Terahertz Laser Surface Emission via Asymmetric Photonic Crystal
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Solution Overview
Problem
Existing semiconductor laser devices struggle to efficiently emit terahertz waves as plane waves, requiring complex optical configurations and large external forms due to the need for collimator lenses in edge-emitting lasers.
Innovation Solution
A semiconductor laser device with a stacked active layer, a first layer featuring a two-dimensional lattice of asymmetric pits, and a surface metal film with openings that emit terahertz waves perpendicularly, utilizing a periodic-structure photonic crystal to achieve high-efficiency plane wave emission without the need for collimator lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an edge emitting quantum cascade laser is used as the light source, then laser oscillation in the terahertz range is achieved, but a collimator lens is necessary causing the exterior form to become large
Solution Approach 1:
The patent extracts and eliminates the collimator lens from the optical configuration by transitioning from edge-emitting to surface-emitting laser architecture. The photonic crystal structure integrated into the active layer directly emits collimated terahertz waves without requiring external optical components, thereby reducing device complexity and exterior form.
Solution Approach 2:
The patent merges the photonic crystal structure with the active layer to create an integrated surface-emitting quantum cascade laser. This combination allows the laser to emit terahertz waves in a direction perpendicular to the active layer with inherent beam collimation, eliminating the need for separate collimator lenses and reducing overall device complexity.
2Reliability
If an edge emitting quantum cascade laser is used, then terahertz laser oscillation is achieved, but the device requires a collimator lens resulting in large exterior form
Solution Approach 1:
The patent replaces the mechanical optical system (collimator lens) with a photonic crystal structure that provides inherent beam collimation through its periodic refractive index modulation. This substitution achieves plane wave emission with high reliability while eliminating the need for external optical components and reducing device exterior form.
3Productivity
If conventional laser emission is used, then laser light is emitted, but optical components are required increasing device complexity
Solution Approach 1:
The patent implements self-service by designing the photonic crystal structure to inherently provide beam collimation and directional emission. The periodic structure self-organizes the emitted terahertz waves into plane waves without requiring external optical components, thereby maintaining high emission efficiency while reducing device complexity.
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
Enables the efficient emission of terahertz waves as plane waves with high transmittance and reduced optical complexity, allowing for a compact device design and improved detection accuracy of fine particles by shifting resonant frequencies.
Implementation Method 1
Multiple quantum well layers are stacked in the active layer 25; and the active layer 25 is configured to emit laser light 60 of a terahertz wave by an intersubband transition
Implementation Method 2
The first layer 27 is provided on the active layer 25 and has a first surface 21a in which multiple pits 101 are provided to form a two-dimensional lattice
Data Source
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AI summary
A semiconductor laser device of an embodiment includes an active layer, a first layer, and a surface metal film. Multiple quantum well layers are stacked in the active layer; and the active layer is configured to emit laser light of a terahertz wave by an intersubband transition. The first layer is provided on the active layer and has a first surface in which multiple pits are provided to form a two-dimensional lattice. The surface metal film is provided on the first layer and has multiple openings. Each of the pits is asymmetric with respect to a line parallel to a side of the lattice. The laser light passes through the multiple openings and is emitted in a direction substantially perpendicular to the active layer.