Electrically modulated light source

Abstract

The present application provides a kind of electrically modulated light source, which includes a carbon nanotube-graphene composite film structure, a first electrode and a second electrode, the first electrode and the second electrode are electrically connected with the carbon nanotube-graphene composite film structure respectively, the first electrode and the second electrode are used to load voltage to the carbon nanotube-graphene composite film structure, the electrically modulated light source is heated to the highest temperature in less than 10 milliseconds after loading voltage and emits incandescent light, it is cooled to its initial temperature in less than 10 milliseconds after removing voltage, and the modulation frequency of the electrically modulated light source is greater than or equal to 150 kHz.

Description

Technical Field

[0001] This invention relates to an electrically modulated light source. Background Technology

[0002] As global industrialization matures, industrial production releases large amounts of greenhouse gases and other pollutants into the environment. These gases not only cause rising Earth's surface temperatures but also pose a threat to human health. Therefore, detecting the levels of these gases in the environment and taking remedial measures is a major aspect of environmental protection. Gas systems, especially the atmosphere, require real-time quantitative detection, demanding stable performance, rapid response, and the ability to detect minute concentrations. Non-dispersive infrared (NDIR) spectrometers perfectly meet these requirements. They are simple in structure, allow for flexible component replacement, are low-cost, and possess high gas specificity. Once the absorption spectrum of a gas is measured, its sharp and narrow characteristic absorption peaks directly identify the gas type. Therefore, there is no gas cross-response, and real-time, on-site, and even remote measurements can be performed without interfering with the gas sample. Furthermore, NDIR spectrometers can determine the intensity of incident light, making the measurement self-referenced, thus ensuring high reliability and repeatability of the testing system.

[0003] Modulated light sources are widely used in NDIR spectrometers. NDIR spectrometers employing modulated light sources are popular and widely used due to their small size, high stability, and high testing accuracy. Compared with non-optical detection methods, NDIR spectroscopic detection methods using modulated light sources have higher sensitivity, selectivity, and stability; longer lifespan; relatively shorter reaction time; and the ability to achieve online real-time detection. Furthermore, their performance is not degraded by environmental changes or catalyst poisoning caused by specific gases.

[0004] Traditional modulation light sources include mechanical modulation sources, mid-infrared laser sources, lead-salt diode lasers, and nonlinear sources. However, mechanical modulation sources require high mechanical precision and time resolution, have slow modulation response, and are prone to affecting the optical path; mid-infrared laser sources lack the stability of continuous wavelengths; lead-salt diode lasers have low output power and high cooling requirements; and nonlinear sources are complex and have low power. These traditional modulation light sources limit the application of NDIR spectrometers. Summary of the Invention

[0005] In view of this, it is indeed necessary to provide an electrically modulated light source that can solve the above-mentioned technical problems.

[0006] An electrically modulated light source includes a carbon nanotube-graphene composite film structure, a first electrode, and a second electrode. The first and second electrodes are electrically connected to the carbon nanotube-graphene composite film structure, respectively. The first and second electrodes are used to apply a voltage to the carbon nanotube-graphene composite film structure. After the voltage is applied, the electrically modulated light source heats up to its maximum temperature and emits incandescent light within less than 10 milliseconds. After the voltage is removed, it cools down to its initial temperature within less than 10 milliseconds. The modulation frequency of the electrically modulated light source is greater than or equal to 150 kHz.

[0007] Compared to existing technologies, the electromodulated light source provided by this invention includes a carbon nanotube-graphene composite film structure. This carbon nanotube-graphene composite film structure can radiate a wide spectrum. Increasing the applied voltage of the carbon nanotube-graphene composite film structure or increasing the number of super-aligned carbon nanotube layers and their length along the current direction can increase its radiation power. Therefore, this electromodulated light source has flexible adjustability, is simple to operate, and does not affect the optical path. The electromodulated light source can achieve modulation frequencies of 150 kHz or even higher, and can rapidly heat up and cool down within approximately a few milliseconds or even hundreds of microseconds, exhibiting a rapid modulation response. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the structure of an electrically modulated light source provided in an embodiment of the present invention.

[0009] Figure 2 Scanning electron microscope (SEM) image of a carbon nanotube-graphene composite film structure provided in an embodiment of the present invention.

[0010] Figure 3 To be Figure 2 Scanning electron microscope (SEM) image obtained after local enlargement of the carbon nanotube-graphene composite film structure.

[0011] Figure 4 The electric modulation light source provided in this embodiment of the invention compares the radiation signal and pulse signal in two bands, 0.35-1.1 micrometers (μm) and 2.0-10.6 μm, when the pulse duty cycle is 50% and the frequency is 10 Hz. The horizontal axis represents time, and the vertical axis represents heating voltage and signal.

[0012] Figure 5 The curves showing the variation of radiation signal of carbon nanotube-graphene composite film structure in the 0.35-1.1μm band with time when the duty cycle of the pulse is 50% and the frequency is 20-500Hz are shown.

[0013] Figure 6The curves showing the variation of radiation signal of carbon nanotube-graphene composite film structure in the 0.35-1.1μm band with time when the duty cycle of the pulse is 50% and the frequency is 1k-50kHz are shown.

[0014] Figure 7 The curves showing the variation of radiation signal of carbon nanotube-graphene composite film structure in the 2.0-10.6μm band with time when the duty cycle of the pulse is 50% and the frequency is 20-500Hz are shown.

[0015] Figure 8 The curves showing the variation of radiation signal of carbon nanotube-graphene composite film structure in the 2.0-10.6μm band with time when the duty cycle of the pulse is 50% and the frequency is 1k-15kHz are shown.

[0016] Explanation of main component symbols

[0017] 100 Electric modulation light source

[0018] Carbon nanotube-graphene composite film structure 102

[0019] First electrode 104

[0020] Second electrode 106

[0021] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0022] The following will describe in further detail the electrically modulated light source, non-dispersive infrared spectroscopy detection system, and gas detection method provided by the present invention with reference to the accompanying drawings.

[0023] Please see Figure 1 The first embodiment of the present invention provides an electrically modulated light source 100. The electrically modulated light source 100 includes a carbon nanotube-graphene composite film structure 102, a first electrode 104, and a second electrode 106. By applying a voltage to both ends of the electrically modulated light source through the first electrode 104 and the second electrode 106, the electrically modulated light source can instantly heat up and emit thermal radiation after the voltage is applied, and can instantly cool down to its initial temperature after the voltage is removed. Instantaneous heating means that the time taken for the electrically modulated light source to reach its highest temperature from its initial temperature after the voltage is applied is on the order of milliseconds; instantaneous cooling means that the time taken for the electrically modulated light source to drop from its highest temperature to its initial temperature after the voltage is removed is also on the order of milliseconds. The millisecond level refers to a time less than 10 milliseconds.

[0024] The carbon nanotube-graphene composite film structure comprises at least one layer of carbon nanotube film and at least one layer of graphene film stacked together. The at least one layer of carbon nanotube film comprises multiple carbon nanotubes connected by van der Waals forces. The at least one layer of carbon nanotube film can be a thin film of super-aligned carbon nanotubes. The at least one layer of carbon nanotube film can be a structure composed solely of carbon nanotubes. The at least one layer of carbon nanotube film can include a single super-aligned carbon nanotube film, or multiple super-aligned carbon nanotube films stacked together. The graphene film can be a single, complete graphene film, or a film structure formed by overlapping multiple graphene films. In the carbon nanotube-graphene composite film structure, a graphene film is laid on the surface of the at least one layer of carbon nanotube film as a carrier to form the composite film structure. In this embodiment, the carbon nanotube-graphene composite film structure is obtained by laying four layers of vertically cross-laid superaligned carbon nanotube film on a copper foil with large crystalline domains grown on it, followed by etching the copper foil with ammonium sulfate solution. Figure 2 It can be observed that the macroscopic structure of the carbon nanotube-graphene composite film exhibits a very clear cross-network, and the structure of the composite film after heating also exhibits a clear cross-network; from Figure 3 A distinct morphology of cross-stacking carbon nanotube bundles can be observed, with a thin film at its base. This film is not intact but rather composed of graphene fragments with large crystalline domains grown on the copper foil, resulting in pores in the underlying film. The presence of graphene fills these pores in the superciliated carbon nanotube network, reducing its transmittance. Simultaneously, due to the extremely dense network on the surface of the superciliated carbon nanotube film, its reflectivity is very low, approaching zero. Therefore, depositing a graphene film on the surface of the superciliated carbon nanotube film can effectively increase its emissivity.

[0025] When the carbon nanotube-graphene composite film structure includes multiple layers of super-aligned carbon nanotube films, these multiple super-aligned carbon nanotube films are stacked. The intersection angle between the carbon nanotubes in two adjacent super-aligned carbon nanotube films can be any angle, preferably 90 degrees, so that the resulting carbon nanotube film structure is more stable and less prone to damage.

[0026] The superaligned carbon nanotube film is composed of a plurality of carbon nanotubes. These carbon nanotubes are preferentially oriented in essentially the same direction, meaning that the overall extension direction of most carbon nanotubes in the superaligned carbon nanotube film is essentially the same. Furthermore, the overall extension direction of most carbon nanotubes is essentially parallel to the surface of the superaligned carbon nanotube film. Of course, a small number of randomly arranged carbon nanotubes exist in the superaligned carbon nanotube film, but these do not significantly affect the overall orientation of the majority of carbon nanotubes in the superaligned carbon nanotube film. Therefore, the possibility of partial contact between parallel carbon nanotubes among the majority of carbon nanotubes extending in essentially the same direction in the superaligned carbon nanotube film cannot be ruled out.

[0027] The super-aligned carbon nanotube film can be fabricated over large areas, and by changing its structural size, number of layers, and the magnitude or frequency of the applied voltage, its radiant energy distribution can be altered to obtain light signals of different frequencies. Therefore, this carbon nanotube-graphene composite film structure has flexible tunability as an electrically modulated light source. Furthermore, in a vacuum environment, after energizing the carbon nanotube-graphene composite film structure, when the temperature of the structure reaches a certain level, it begins to radiate significant visible light, covering the wavelength range of 0.35-1.1 micrometers (UV-VIS-NIR) and 0.2-10.6 micrometers (NIR-MIR). The carbon nanotube-graphene composite film structure can reach temperatures of 1000K or even higher in a vacuum.

[0028] In this embodiment, a pulse with a 50% duty cycle was modulated onto the carbon nanotube-graphene composite film structure. The modulated signal at a peak temperature of 1066 K was detected using a mercury cadmium telluride detector and a silicon detector. The modulation frequency was 10 Hz. The two detectors could detect radiation in the wavelength ranges of 2.0-10.6 μm and 0.35-1.1 μm, respectively. For details on the radiation signals in these two wavelength ranges, please refer to [link to relevant documentation]. Figure 4 Calculations showed that in the 0.35–1.1 μm band, the rise and fall times were 2.00 ± 0.03 ms and 0.52 ± 0.04 ms, respectively; and in the 2.0–10.6 μm band, the rise and fall times were 2.01 ± 0.06 ms and 3.12 ± 0.37 ms, respectively. The radiation signal from the carbon nanotube-graphene composite film structure exhibits a rapid response to pulsed signals. In modulation experiments, the radiation signal under pulse modulation with frequencies ranging from 20 Hz to 50 kHz was studied; detailed results are available in […]. Figures 5 to 8With a fixed pulse duty cycle of 50% and a fixed peak voltage, the detector signal becomes very small at higher frequencies. This is especially true for uncooled MCT detectors, where the radiated signal becomes very small at high frequencies, resulting in significant noise in the detected signal. Therefore, in the 2.0-10.6μm band, only results up to 15kHz are shown.

[0029] Figure 4 For time-domain analysis, the response of the carbon nanotube-graphene composite film structure 102 to a pulse voltage, obtained using a Si detector and a mercury cadmium telluride (MCT) detector, is shown on an oscilloscope. Figure 4 It can be seen that the signals acquired by the Si detector in the UV-VIS-NIR band and the signals acquired by the MCT detector in the NIR-MIR band can be synchronized with the square wave pulse signal. Figure 4 It is explained that after the carbon nanotube-graphene composite film structure 102 is subjected to a voltage, the temperature of the carbon nanotube-graphene composite film structure 102 rises instantaneously and generates radiation. The energy of the radiation can be successfully detected by the Si detector and the mercury cadmium telluride (MCT) detector. Therefore, the carbon nanotube-graphene composite film structure 102 can be used as a modulated ultraviolet to visible and infrared light source.

[0030] Please see Figure 5 and Figure 6 This represents the radiation signal in the UV-VIS-NIR band obtained by the Si detector when the modulation frequency is 20-500Hz. Please refer to... Figure 7 and Figure 8 This represents the radiation signal in the NIR-MIR optical band obtained by the MCT detector when the modulation frequency is 20-500Hz. Figure 5-8 It can be seen that the superciliated carbon nanotube-graphene composite film structure can instantly heat up and emit thermal radiation after being subjected to a voltage, and can radiate a considerable and detectable periodic radiation signal. Moreover, after being subjected to a pulsed voltage, the carbon nanotube-graphene composite film structure can radiate a time-periodic optical signal synchronized with the modulation signal. Since both the superciliated carbon nanotube film and graphene exhibit light absorption properties over a very wide spectral range, they can also radiate light over a wide spectral range, thus the superciliated carbon nanotube-graphene composite film also possesses a wide-spectral radiation capability.

[0031] The electromodulated light source provided by this invention includes a carbon nanotube-graphene composite film structure. This carbon nanotube-graphene composite film structure can radiate a wide spectrum. Increasing the applied voltage of the carbon nanotube-graphene composite film structure or increasing the number of super-aligned carbon nanotube layers and their length along the current direction can increase its radiation power. Therefore, this electromodulated light source has flexible adjustability, is simple to operate, and does not affect the optical path. The electromodulated light source can achieve a modulation frequency greater than or equal to 150 kHz and can rapidly heat up and cool down within approximately a few milliseconds or even hundreds of microseconds, exhibiting a fast modulation response. Furthermore, the described electromodulated light source is a carbon nanotube-graphene composite film structure, which is very simple to prepare and can be rapidly fabricated on a large scale. It exhibits stable performance, is easy to store, and is very low in cost. Therefore, the electromodulated light source of this invention can be made in large sizes and is expected to be used as a broadband light source. For example, it can be used as an electromodulated light source in non-dispersive infrared gas monitoring. By using multiple narrowband filters of different wavelengths, various different gases can be tested. If filters of different wavelengths are used, light sources that meet the requirements of different wavelengths can be constructed. The carbon nanotube-graphene composite film structure can reach very high temperatures in a vacuum, and the electromodulation frequency of this electromodulated light source can reach 150kHz or even higher, which is difficult to achieve with existing electromodulated thermal radiation light sources.

[0032] The electromodulated light source of the present invention has a wide range of applications. For example, it can be used as a high-frequency modulated light source to replace optical detection methods that require mechanical modulation such as choppers; it can also be used for gas detection in non-dispersive infrared spectroscopy detection methods; it can also be used as a light source in Fourier transform infrared spectrometers or other occasions to test the properties of samples, such as absorption spectra, transmission and reflection; it can also be prepared into a light source array; or graphene can be combined with other thin films, such as ultrathin metal films, dielectric films, etc., to construct a graphene-based thin film thermal radiation light source.

[0033] Furthermore, those skilled in the art may make other changes within the spirit of this invention. Of course, all such changes made in accordance with the spirit of this invention should be included within the scope of protection claimed by this invention.

Claims

1. An electrically modulated light source, characterized by The electrically modulated light source comprises a carbon nanotube-graphene composite film structure, a first electrode and a second electrode, the first electrode and the second electrode are electrically connected with the carbon nanotube-graphene composite film structure respectively, the first electrode and the second electrode are used to load voltage to the carbon nanotube-graphene composite film structure, the electrically modulated light source is heated to the highest temperature and emits incandescent light in less than 10 milliseconds after loading voltage, is cooled to the initial temperature in less than 10 milliseconds after removing voltage, and the modulation frequency of the electrically modulated light source is greater than or equal to 150 kHz.

2. An electrically modulated light source as claimed in claim 1, characterized in that The carbon nanotube-graphene composite film structure comprises at least one layer of carbon nanotube film and at least one layer of graphene film.

3. An electrically modulated light source as claimed in claim 2, characterized in that In the carbon nanotube-graphene composite film structure, the graphene film is laid on the surface of the at least one layer of carbon nanotube film to form the composite film structure.

4. An electrically modulated light source as claimed in claim 2, characterized in that the light source is a light emitting diode. The at least one layer of carbon nanotube film comprises a plurality of layers of super-aligned carbon nanotube film stacked and laid, and the intersection angle between the carbon nanotubes in the super-aligned carbon nanotube film of adjacent two layers is equal to 90 degrees.

5. An electrically modulated light source as claimed in claim 2, characterized in that the light source is a light emitting diode. The at least one layer of carbon nanotube film in the carbon nanotube-graphene composite film structure comprises 10 layers of super-aligned carbon nanotube film stacked.

6. An electrically modulated light source as claimed in claim 2, characterized in that The at least one layer of graphene film is a layer of complete graphene film.

7. An electrically modulated light source as claimed in claim 2, characterized in that the light source is a light emitting diode. The at least one layer of graphene film comprises a plurality of layers of graphene mutually overlapped.

8. The electrically modulated light source of claim 1, wherein, In the temperature range of 800-1200℃, in the visible light band, the rise time of the carbon nanotube-graphene composite film structure after loading voltage is 3-4 milliseconds, and the fall time of the carbon nanotube-graphene composite film structure after removing voltage is 600 microseconds-1 millisecond.

9. The electrically modulated light source of claim 1, wherein, In the temperature range of 800-1200℃, in the infrared light band, the rise time of the carbon nanotube-graphene composite film structure after loading voltage is 2-3 milliseconds, and the fall time of the carbon nanotube-graphene composite film structure after removing voltage is 5 milliseconds.

10. The electrically modulated light source of claim 1, wherein, In a vacuum environment, when the temperature of the carbon nanotube-graphene composite film structure reaches a certain value, the carbon nanotube-graphene composite film structure starts to radiate visible light, and the detected band covers 0.35-1.1 microns and 0.2-10.6 microns.

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