Window-Shaped Electrode for 2D Photonic Crystal Laser Side Lobe Elimination
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Solution Overview
Problem
Conventional two-dimensional photonic crystal surface-emitting laser light sources suffer from the presence of unwanted side lobes due to the blocking effect of electrodes, which obstruct the emission of laser light and lead to constructive interference, and there is a lack of materials that are both transparent and efficient for electric charge injection.
Innovation Solution
A two-dimensional photonic crystal surface-emitting laser light source design featuring a transparent substrate, a two-dimensional photonic crystal located between the substrate and the active layer, a window-shaped electrode on the upper surface to allow laser light to pass through, and a smaller mount surface electrode closer to the active layer to increase current density and heat dissipation, along with an optional reflector to enhance emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an electrode is used to inject electric charges into the active layer, then electric charge injection efficiency is improved, but the electrode blocks laser light emission and causes side lobes to appear
Solution Approach 1:
The electrode structure is segmented into two separate electrodes: a first electrode positioned closer to the active layer for efficient charge injection, and a second electrode positioned farther away with a window to allow laser light emission. This segmentation resolves the contradiction by separating the charge injection function from the light emission path, eliminating side lobes while maintaining injection efficiency.
2Object-generated harmful factors
If a transparent material is used for the electrode to allow light passage, then side lobes are prevented, but electric charge injection efficiency deteriorates
Solution Approach 1:
Instead of using a single transparent electrode that compromises injection efficiency, the system uses two separate electrodes. The first electrode (closer to active layer) can be opaque and highly efficient for charge injection, while the second electrode (farther away) has a window for light emission. This resolves the contradiction by allowing opaque materials for injection while preventing side lobes through the windowed second electrode.
Solution Approach 2:
The solution moves the light emission function to a different spatial dimension by placing the windowed second electrode at a distance from the active layer. The window is positioned in a plane that does not obstruct the primary light emission path from the active layer, allowing transparent electrode behavior at the injection interface while maintaining light passage capability.
3Use of energy by moving object
If the electrode area is increased to improve charge injection, then injection efficiency is improved, but the blocking effect increases and side lobes become more prominent
Solution Approach 1:
The total electrode area is divided between two separate electrodes. The first electrode can have a larger area for efficient charge injection, while the second electrode has a controlled window area that allows light emission without causing significant blocking. This segmentation allows the injection electrode to be large without proportionally increasing the blocking effect on the light emission path.
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 eliminates side lobes by allowing laser light to pass through the window-shaped electrode, increases emission intensity by concentrating electric current and heat dissipation, and improves extraction efficiency with the reflector, resulting in higher emission efficiency compared to conventional designs.
Implementation Method 1
The periodic structure causes a Bragg diffraction within the crystal and produces an oscillation of laser light by amplifying light of a predetermined wavelength
Implementation Method 2
a window-shaped electrode on the upper surface to allow laser light to pass through
Implementation Method 3
an optional reflector to enhance emission efficiency
Data Source
AI summary
A two-dimensional photonic crystal surface-emitting laser light source producing a beam without side lobes is provided. A window-shaped electrode having a central window devoid of the electrode material is provided on a device substrate. A mount surface electrode smaller than the electrode including the window is provided on a mount surface. The distance between the substrate and the active layer is larger than that between the mount surface and the active layer. When a voltage is applied, electric charges are injected into the active layer and emission is obtained. Light having a specific wavelength is amplified by a two-dimensional photonic crystal and extracted through the window without side lobes due to interference. The positioning of the active layer close to the mount surface significantly enhances the heat-radiating effect.