Surface-Emitting Photonic Crystal Laser for Uniform Current Injection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing surface-emitting photonic-crystal lasers (PCSELs) face challenges in achieving high beam quality due to inhomogeneous current injection, shadowing effects, and degradation of beam quality caused by absorption, light scattering, and filamentation in the waveguide.
Innovation Solution
The proposed solution involves a surface-emitting PCSEL design that includes an active layer sandwiched between first and second waveguide layers, where the second waveguide layer forms a 2D photonic crystal with periodically arranged regions of different refractive indices. This design enhances electromagnetic radiation scattering and interference, leading to improved beam quality and reduced lasing threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If electrical contacts are patterned on both sides of the active layer to outcouple electromagnetic radiation, then radiation outcoupling is improved, but inhomogeneous current impression and shadowing occur
Solution Approach 1:
The laser cavity is segmented into multiple independent microlasers arranged in an array, each microlaser forming its own optical mode. This segmentation allows current to be distributed uniformly across multiple smaller units rather than requiring large patterned contacts, eliminating shadowing effects while maintaining effective radiation outcoupling from the entire array surface.
Solution Approach 2:
The solution transitions from planar current injection to three-dimensional current distribution through vertical cavity design. The active layer is positioned between distributed Bragg reflectors (DBRs) that enable current injection from the bottom while radiation couples out through the top surface, separating current injection and radiation outcoupling pathways in the vertical dimension to avoid shadowing.
2Device complexity
If vias are provided through the waveguide layer to contact the active layer from one side, then contact complexity is reduced, but beam quality degrades due to absorption, light scattering, and filamentation
Solution Approach 1:
The harmful via structures are completely removed from the design. Instead of providing vias through the waveguide layer, the invention uses a planar contact structure where current is injected through the waveguide layer without penetrating it, eliminating the source of absorption, scattering, and filamentation that degrade beam quality.
Solution Approach 2:
The waveguide layer itself serves as an intermediary that allows current to reach the active layer without requiring physical penetration. The current flows laterally through the waveguide layer to contact the active layer, avoiding the need for vias that would create beam quality issues through absorption and scattering.
3Reliability
If the photonic crystal structure is implemented to scatter radiation, then beam quality is improved, but manufacturing complexity increases
Solution Approach 1:
The photonic crystal structure uses simple geometric parameters (hole diameter, pitch, depth) that can be directly controlled by standard semiconductor fabrication processes like electron beam lithography and reactive ion etching. By optimizing these parameters, high beam quality is achieved without requiring complex manufacturing steps, as the structure leverages existing fabrication capabilities.
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 described PCSEL design achieves high beam quality with reduced lasing threshold and improved wavelength-mode resonance, allowing for efficient electromagnetic radiation emission perpendicular to the crystal surface with monomodality and narrow radiation profiles.
Implementation Method 1
A lattice period may be selected to substantially coincide with a wavelength of the radiation generated by the active layer, or to substantially coincide with a multiple of that wavelength. In this way, the Bragg condition is satisfied in order to achieve 2D feedback in the plane of the photonic crystal and light emission perpendicular to it.
Implementation Method 2
The photonic crystal is configured to influence the electromagnetic radiation generated by the active layer. In particular, the photonic crystal scatters the radiation in the transversal direction.
Implementation Method 3
Scattered waves of electromagnetic radiation may interfere with each other and with the original wave in a constructive manner or a destructive manner.
Implementation Method 4
an active layer for generating electromagnetic radiation by charge carrier recombination
Implementation Method 5
The first and second waveguide layers form a waveguide into which the active layer is embedded. An optical wave is guided in the waveguide in a lateral direction.
Data Source
AI summary
The invention relates to a surface-emitting photonic crystal laser (1). The laser has an active layer for generating electromagnetic radiation by combining charge carriers, wherein the active layer has a first main surface and a second main surface lying opposite the first main surface. The first main surface is equipped with a first waveguide layer, and the second main surface is equipped with a second waveguide layer, said waveguide layers having regions which are arranged periodically relative to one another and additional regions which have different refractive indices and which form a photonic crystal. The first waveguide layer is equipped with a first casing layer which has at least one p-connection region for injecting electrically positive charge carriers into the active layer and at least one n-connection region for injecting electrically negative charge carriers into the active layer. The invention additionally relates to a method for producing a surface-emitting photonic crystal laser and to an optoelectronic system.