Terahertz Quantum Cascade Laser With Dual Distributed Feedback
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Solution Overview
Problem
Generating terahertz waves using high-frequency circuits is challenging due to complex configurations, and existing technologies lack simple, room temperature, broadly tunable, electrically pumped semiconductor sources in the terahertz spectral range.
Innovation Solution
A terahertz quantum cascade laser device with a semiconductor stacked body and distributed feedback regions, where the active layer emits infrared laser light through intersubband optical transitions, and the device includes a ridge waveguide and electrodes to generate terahertz waves as difference frequency waves from dual-wavelength infrared laser light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a KTP-OPO and nonlinear crystal configuration is used to generate terahertz waves, then terahertz wave generation is achieved, but the device configuration becomes complex
Solution Approach 1:
The patent merges multiple functions into a single quantum cascade laser device. The active layer generates both infrared laser light wavelengths simultaneously, and the nonlinear optical effect within the same device structure produces terahertz waves, eliminating the need for separate KTP-OPO and nonlinear crystal components.
Solution Approach 2:
The quantum cascade laser active layer performs multiple functions: it generates infrared laser light at two different wavelengths through intersubband transitions, and simultaneously serves as the nonlinear optical medium for terahertz wave generation through difference frequency generation, making the device universally functional for both infrared and terahertz applications.
2Ease of operation
If dual-wavelength infrared laser light is generated from KTP-OPO and irradiated on nonlinear crystal, then terahertz waves are generated as difference frequency waves, but the configuration is complex
Solution Approach 1:
The patent combines the infrared laser generation and terahertz difference frequency generation functions into a single integrated quantum cascade laser device, where the active layer produces both infrared wavelengths and the nonlinear optical conversion occurs within the same structure, greatly simplifying operation.
Solution Approach 2:
The quantum cascade laser device is self-sufficient by generating both required infrared wavelengths internally through intersubband transitions in the active layer, and automatically performing the difference frequency generation to produce terahertz waves without requiring external KTP-OPO systems or separate nonlinear crystal irradiation setups.
3Ease of manufacture
If high frequency circuit is used to generate terahertz waves, then terahertz wave generation is attempted, but it is difficult to generate due to technical challenges
Solution Approach 1:
The patent replaces the mechanical/electrical high frequency circuit approach with an optical-based quantum cascade laser system. The active layer uses quantum mechanical intersubband transitions to generate infrared laser light, which then undergoes nonlinear optical difference frequency generation to produce terahertz waves, achieving more reliable generation through optical quantum effects rather than electrical circuit limitations.
4Adaptability or versatility
If room temperature, broadly tuneable, electrically pumped semiconductor sources are used in terahertz spectral range, then operation simplicity similar to diode lasers is achieved, but such sources are highly desired indicating they don't currently exist
Solution Approach 1:
The patent introduces dynamic tunability by making the terahertz wave generation wavelength可调 through electrical current control. By adjusting the injection current in the quantum cascade laser active layer, the wavelengths of generated infrared laser light change, which in turn adjusts the difference frequency and thus the terahertz output wavelength, enabling broadly tuneable operation.
Solution Approach 2:
The patent utilizes parameter changes in the quantum cascade laser active layer to achieve broad tunability. By changing operational parameters such as injection current and temperature, the intersubband transition wavelengths shift, which changes the difference frequency generated through nonlinear optical effects, thereby tuning the terahertz output across a broad spectral range.
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 device efficiently generates terahertz waves with improved tunability and power consumption control, enabling effective detection of substances like those inside a paper bag, with enhanced temperature control and wavelength tuning capabilities.
Implementation Method 1
The active layer is provided on the substrate and is configured to emit first infrared laser light G1 and second infrared laser light G2 by an intersubband optical transition
Implementation Method 2
A terahertz wave is generated as a difference frequency wave when dual-wavelength infrared laser light is generated from a KTP (KTiOP4)-OPO (Optical Parametric Oscillator) and irradiated on a nonlinear crystal
Implementation Method 3
a KTP (KTiOP4)-OPO (Optical Parametric Oscillator)
Implementation Method 4
A first distributed feedback region and a second distributed feedback region are provided at an upper surface of the first clad layer
Implementation Method 5
A ridge waveguide is provided in the semiconductor stacked body
Data Source
Figure 1A~1C
Figure 2~3B
Figure 4A~4C
AI summary
A terahertz quantum cascade laser device includes a substrate (10), q semiconductor stacked body (20) and a first electrode (30). The semiconductor stacked body (20) includes an active layer (12) and a first clad layer (14). The active layer (12) is provided on the substrate (10) and is configured to emit infrared laser light by an intersubband optical transition. The first clad layer (14) is provided on the active layer (12). A ridge waveguide (40) is provided in the semiconductor stacked body (20). A first distributed feedback region (14a) and a second distributed feedback region (14b) are provided at an upper surface of the first clad layer (14) to be separated from each other along an extension direction of the ridge waveguide (40). The first electrode (30) is provided at the upper surface of the first clad layer (14). A planar size of the first distributed feedback region (14a) is smaller than a planar size of the second distributed feedback region (14b).