Thermal-Radiation Light Source With 2D Photonic Crystal for High-Speed Modulation
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Solution Overview
Problem
Conventional thermal emission sources have a low response speed for intensity modulation, making them unsuitable for sensors that require high-frequency noise removal, as they can only modulate light intensity at frequencies of approximately 1-100 Hz, necessitating external mechanical switching of the optical path.
Innovation Solution
A thermal emission source incorporating a two-dimensional photonic crystal with a slab structure of n-type and p-type semiconductor layers and modified refractive index areas, allowing for voltage-controlled modulation of light intensity by altering the energy levels in quantum wells, enabling high-frequency switching similar to photoelectric conversion elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional thermal emission sources are used for intensity modulation, then the device structure remains simple, but the response speed is limited to 1-100 Hz requiring external mechanical switching
Solution Approach 1:
The patent replaces the external mechanical switching system with an internal electric field control mechanism. By applying voltage to the quantum well structure, the energy levels are modulated directly, achieving intensity modulation at 1-100 kHz without mechanical moving parts. This substitution of mechanical control with electric field control resolves the contradiction between response speed and device complexity.
Solution Approach 2:
The patent changes the energy level parameters of the quantum well structure through voltage application. By modulating the electric field across the quantum wells, the energy separation between subbands changes, which directly controls the thermal emission intensity. This parameter change approach enables high-speed modulation while maintaining a simple device structure without mechanical components.
2Object-affected harmful factors
If broadband thermal emission is used, then the emission source can be simple, but unnecessary wavelengths cause heating of the measurement target and increase power consumption
Solution Approach 1:
The patent applies local quality by creating specific quantum well structures with defined energy gaps that correspond to particular infrared wavelengths. The quantum wells are designed with specific thicknesses and material compositions to emit only at desired wavelengths, while blocking unnecessary broadband radiation. This localized spectral control eliminates harmful heating effects while maintaining reasonable device complexity.
Solution Approach 2:
The patent introduces dynamic control of the emission spectrum through voltage-modulated quantum well energy levels. By changing the applied voltage, the energy separation in quantum wells changes, allowing dynamic selection of emission wavelengths. This dynamic spectral control enables the emission source to adapt to different measurement requirements while minimizing unnecessary thermal radiation.
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 solution allows for high-speed modulation of light intensity up to 1-100 kHz, suitable for sensors, and potentially 10-50 MHz for free-space communication, with controlled electric resistance and capacitance to optimize operation frequency and reduce unnecessary thermal emissions.
Implementation Method 1
a quantum well structure layer having a quantum well structure... a wavelength conversion layer having a function of converting a wavelength of incident light
Implementation Method 2
an energy transition occurs between the energy bands formed in the quantum well (for distinction from the energy bands of the semiconductor, those bands are called 'subbands'), whereby a range of wavelengths of light within a specific wavelength band are generated
Implementation Method 3
a two-dimensional photonic crystal... the light having a specific wavelength determined by the lattice constant of the photonic crystal resonates with the photonic crystal
Implementation Method 4
by enabling the formation of standing waves of that specific wavelength of light
Implementation Method 5
If a photoelectric conversion element which directly converts electric power into light (such as a laser diode) is used as the emission source, the infrared radiation having a rectangular waveform with the output of the infrared light repeatedly changed between the 'ON' and 'OFF' levels can be easily generated
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3C
AI summary
The present invention provides a thermal emission source capable of switching the intensity of light at a high response speed similarly to a photoelectric conversion element. A thermal emission source 10 includes: a two-dimensional photonic crystal 12 including a slab 11 in which an n-layer 112 made of an n-type semiconductor, a quantum well structure layer 114 having a quantum well structure, and a p-layer 111 made of a p-type semiconductor are stacked in the mentioned order in the thickness direction, wherein modified refractive index areas (air holes 121) whose refractive index differs from the refractive indices of the n-layer 112, the p-layer 111 and the quantum well structure layer 114 are cyclically arranged in the slab 11 so as to resonate with a specific wavelength of light corresponding to a transition energy between the subbands in a quantum well in the quantum well structure layer 114; and a p-type electrode 131 and an n-type electrode 132 for applying, to the slab 11, a voltage which is negative on the side of the p-layer 111 and positive on the side of the n-layer 112.