Multi-Wavelength Thermal Radiation Light Source with Quantum Wells
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Solution Overview
Problem
Existing thermal radiation light sources are unable to generate multiple wavelengths simultaneously, which is necessary for detecting various gas components in exhaust gases, such as ammonia and nitrous oxide, as they typically produce light of only one wavelength, requiring expensive detectors or slow wavelength switching.
Innovation Solution
A thermal radiation light source with multiple quantum well structure layers and a photonic crystal portion that allows for the generation and switching of multiple wavelengths by adjusting the voltage applied to each quantum well structure layer, enabling fast wavelength switching and emission of specific wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a thermal radiation light source uses a single quantum well structure with photonic crystal, then light of one specific wavelength is amplified and generated, but it cannot generate multiple wavelengths simultaneously which are needed for detecting various gas components
Solution Approach 1:
The patent divides the quantum well structure into multiple independent quantum well layers (first quantum well layer, second quantum well layer, etc.), each capable of generating light at different wavelengths. This segmentation allows the system to generate multiple wavelengths simultaneously without requiring a completely separate light source for each wavelength, thus improving versatility while controlling complexity.
Solution Approach 2:
The photonic crystal structure serves multiple functions: it amplifies light from different quantum well layers at different wavelengths simultaneously, and it can be configured with different periodic structures (first photonic crystal with first period, second photonic crystal with second period) to support multiple wavelength amplifications. This multi-functionality enables a single device to handle multiple detection wavelengths.
2Object-affected harmful factors
If the light source emits broadband infrared radiation, then all wavelength ranges are covered, but unnecessary wavelengths irradiate the measurement target causing heating effects
Solution Approach 1:
Each quantum well layer is designed with specific properties to emit at particular wavelengths (different transition energies between subbands). The photonic crystal structures are configured with specific periodicities to amplify only the wavelengths corresponding to each quantum well layer. This local quality control ensures that only necessary wavelengths are emitted and amplified, preventing unnecessary heating of the measurement target.
Solution Approach 2:
The patent uses multiple quantum well layers that are structurally similar but tuned to different wavelengths, effectively creating 'copies' of the quantum well-photonic crystal system for each desired wavelength. This allows selective emission of specific wavelengths without requiring a completely different emission mechanism for each wavelength.
3Adaptability or versatility
If a detector capable of identifying multiple wavelengths is used, then various gas components can be detected simultaneously, but such detectors are expensive
Solution Approach 1:
The patent enables dynamic control of wavelength emission by independently controlling multiple quantum well layers. Each quantum well layer can be activated or deactivated, allowing the light source to dynamically switch between different wavelength emissions. This dynamic capability allows the use of simpler, less expensive detectors that detect intensity at a single wavelength, while the system provides multi-wavelength functionality through temporal or selective activation of different quantum well layers.
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 generation of multiple wavelengths at high speed, allowing for efficient detection of different gas components using inexpensive detectors that do not identify wavelengths, thereby improving detection efficiency and reducing costs.
Implementation Method 1
when heat is supplied from a heat source, a transition (intersubband transition) occurs between a plurality of discrete energy levels (subbands) formed in a quantum well having a quantum well structure. Light emission having a finite bandwidth centered on the wavelength corresponding to the transition energy occurs.
Implementation Method 2
the photonic crystal includes a periodic refractive index distribution and is capable of forming a standing wave of light having a specific wavelength corresponding to the period. In the photonic crystal provided with the quantum well structure, light having one wavelength determined by the period of the photonic crystal resonates and is amplified.
Implementation Method 3
light having one wavelength determined by the period of the photonic crystal resonates and is amplified
Implementation Method 4
By turning ON/OFF the application of this voltage, the number of electrons or positive holes in the quantum well can be changed, whereby the intensity of the light having the specific wavelength can be controlled.
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3(a)~3(b)
AI summary
A thermal radiation light source 10 includes a laminated body (10S) including m quantum well structure layers (111, 112) laminated where m is an integer of 2 or more, and including an n-layer (121, 122) and a p-layer (13) sandwiching each of the quantum well structure layers from both sides in the laminating direction wherein the n-layer is made of an n-type semiconductor and the p-layer is made of a p-type semiconductor; a voltage applying unit (151, 152) that is provided for each of the m quantum well structure layers and is directly or indirectly connected to the n-layer and the p-layer sandwiching each quantum well structure layer and that applies a voltage for moving to the n-layers or the p-layer a charge in a quantum well of each quantum well structure layer; a voltage switching unit (161, 162, 17) that switches ON/OFF of application of the voltage to each of the m quantum well structure layers; and a photonic crystal portion (20) disposed in the laminated body or adjacent to the laminated body, and formed so that lights of m kinds of wavelengths resonate, each of the lights of the m wavelengths being generated in each of the m quantum well structure layers corresponding to transition energy between subbands in the quantum well of the quantum well structure layer. The thermal radiation light source 10 can generate a plurality of wavelengths by switching the plurality of wavelengths one by one at a high speed.