A terahertz waveform detection system for air ionization to generate a residual current

Abstract

The present application relates to the technical field of optical detection analysis, and discloses a terahertz waveform detection system for generating residual current by air ionization, comprising: a femtosecond laser generation module for emitting strong femtosecond laser pulse to ionize gas-phase medium; a terahertz wave generation module for emitting terahertz test pulse to drive electron to generate residual current; a control module for changing the time delay between the femtosecond laser pulse and the terahertz pulse; a current detection module for detecting the residual current under different time delays; an acquisition module for recording the residual current under different time delays and reconstructing the time-domain waveform of the terahertz pulse; and a display module for displaying the time-domain waveform of the terahertz according to the reconstruction result of the acquisition module. The present application realizes the reconstruction of the time-domain waveform of the test pulse by detecting the change of the residual current with the time delay between the detection pulse and the test pulse, thereby realizing the detection of the time-domain waveform of the narrow-pulse-width terahertz pulse by the wide-pulse-width femtosecond pulse.

Description

Technical Field

[0001] This invention relates to the field of optical detection and analysis technology, and in particular to a terahertz waveform detection system that generates residual current by air ionization. Background Technology

[0002] Terahertz waves lie between the far-infrared and submillimeter waves, in a frequency band between macroscopic electronics and microscopic optoelectronics. They occupy a unique position in the electromagnetic spectrum and are characterized by low radiation energy, high signal-to-noise ratio, and wide bandwidth. Their optical properties offer unique advantages in detection and analysis applications.

[0003] Pump-probe technology uses two femtosecond pulses with a time delay to excite and probe the sample, respectively. The higher-energy, earlier-timed pulse is used as the pump light, and the lower-energy, later-timed pulse is used as the probe light. The pump light excites the sample to an excited state, and then the time-delayed probe light arrives to probe the evolution of the excited sample over time.

[0004] Optically pumped terahertz (OPTP) detection is a promising new technique for studying ultrafast carrier dynamics, developed from pump-probe technology. Unlike pump-probe technology, OPTP replaces the femtosecond pulses used for detection with terahertz pulses. Because terahertz pulses are highly sensitive to carrier distribution and changes on the semiconductor surface and phonon-related processes within the semiconductor when transmitted through a semiconductor sample, they are well-suited for probing the dynamic evolution of carriers and phonons in semiconductors. Compared to conventional pump-probe technology, OPTP is more sensitive to carrier and phonon information within semiconductors. OPTP can observe a richer variety of dynamic processes within semiconductor materials.

[0005] However, current terahertz detection technologies are mainly divided into coherent and incoherent detection technologies. Coherent detection technologies include electro-optic sampling, air breakdown coherent detection, air bias coherent detection, and photoconductive antennas. Coherent detection can detect the amplitude and phase information of terahertz waves, obtaining the time-domain waveform of the terahertz pulse. However, existing detection technologies often require the detection pulse width to be narrower than the pulse width to be measured.

[0006] Therefore, there is an urgent need to invent a terahertz waveform detection method that does not require the probe pulse to be narrower than the pulse to be measured, so as to reconstruct the time-domain waveform of the terahertz pulse to be measured. Summary of the Invention

[0007] The purpose of this invention is to provide a terahertz waveform detection system that generates residual current through air ionization. Based on the fact that the residual current generated by electrons produced by the ionization of the gas phase medium by the femtosecond laser probe pulse and the terahertz pulse under test are different under different time delays, the system achieves super-time resolution reconstruction of the time domain waveform of the terahertz pulse under test, thereby avoiding the limitation of the traditional requirement that the probe pulse be narrower than the pulse under test.

[0008] This invention provides a terahertz waveform detection system for residual current generated by air ionization, comprising:

[0009] Femtosecond laser generator module, used to emit high-intensity femtosecond laser probe pulses to ionize gaseous media;

[0010] Terahertz wave generator module, used to emit terahertz pulses to drive electrons to generate residual current;

[0011] The control module, connected to the femtosecond laser generating module, is used to adjust the time delay between the high-intensity femtosecond laser detection pulse and the terahertz test pulse;

[0012] The current detection module is used to detect the residual current generated after air ionization;

[0013] The acquisition module, electrically connected to the current detection module, is used to record the residual current under different time delays and reconstruct the time-domain waveform of the terahertz pulse.

[0014] The display module, electrically connected to the acquisition module, is used to display the time-domain waveform of the terahertz pulse under test reconstructed by the acquisition module.

[0015] Furthermore, the femtosecond laser generating module includes:

[0016] The laser emitting unit is used to emit high-intensity femtosecond laser pulses;

[0017] A polarization unit, connected to the laser emitting unit, is used to adjust the vibration direction of the high-intensity femtosecond laser detection pulse.

[0018] Furthermore, when the polarization unit is used to adjust the polarization direction of the high-intensity femtosecond laser probe pulse, it includes:

[0019] The polarization unit is used to adjust the polarization direction of the high-intensity femtosecond laser detection pulse. The horizontal polarization is adjusted to the vertical polarization using a half-wave plate, so that the polarization directions of the femtosecond laser detection pulse and the terahertz pulse under test are perpendicular to each other.

[0020] Furthermore, when the control module is used to change the time delay between the high-intensity femtosecond laser probe pulse and the terahertz test pulse, it includes:

[0021] The control module is used to acquire the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse, the duration T1 of the strong femtosecond laser detection pulse and the duration T2 of the terahertz test pulse, and to adjust the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse according to the duration T1 of the strong femtosecond laser detection pulse and the duration T2 of the terahertz test pulse.

[0022] Furthermore, when adjusting the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse based on the duration T1 of the strong femtosecond laser detection pulse and the duration T2 of the terahertz test pulse, the adjustment includes:

[0023] The control module is also used to preset the adjustment range T of the time delay τ between the terahertz test pulse and the strong femtosecond laser detection pulse, where T = T1 + T2;

[0024] The control module is also used to continuously increase the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse according to a preset adjustment range T;

[0025] When τ≤T, the current detection module adjusts the time delay τ once every time it completes a measurement of the remaining current under the current time delay.

[0026] When τ > T, stop adjusting the time delay τ;

[0027] When the time delay τ is adjusted, the control module can enable the terahertz pulse to completely sweep across the strong femtosecond laser pulse, thereby adjusting the time delay τ between the strong femtosecond laser detection pulse and the terahertz pulse to be measured.

[0028] This invention discloses a terahertz waveform detection system for generating residual current through air ionization. Compared with existing technologies, its advantages lie in the following: Firstly, by using a femtosecond laser generation module and a terahertz wave generation module, a wide-pulse-width, high-intensity femtosecond laser probe pulse can be generated to ionize the gaseous medium, producing a narrow-pulse-width terahertz test pulse to drive electrons and generate residual current. Simultaneously, a current detection module can detect this residual current. Secondly, the key role of the control module is to change the time delay between the femtosecond laser pulse and the terahertz pulse. The acquisition module utilizes the different residual currents detected by the current detection module under different time delays to reconstruct the time-domain waveform of the terahertz pulse. Finally, the display module provides an intuitive way to visually display the time-domain waveform of the terahertz pulse, enabling users to more clearly understand and analyze this waveform data. This innovative method allows for accurate and high-resolution reconstruction of the time-domain waveform of the terahertz pulse without requiring excessively wide probe pulses. This allows users to directly obtain the time-domain waveform of the terahertz pulse, helping to solve the problems caused by limitations in probe pulse width and providing a powerful tool for waveform analysis. Attached Figure Description

[0029] Figure 1 This is a structural block diagram of a terahertz waveform detection system for generating residual current through air ionization, according to an embodiment of the present invention. Detailed Implementation

[0030] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] like Figure 1As shown, an embodiment of the present invention provides a terahertz waveform detection system for generating residual current through air ionization, comprising: a femtosecond laser generation module, a terahertz wave generation module, a control module, a current detection module, an acquisition module, and a display module. The femtosecond laser generation module emits a strong femtosecond laser detection pulse to ionize the gaseous medium. The terahertz wave generation module emits a terahertz pulse to be measured to drive electrons and generate residual current. The control module, connected to the femtosecond laser generation module, adjusts the time delay between the strong femtosecond laser detection pulse and the terahertz pulse to be measured. The current detection module detects the residual current generated after air ionization. The acquisition module, electrically connected to the current detection module, records the residual current under different time delays and reconstructs the time-domain waveform of the terahertz pulse. The display module, electrically connected to the acquisition module, displays the time-domain waveform of the terahertz pulse to be measured reconstructed by the acquisition module.

[0032] Understandably, the system generates strong femtosecond laser probe pulses and terahertz wave pulses through the femtosecond laser generation module and the terahertz wave generation module, while the current detection module captures and quantifies the gaseous medium's response to these pulses, including the generated residual current. The control and acquisition modules determine the time-domain waveform of the terahertz pulse based on information provided by the current detection module at different time delays, achieving super-time-resolved waveform reconstruction. This is extremely helpful for studying the interaction between terahertz waves and electrons in air plasma. Finally, the display module allows users to intuitively observe and analyze the time-domain waveform of the terahertz pulse, providing crucial information about terahertz waves and helping scientists, researchers, and engineers gain a deeper understanding of their properties. This system can be applied to various fields, including materials science, optoelectronics, waveform analysis, and terahertz technology research, contributing to solving related problems and advancing scientific research.

[0033] Specifically, in some embodiments of the present invention, the femtosecond laser generating module includes a laser emitting unit and a polarization unit. The laser emitting unit is used to emit strong femtosecond laser pulses. The polarization unit is connected to the laser emitting unit and is used to adjust the polarization direction of the strong femtosecond laser pulses.

[0034] Specifically, when the polarization unit is used to adjust the polarization direction of a strong femtosecond laser pulse, it includes: adjusting the polarization direction of the strong femtosecond laser pulse, using a half-wave plate to adjust the horizontal polarization to the vertical polarization, so that the polarization directions of the femtosecond laser probe pulse and the terahertz pulse to be measured are perpendicular to each other.

[0035] Understandably, the polarization unit can adjust the polarization direction of a strong femtosecond laser pulse, making the polarization direction of the femtosecond laser pulse perpendicular to that of the terahertz pulse. This is helpful for signal measurement.

[0036] Specifically, in some embodiments of the present invention, when the control module is used to adjust the time delay between the strong femtosecond laser detection pulse and the terahertz test pulse, the control module is used to acquire the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse, the duration T1 of the strong femtosecond laser detection pulse and the duration T2 of the terahertz test pulse, and adjust the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse according to the duration T1 of the strong femtosecond laser detection pulse and the duration T2 of the terahertz test pulse.

[0037] Specifically, when the control module adjusts the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse according to the duration T1 of the strong femtosecond laser detection pulse and the duration T2 of the terahertz test pulse, the adjustment includes: the control module is further configured to preset the adjustment range T of the time delay τ between the terahertz test pulse and the strong femtosecond laser detection pulse, T = T1 + T2; the control module is further configured to continuously increase the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse according to the preset adjustment range T.

[0038] When τ≤T, the current detection module adjusts the time delay τ once every time it completes the measurement of the residual current under the current time delay.

[0039] When τ > T, stop adjusting the time delay τ;

[0040] When the time delay τ is adjusted, the control module can achieve a complete sweep of the terahertz pulse over the strong femtosecond laser pulse, thereby adjusting the time delay τ between the strong femtosecond laser detection pulse and the terahertz pulse to be measured.

[0041] Understandably, the electrical connection between the current detection module and the control module, and the electrical connection between the acquisition module and the current detection module, enables real-time data acquisition. This process ensures that the residual current intensity generated by the combined action of the terahertz pulse and the femtosecond laser pulse at different time delays can be recorded promptly and accurately. Secondly, the acquisition module is crucial in the experiment. It utilizes the residual current intensity data obtained from the current detection module to perform complex data processing and analysis to reconstruct the time-domain waveform of the terahertz pulse. This process is automated, efficiently processing large amounts of data and deriving accurate time-domain waveform information based on the analysis results. Automated data acquisition and analysis reduce the burden on the experimenter, minimize potential human error, and improve the repeatability and reliability of the experiment.

[0042] In summary, this invention provides a terahertz waveform detection system that generates residual current through air ionization. It utilizes a femtosecond laser generation module and a terahertz wave generation module to generate wide-pulse-width, high-intensity femtosecond laser pulses and narrow-pulse-width terahertz pulses. Simultaneously, a current detection module captures and quantifies the residual current generated after these pulses interact with the gaseous medium. Secondly, the key role of the control module is to change the time delay between the femtosecond laser pulse and the terahertz pulse. The acquisition module utilizes the different residual currents detected by the current detection module under different time delays to reconstruct the time-domain waveform of the terahertz pulse. Finally, the display module provides an intuitive way to visually represent the time-domain waveform of the terahertz pulse, enabling users to more clearly understand and analyze this waveform data. This innovative method allows for accurate and time-resolved reconstruction of the terahertz time-domain waveform without requiring excessively wide detection pulses. This allows users to directly obtain the time-domain waveform of the terahertz pulse, helping to solve the problems caused by limitations in detection pulse width and providing a powerful tool for waveform analysis.

[0043] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0044] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0045] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The function specified in one or more boxes.

[0046] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A terahertz waveform detection system for generating residual current through air ionization, characterized in that, include: Femtosecond laser generator module, used to emit high-intensity femtosecond laser probe pulses to ionize gaseous media; Terahertz wave generator module, used to emit terahertz pulses to drive electrons to generate residual current; Wherein, the pulse width of the high-intensity femtosecond laser detection pulse is wider than the pulse width of the terahertz pulse to be measured; A control module is connected to the femtosecond laser generating module, and the control module is used to adjust the time delay between the high-intensity femtosecond laser detection pulse and the terahertz test pulse; The current detection module is used to detect the residual current generated after air ionization; The acquisition module, electrically connected to the current detection module, is used to record the residual current under different time delays and reconstruct the time-domain waveform of the terahertz pulse. The display module, electrically connected to the acquisition module, is used to display the time-domain waveform of the terahertz pulse reconstructed by the acquisition module.

2. The terahertz waveform detection system for generating residual current through air ionization as described in claim 1, characterized in that, The femtosecond laser generating module includes: The laser emitting unit is used to emit high-intensity femtosecond laser pulses; A polarization unit, connected to the laser emitting unit, is used to adjust the polarization direction of the high-intensity femtosecond laser detection pulse.

3. The terahertz waveform detection system for generating residual current through air ionization as described in claim 2, characterized in that, When the polarization unit is used to adjust the polarization direction of the high-intensity femtosecond laser probe pulse, it includes: The polarization unit is used to adjust the polarization direction of the high-intensity femtosecond laser detection pulse. The horizontal polarization is adjusted to the vertical polarization using a half-wave plate, so that the polarization directions of the femtosecond laser detection pulse and the terahertz pulse under test are perpendicular to each other.

4. The terahertz waveform detection system for generating residual current through air ionization as described in claim 1, characterized in that, When the control module is used to change the time delay between the high-intensity femtosecond laser probe pulse and the terahertz pulse to be measured, it includes: The control module is used to acquire the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse, the duration T1 of the strong femtosecond laser detection pulse and the duration T2 of the terahertz test pulse, and to adjust the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse according to the duration T1 of the strong femtosecond laser detection pulse and the duration T2 of the terahertz test pulse.

5. The terahertz waveform detection system for generating residual current through air ionization as described in claim 4, characterized in that, When adjusting the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse based on the duration T1 of the strong femtosecond laser detection pulse and the duration T2 of the terahertz test pulse, the adjustment includes: The control module is also used to preset the adjustment range T of the time delay τ between the terahertz test pulse and the strong femtosecond laser detection pulse, where T = T1 + T2; The control module is also used to continuously increase the time delay τ between the strong femtosecond laser detection pulse and the terahertz test pulse according to a preset adjustment range T; When τ≤T, the current detection module adjusts the time delay τ once every time it completes a measurement of the remaining current under the current time delay. When τ > T, stop adjusting the time delay τ; When the time delay τ is adjusted, the control module is used to enable the terahertz pulse to completely sweep across the strong femtosecond laser detection pulse, thereby adjusting the time delay τ between the strong femtosecond laser detection pulse and the terahertz pulse to be measured.

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