconductor layer formed by embedding a photonic crystal layer that includes air holes arranged with two-dimensional periodicity in a formation region in a plane parallel to the photonic crystal layer; an active layer formed on the first semiconductor layer; a second semiconductor layer formed on the active layer; and a mesa portion with a mesa shape formed at a surface of the second semiconductor layer, wherein the mesa portion is located inside the formation region of the air holes when viewed in a direction perpendicular to the photonic crystal layer.