CN209745811U - Broadband tunable terahertz detection device - Google Patents
Broadband tunable terahertz detection device Download PDFInfo
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- CN209745811U CN209745811U CN201822009347.9U CN201822009347U CN209745811U CN 209745811 U CN209745811 U CN 209745811U CN 201822009347 U CN201822009347 U CN 201822009347U CN 209745811 U CN209745811 U CN 209745811U
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Abstract
the application provides a broadband tunable terahertz detection device. The broadband tunable terahertz detection device at least comprises: a first laser to generate a first output beam; a second laser that generates a second output beam, wherein the wavelength of the first output beam is different from the wavelength of the second output beam; the optical fiber coupler is respectively coupled with the first laser and the second laser and used for generating a third output beam according to the first output beam and the second output beam; the transmitting circuit is coupled with the first output end of the optical fiber coupler and used for generating a terahertz transmitting signal according to the third output light beam and transmitting the terahertz transmitting signal to the surface of the sample; and the receiving circuit is coupled with the second output end of the optical fiber coupler and used for receiving the terahertz emission signal passing through the surface of the sample. The wavelength of the terahertz signal in the broadband tunable terahertz detection device can be tuned, and the spectrum range of the broadband tunable terahertz detection device is widened.
Description
Technical Field
The application relates to the field of related spectrum technologies, in particular to a broadband tunable terahertz detection device.
background
The existing terahertz time-domain spectrograph generally adopts a single laser, and can only generate femtosecond pulses with single frequency to detect a detected sample because the wavelength of a signal output by the laser is fixed. If femtosecond pulses with other frequencies are needed, only the laser can be replaced, and the replacement of the laser is expensive and easily damages the terahertz time-domain spectrometer.
Disclosure of Invention
The application provides a broadband tunable terahertz detection device to solve the problem that a terahertz time-domain spectrometer in the prior art cannot generate terahertz signals of multiple frequencies.
In order to solve the above technical problem, the present application provides a broadband tunable terahertz detection device, which at least includes:
A first laser to generate a first output beam;
A second laser that produces a second output beam, wherein the wavelength of the first output beam is different from the wavelength of the second output beam;
a fiber coupler coupled to the first laser and the second laser, respectively, for generating a third output beam from the first output beam and the second output beam;
The transmitting circuit is coupled with the first output end of the optical fiber coupler and used for generating a terahertz transmitting signal according to the third output light beam and transmitting the terahertz transmitting signal to the surface of a sample;
And the receiving circuit is coupled with the second output end of the optical fiber coupler and used for receiving the terahertz emission signal passing through the surface of the sample.
In this application, the broadband tunable terahertz detection device at least includes: a first laser to generate a first output beam; a second laser that generates a second output beam, wherein the wavelength of the first output beam is different from the wavelength of the second output beam; the optical fiber coupler is respectively coupled with the first laser and the second laser and used for generating a third output beam according to the first output beam and the second output beam; the transmitting circuit is coupled with the first output end of the optical fiber coupler and used for generating a terahertz transmitting signal according to the third output light beam and transmitting the terahertz transmitting signal to the surface of the sample; and the receiving circuit is coupled with the second output end of the optical fiber coupler and used for receiving the terahertz emission signal passing through the surface of the sample. In the broadband tunable terahertz detection device, the frequency of the terahertz signal for detecting the sample to be detected is determined by the frequencies of the signals generated by the first laser and the second laser, so that the frequency of the terahertz signal for detecting the sample to be detected can be widened by increasing the number of the lasers.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts. Wherein:
FIG. 1 is a schematic structural diagram of an embodiment of a terahertz time-domain spectroscopy detection apparatus according to the present application;
FIG. 2 is a schematic structural diagram of another embodiment of the terahertz time-domain spectroscopy detection apparatus of the present application;
FIG. 3 is a schematic structural diagram of an embodiment of a broadband tunable terahertz detection apparatus according to the present application;
Fig. 4 is a schematic structural diagram of an embodiment of the detection apparatus of the present application.
Detailed Description
the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not limiting of the application. It should be further noted that, for the convenience of description, only some of the structures related to the present application are shown in the drawings, not all of the structures. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The terahertz time-domain spectrum detection device is used for generating and detecting a time-resolved terahertz electric field by utilizing femtosecond pulses, and then obtaining spectrum information of a detected sample through algorithms such as Fourier transform and the like. Because the vibration and rotation energy levels of macromolecules forming the sample are mostly in the terahertz wave band, the macromolecules, particularly biological and chemical macromolecules, are a substance group with physical properties, and the terahertz time-domain spectrum detection device can be used for analyzing and identifying the structure, physical properties and the like of a substance through characteristic frequency, so that the properties of the sample can be analyzed.
The application provides a terahertz time-domain spectroscopy detection device, and please refer to fig. 1 specifically, where fig. 1 is a schematic structural diagram of an embodiment of the terahertz time-domain spectroscopy detection device.
the terahertz time-domain spectroscopy detection apparatus 100 includes an excitation source 11, a first fiber coupler 12, at least one second fiber coupler 13, and a transmission circuit 14.
Wherein the excitation source 11 is configured to output an output beam. The excitation source 11 generates the output beam according to different principles according to different constituent types of the excitation source 11, for example, the excitation source 11 of the present embodiment may generate the output beam by one of electrical excitation, optical excitation, and chemical excitation.
The first fiber coupler 12 is coupled to the excitation source 11, and may split or combine the output light beam. In the present embodiment, the first fiber coupler 12 is used to split the output beam output by the excitation source 11 into a first output beam and a second output beam, wherein the first output beam and the second output beam have the same properties.
The second fiber coupler 13 is coupled to an output end of the first fiber coupler 12, and the second fiber coupler 13 is configured to receive the first output beam and split the first output beam into a first emission beam and a second emission beam, wherein the first emission beam and the second emission beam have the same property.
The first and second radiation beams output by the second fiber coupler 13 are respectively coupled into a radiation circuit 14, and the radiation circuit 14 includes a radiation antenna (not shown in the figure). The transmitting circuit 14 respectively performs signal processing on the first transmitting beam and the second transmitting beam to obtain terahertz transmitting signals, and then transmits the processed terahertz transmitting signals to the surface of the sample through the transmitting antennas respectively. Specifically, the transmission circuit 14 transmits a first terahertz transmission signal to the first sample surface, and the transmission circuit 14 transmits a second terahertz transmission signal to the second sample surface.
Corresponding to the transmitting end, the terahertz time-domain spectroscopy apparatus 100 further includes a receiving end.
specifically, the terahertz time-domain spectroscopy detection apparatus 100 further includes at least one third fiber coupler 15 and a receiving circuit 16.
Wherein the third fiber coupler 15 is coupled to another output end of the first fiber coupler 12, and the third fiber coupler 15 is configured to receive the second output light beam and split the second output light beam into a first receiving light beam and a second receiving light beam, wherein the first receiving light beam and the second receiving light beam have the same property.
The first received beam and the second received beam output by the third fiber coupler 15 are respectively coupled into a receiving circuit 16, and the receiving circuit 16 includes a receiving antenna (not shown in the figure). The receiving circuit 16 receives the terahertz transmission signal passing through the sample surface through the receiving antenna, specifically, the receiving circuit 16 receives the first terahertz transmission signal passing through the first sample surface, and the receiving circuit 16 receives the second terahertz transmission signal passing through the second sample surface.
The receiving circuit 16 is triggered by the first terahertz transmission signal to convert the first receiving light beam into a first terahertz receiving signal related to the first sample; the receiving circuit 16 is triggered by the second terahertz transmission signal to convert the second receiving beam into a second terahertz receiving signal with respect to the second sample. The first terahertz receiving signal and the second terahertz receiving signal acquired by the receiving circuit 16 can represent the time-domain spectral characteristics of the first sample and the time-domain spectral characteristics of the second sample respectively.
In this embodiment, the excitation source 11 outputs an output light beam, and the first optical fiber coupler 12 and the second optical fiber coupler 13 can generate a first terahertz transmission signal and a second terahertz transmission signal, and the first optical fiber coupler 12 and the third optical fiber coupler 15 can generate a first terahertz reception signal and a second terahertz reception signal, so as to form two sets of signal sets for detecting a time-domain spectrum of a sample, and the two sets of signal sets do not interfere with each other. Compared with the prior art, the terahertz time-domain spectroscopy detection apparatus 100 of the present embodiment can generate two sets of signal sets that do not interfere with each other simultaneously, and can effectively improve the resource utilization rate.
furthermore, in the present embodiment, only one second fiber coupler 15 and one third fiber coupler 16 are provided, so as to generate two sets of signal sets for detecting the time domain spectrum of the sample; in other embodiments, only the number of the second fiber coupler 15 and/or the third fiber coupler 16 needs to be increased, so that a plurality of signal sets for detecting the time-domain spectrum of the sample can be obtained, thereby improving the scalability of the terahertz time-domain spectrum detection apparatus 100.
Based on the terahertz time-domain spectroscopy detection device 100, the present application also provides another terahertz time-domain spectroscopy detection device, and the terahertz time-domain spectroscopy detection device of this embodiment has the advantages of full optical fiber, independent dual detection modes, low cost, and the like, and please refer to fig. 2 specifically, and fig. 2 is a schematic structural diagram of another embodiment of the terahertz time-domain spectroscopy detection device of this application.
The terahertz time-domain spectroscopy detection apparatus 200 includes an excitation source 21, a first fiber coupler 22, at least one second fiber coupler 23, a transmission circuit 24, at least one third fiber coupler 25, and a reception circuit 26. The connection mode of the above components is the same as that of the components in the above embodiments, and is not described herein again.
In the present embodiment, the excitation source 21 may be a femtosecond laser, or other lasers capable of generating femtosecond pulses. The first fiber coupler 22, the second fiber coupler 23 and/or the third fiber coupler 25 are 3dB couplers.
Wherein, the transmitting circuit 24 further includes a first photoconductive transmitting antenna 241 and a second photoelectric transmitting antenna 242, and the number of photoconductive transmitting antennas of the present embodiment corresponds to the number of beams of the above-mentioned terahertz transmission signal.
The first photoconductive transmitting antenna 241 is coupled to an output end of the second fiber coupler 23, and is configured to receive the first transmitting light beam from the second fiber coupler 23, generate a first terahertz transmitting signal according to the first transmitting light beam, and transmit the first terahertz transmitting signal to the first sample surface.
a second photoconductive transmitting antenna 242 is coupled to the other output of the second fiber coupler 23 for receiving the second terahertz transmission beam from the second fiber coupler 23 and generating a second terahertz transmission signal based on the second transmission beam for transmitting the second terahertz transmission signal to the second sample surface.
The first photoconductive transmitting antenna 241 and/or the second photoconductive transmitting antenna 242 may be a photoconductive antenna with a substrate of indium gallium arsenide (InGaAs) material grown at a low temperature.
Further, the transmitting circuit 24 further includes a bias circuit 243, and the bias circuit 243 is coupled to the first photoconductive transmitting antenna 241 and the second photoconductive transmitting antenna 242, respectively. The bias circuit 243 is configured to generate a bias electric field, and when the forbidden bandwidth of the photoconductive material in the first photoconductive transmitting antenna 241 and the second photoconductive transmitting antenna 242 is smaller than the photon energy of the laser, carriers in the indium gallium arsenide (InGaAs) material are accelerated under the action of the bias electric field, so as to form a first photocurrent and a second photocurrent. The first photo current radiates a first terahertz transmission signal through the first photoconductive transmitting antenna 241, and the second photo current radiates a second terahertz transmission signal through the second photoconductive transmitting antenna 242, wherein the first terahertz transmission signal and the second terahertz transmission signal are continuous terahertz signals.
Further, the first terahertz transmission signal radiated by the first photoconductive transmitting antenna 241 forms an angle smaller than 90 ° with the surface of the first sample, so that the first terahertz transmission signal passes through the first sample in a reflective manner. The second terahertz transmission signal radiated by the second photoconductive transmitting antenna 242 makes an angle equal to 90 ° with the surface of the second sample, so that the second terahertz transmission signal passes through the second sample in a transmissive manner. Thereby, the terahertz time-domain spectroscopy apparatus 200 can obtain transmission information and reflection information about the sample to be measured.
The receiving circuit 26 of the present embodiment further includes a first photoconductive receiving antenna 261 and a second photoelectric receiving antenna 262 corresponding to the above-described transmitting circuit 24, and the number of photoconductive receiving antennas of the present embodiment corresponds to the number of beams of the above-described terahertz receiving signal.
The first photoconductive receiving antenna 261 is coupled to an output terminal of the third fiber coupler 25, and is configured to receive the first receiving light beam, so that the first receiving light beam excites carriers of the first photoconductive receiving antenna 261.
the first photoconductive receiving antenna 261 is further configured to receive a first terahertz transmission signal passing through the first sample surface, the first terahertz transmission signal generates a bias electric field on the first photoconductive receiving antenna 261, and carriers of the first photoconductive receiving antenna 261 are accelerated under the action of the bias electric field to form a third photocurrent.
The second photoconductive receiving antenna 262 is coupled to another output terminal of the third optical fiber coupler 25, and a process of forming the fourth photocurrent by the second photoconductive receiving antenna 262 is the same as that of forming the third photocurrent by the first photoconductive receiving antenna 261, which is not described herein again.
The thz time-domain spectroscopy detection apparatus 200 further includes a phase-locked amplifier circuit 27, where the phase-locked amplifier circuit 27 is respectively coupled to the first photoconductive receiving antenna 261 and the second photoconductive receiving antenna 262, and is configured to perform phase-locked amplification on the third photocurrent and the fourth photocurrent, and display waveforms and spectra related to the first sample and the second sample on a related software interface.
further, the terahertz time-domain spectroscopy detection apparatus 200 may further include a dispersion compensation module 28, a first fiber delay device 291 and a second fiber delay device 292.
The dispersion compensation module 28 is coupled to the excitation source 21 at one end and coupled to the first fiber coupler 22 at the other end. The dispersion compensation module can compensate pulse broadening caused by dispersion in the transmission process of the femtosecond laser in the long-distance polarization maintaining optical fiber, thereby ensuring that the pulse width of the femtosecond laser reaching the photoconductive antenna is less than 100 fs.
the first fiber delay device 291 is coupled to the first fiber coupler 22 at one end and the second fiber coupler 23 at the other end, wherein the first fiber delay device 291 comprises at least a first polarization-preserving single-mode fiber (not shown).
The second fiber delay device 292 is coupled to the first fiber coupler 22 at one end and the third fiber coupler 25 at the other end, wherein the second fiber delay device 292 comprises at least a second polarization maintaining single mode fiber (not shown). Further, the length of the second polarization-maintaining single-mode fiber is smaller than that of the first polarization-maintaining single-mode fiber.
the first optical fiber delay device 291 and the second optical fiber delay device 292 can improve the signal-to-noise ratio of the third terahertz signal, and achieve the scanning effect with wide delay and high precision.
In other embodiments, the thz time-domain spectroscopy apparatus 200 may only access the first fiber delay device 291 or only access the second fiber delay device 292, which is not described herein again.
The application also provides a broadband tunable terahertz detection device which is used for generating and detecting a time-resolved terahertz electric field by utilizing the broadband tunable femtosecond pulse and then obtaining the spectral information of a detected sample through algorithms such as Fourier transform and the like.
Referring to fig. 3, fig. 3 is a schematic structural diagram of an embodiment of the broadband tunable terahertz detection device according to the present application.
The broadband tunable terahertz detection device 300 at least comprises a first laser 31, a second laser 32, a fiber coupler 33, a transmitting circuit 34 and a receiving circuit 35.
The first laser 31 is configured to generate a first output beam with a wavelength λ 1, and the second laser 32 is configured to generate a second output beam with a wavelength λ 2, where the wavelength λ 1 of the first output beam is different from the wavelength λ 2 of the second output beam.
The first laser 31 and/or the second laser 32 may be a distributed feedback semiconductor narrow linewidth laser or other laser.
In the present embodiment, a first laser 31 and a second laser 32 are provided; in other embodiments, the number of lasers can be increased or decreased as desired, and will not be described in detail herein.
The fiber coupler 33 may be a 3dB coupler, and one input of the fiber coupler 33 is coupled to the first laser 31 and the other input is coupled to the second laser 32. The fiber coupler 33 is used to couple the first output beam and the second output beam and produce a third output beam having multiple wavelengths (λ 1, λ 2).
In this embodiment, the optical fiber coupler 33 is a 2X2 optical fiber coupler 33, and the optical fiber coupler 33 may be other multi-output optical fiber couplers, such as a 3X2 optical fiber coupler 33, according to the number of lasers, and will not be described herein again.
The transmitting circuit 34 is coupled to an output end of the optical fiber coupler 33, and the transmitting circuit 34 is capable of receiving the third output light beam and transmitting the third output light beam to the surface of the sample to be measured; a receiving circuit 35 is coupled to the other output of the fiber coupler 33, and the receiving circuit 35 can receive the third output beam passing through the surface of the sample to be measured.
Further, the transmission circuit 34 includes a photoconductive transmission antenna 341 and a bias circuit 342.
Wherein the photoconductive transmitting antenna 341 is coupled to the first output terminal of the optical fiber coupler 33, and the photoconductive transmitting antenna 341 is capable of receiving the third output light beam. The third output beam is coupled onto the photoconductive transmitting antenna 341 and generates a first beat signal having a wavelength ω ═ λ 2- λ 1. The frequency of the first beat frequency signal is 100 GHz-10 THz, namely the frequency of the first beat frequency signal just falls on the terahertz waveband.
The photoconductive transmitting antenna 341 may be a photoconductive antenna in which a low-temperature grown indium gallium arsenide (InGaAs) material is a substrate.
A bias circuit 342 is coupled to the photoconductive transmitting antenna 341, the bias circuit 342 being capable of generating a first bias electric field. When the first beat signal impinges on the semiconductor material of the photoconductive transmitting antenna 341, carriers in the semiconductor material can be excited, wherein the carriers include electron and hole pairs. Under the action of the first bias electric field, the carriers are accelerated and form transient photocurrent, and the photocurrent radiates a terahertz transmission signal on the photoconductive transmitting antenna 341. The photoconductive transmitting antenna 341 further transmits the terahertz transmission signal to the surface of the sample to be measured.
Further, the terahertz transmission signal output by the photoconductive transmitting antenna 341 and the surface of the sample to be measured are less than 90 ° to obtain the reflection time domain spectrum of the sample to be measured.
Alternatively, the terahertz transmission signal output by the photoconductive transmitting antenna 341 and the surface of the measured sample are equal to 90 ° to obtain the transmission time domain spectrum of the measured sample.
Further, the broadband tunable terahertz detection device 300 further includes at least one temperature control device 36, the temperature control device 36 is coupled to the first laser 31 and the second laser 32, and the temperature control device 36 controls the temperature of the first laser 31 and the temperature of the second laser 32, so that the first laser 31 and the second laser 32 output light beams with different wavelengths.
Specifically, the temperature control device 36 controls the temperature of the first laser 31, so that the first laser 31 generates a fourth output beam with a wavelength λ 4, where the wavelength λ 4 of the fourth output beam is different from the wavelength λ 1 of the first output beam; the temperature control device 36 controls the temperature of the second laser 32 such that the second laser 32 generates a fifth output beam having a wavelength λ 5, wherein the wavelength λ 5 of the fifth output beam is different from the wavelength λ 2 of the second output beam.
Therefore, the temperature of the laser is controlled by the temperature control device 36, so that the laser can generate a broadband tunable output beam. After temperature control by the temperature control device 36, the fourth output beam with the wavelength λ 4 and the fifth output beam with the wavelength λ 5 generate beat signals with the wavelength ω ═ λ 5- λ 4 on the photoconductive transmitting antenna 341. Therefore, the frequency of the output beat frequency signal can be tuned through temperature control. Therefore, the broadband tunable terahertz detection device 300 can select a low-cost laser, and the frequency of the beat frequency signal falls on the terahertz waveband through the control of the temperature control device, so that the time-domain spectrum measurement of the detected sample can be completed.
Further, in the present embodiment, the temperature control device 36 controls the temperatures of the first laser 31 and the second laser 32 simultaneously, in other embodiments, the broadband tunable terahertz detecting device 300 may further include a plurality of temperature control devices 36, and each temperature control device 36 controls the temperature of the corresponding laser to increase the tunable frequency band.
the receiving circuit 35 of the present embodiment further includes a photoconductive receiving antenna 351 and a phase-locked amplifying circuit 352 corresponding to the above-described transmitting circuit 34.
The photoconductive receiving antenna 351 and the second output end of the optical fiber coupler 33 are coupled to receive the third output light beam, so that the third output light beam generates a second beat signal, the wavelength of the second beat signal is the same as the wavelength of the first beat signal, and the second beat signal excites a second carrier of the photoconductive receiving antenna 351.
The photoconductive receiving antenna 351 further receives a terahertz transmission signal passing through the surface of the detected sample, the terahertz transmission signal generates a second bias electric field on the photoconductive receiving antenna 351, and the second current carrier is accelerated under the action of the second bias electric field to form a transient second photocurrent.
the phase-locked amplifying circuit 352 is coupled to the photoconductive receiving antenna 351, and the phase-locked amplifying circuit 352 performs a phase-locked amplifying process on the second photoelectric current, and displays a waveform and a frequency spectrum related to the measured sample on a related software interface.
Further, the broadband tunable terahertz detection device 300 can also include a first fiber delay device 371 and a second fiber delay device 372.
The first optical fiber delay device 371 has one end coupled to the optical fiber coupler 33 and the other end coupled to the photoconductive transmitting antenna 341, wherein the first optical fiber delay device 371 comprises at least a first polarization maintaining single mode fiber (not shown).
The second fiber delay device 372 has one end coupled to the fiber coupler 33 and the other end coupled to the photoconductive receiving antenna 351, wherein the second fiber delay device 372 comprises at least a second polarization maintaining single mode fiber (not shown). Further, the length of the second polarization-maintaining single-mode fiber is smaller than that of the first polarization-maintaining single-mode fiber.
The first optical fiber delay device 371 and the second optical fiber delay device 372 can improve the signal-to-noise ratio of the third terahertz signal, and realize the scanning effect with wide delay and high precision.
The application also provides a terahertz detection device, which is used for generating and detecting a time-resolved terahertz electric field by utilizing the broadband tunable femtosecond pulse, and then obtaining the spectral information of a detected sample through algorithms such as Fourier transform and the like.
Referring to fig. 4, fig. 4 is a schematic structural diagram of an embodiment of the detection apparatus of the present application.
The detection apparatus 400 of the present embodiment includes at least a first laser 411, a second laser 412, a first fiber coupler 42, at least one second fiber coupler 43, and a transmission circuit 44.
Wherein the first laser 411 is used to generate a first output beam with a wavelength λ 1, and the second laser 412 is used to generate a second output beam with a wavelength λ 2, wherein the wavelength λ 1 of the first output beam is different from the wavelength λ 2 of the second output beam.
The first laser 411 and/or the second laser 412 may be a distributed feedback semiconductor narrow linewidth laser or other laser.
In the present embodiment, a first laser 411 and a second laser 412 are provided; in other embodiments, the number of lasers can be increased or decreased as desired, and will not be described in detail herein.
The first fiber coupler 42 has one input coupled to the first laser 411 and another input coupled to the second laser 412. The first fiber coupler 42 is used to couple the first output beam and the second output beam and produce a third output beam having multiple wavelengths (λ 1, λ 2).
the second fiber coupler 43 is coupled to an output of the first fiber coupler 42, and the second fiber coupler 43 is configured to receive the third output beam and split the third output beam into a first emission beam and a second emission beam, wherein the first emission beam and the second emission beam have the same property.
The first and second radiation beams output by the second fiber coupler 43 are respectively coupled into a radiation circuit 44, and the radiation circuit 44 includes a radiation antenna (not shown). The transmitting circuit 44 performs signal processing on the first and second transmitted beams respectively to generate a first terahertz transmitting signal and a second terahertz transmitting signal, and then transmits the processed terahertz transmitting signals to the surface of the sample through the transmitting antennas respectively. Specifically, the transmission circuit 44 transmits a first terahertz transmission signal to the first sample surface, and the transmission circuit 44 transmits a second terahertz transmission signal to the second sample surface.
Further, the transmission circuit 44 further includes a first photoconductive transmission antenna 441 and a second photoconductive transmission antenna 442, and the number of photoconductive transmission antennas of the present embodiment corresponds to the number of beams of the above-described terahertz transmission signal.
The first photoconductive transmitting antenna 441 is coupled to an output of the second fiber coupler 43 for receiving a first transmitting beam from the second fiber coupler 43, the first transmitting beam being coupled to the first photoconductive transmitting antenna 441 and generating a first beat signal.
a second photoconductive transmitting antenna 442 is coupled to the other output of the second fiber coupler 43 for receiving the second transmitted light beam from the second fiber coupler 43, which is coupled to the second photoconductive transmitting antenna 442 and generates a second beat signal.
Wherein, the wavelengths of the second beat frequency signals of the first beat frequency signals are all omega-lambda 2-lambda 1.
among them, the first photoconductive transmitting antenna 441 and/or the second photoconductive transmitting antenna 442 may be a photoconductive antenna in which a low-temperature grown indium gallium arsenide (InGaAs) material is a substrate.
Further, the transmitting circuit 44 further includes a bias circuit 443, and the bias circuit 443 is coupled to the first photoconductive transmitting antenna 441 and the second photoconductive transmitting antenna 442, respectively. The bias circuit 443 is used to generate a bias electric field,
When the first beat signal impinges on the semiconductor material of the first photoconductive transmitting antenna 441, causing the forbidden bandwidth of the photoconductive material in the first photoconductive transmitting antenna 441 to be less than the photon energy of the laser, carriers in the semiconductor material are excited, wherein the carriers include electron and hole pairs. Under the action of the bias electric field, the carriers are accelerated and form a transient photocurrent, and the photocurrent radiates a first terahertz transmission signal on the first photoconductive transmitting antenna 441. The first photoconductive transmitting antenna 441 further transmits the first terahertz transmission signal to the first sample surface.
The process of the second photoconductive transmitting antenna 442 generating the second terahertz transmission signal and transmitting the second terahertz transmission signal to the second sample surface is the same as the above process, and is not described in detail herein.
The first terahertz transmission signal and the second terahertz transmission signal are continuous terahertz signals.
Further, the first terahertz transmission signal radiated by the first photoconductive transmitting antenna 441 forms an angle smaller than 90 ° with the surface of the first sample, so that the first terahertz transmission signal passes through the first sample in a reflective manner. The second terahertz transmission signal radiated by the second photoconductive transmitting antenna 442 forms an angle equal to 90 ° with the surface of the second sample, so that the second terahertz transmission signal passes through the second sample in a transmissive manner. Thereby, the terahertz time-domain spectroscopy apparatus 400 can obtain transmission information and reflection information about the sample under test.
Further, the terahertz detection device 400 of the present embodiment further includes at least one temperature control device 45, the temperature control devices 45 are respectively coupled to the first laser 411 and the second laser 412, and the temperature control devices 45 respectively control the temperatures of the first laser 411 and the second laser 412, so that the first laser 411 and the second laser 412 output light beams with different wavelengths.
Specifically, the temperature control device 45 controls the temperature of the first laser 411, so that the first laser 411 generates a fourth output beam with a wavelength λ 4, wherein the wavelength λ 4 of the fourth output beam is different from the wavelength λ 1 of the first output beam; the temperature control device 45 controls the temperature of the second laser 412 such that the second laser 412 generates a fifth output beam having a wavelength λ 5, wherein the wavelength λ 5 of the fifth output beam is different from the wavelength λ 2 of the second output beam.
Therefore, the temperature of the laser is controlled by the temperature control device 45, so that the laser can generate a broadband tunable output beam. After the temperature control of the temperature control device 45, the wavelength of the first beat frequency signal generated by the fourth output light beam with the wavelength λ 4 and the fifth output light beam with the wavelength λ 5 on the first photoconductive transmitting antenna 441 is ω ═ λ 5 — λ 4, so that the frequency of the output beat frequency signal can be tuned through the temperature control. Therefore, the broadband tunable terahertz detection device 400 can select a low-cost laser, and the frequency of the beat signal falls on the terahertz waveband through the control of the temperature control device, so that the time-domain spectrum measurement of the detected sample can be completed.
Further, in this embodiment, the temperature control device 45 controls the temperatures of the first laser 411 and the second laser 412 simultaneously, in other embodiments, the broadband tunable terahertz detecting device 400 may further include a plurality of temperature control devices 45, and each temperature control device 45 controls the temperature of the corresponding laser to increase the tunable frequency band.
Corresponding to the transmitting end, the terahertz detection device further comprises a receiving end.
Specifically, the terahertz detection device 400 of the present embodiment further includes at least one third fiber coupler 46 and a receiving circuit 47.
Wherein the third fiber coupler 46 is coupled to another output end of the first fiber coupler 42, and the third fiber coupler 46 is configured to receive the third output beam and split the third output beam into a first received beam and a second received beam, wherein the first received beam and the second received beam have the same property.
The first and second received beams output from the third fiber coupler 46 are respectively coupled into a receiving circuit 47, and the receiving circuit 47 includes a receiving antenna (not shown). The receiving circuit 47 receives the terahertz transmission signal passing through the sample surface through the receiving antenna, specifically, the receiving circuit 47 receives the first terahertz transmission signal passing through the first sample surface, and the receiving circuit 47 receives the second terahertz transmission signal passing through the second sample surface.
The receiving circuit 47 is triggered by the first terahertz transmission signal to convert the first receiving beam into a first terahertz receiving signal related to the first sample; the receiving circuit 47 is triggered by the second terahertz transmission signal to convert the second receiving beam into a second terahertz receiving signal with respect to the second sample. The first terahertz receiving signal and the second terahertz receiving signal acquired by the receiving circuit 47 can represent the time-domain spectral characteristics of the first sample and the time-domain spectral characteristics of the second sample, respectively.
further, corresponding to the above-mentioned transmitting circuit 44, the receiving circuit 47 of the present embodiment further includes a first photoconductive receiving antenna 471 and a second photoelectric receiving antenna 472, and the number of photoconductive receiving antennas of the present embodiment corresponds to the number of beams of the above-mentioned terahertz receiving signal.
the first photoconductive receiving antenna 471 is coupled to an output end of the third optical fiber coupler 46, and is used for receiving the first receiving light beam, so that the first receiving light beam excites carriers of the first photoconductive receiving antenna 471.
The first photoconductive receiving antenna 471 is further configured to receive a first terahertz transmission signal passing through the first sample surface, the first terahertz transmission signal generates a bias electric field on the first photoconductive receiving antenna 471, and carriers of the first photoconductive receiving antenna 471 are accelerated under the action of the bias electric field to form a third photocurrent.
The second photoconductive receiving antenna 472 is coupled to another output end of the third optical fiber coupler 46, and a process of forming the fourth photocurrent by the second photoconductive receiving antenna 472 is the same as the process of forming the third photocurrent by the first photoconductive receiving antenna 471, which is not described herein again.
The terahertz detecting device 400 further includes a phase-locked amplifying circuit 48, where the phase-locked amplifying circuit 48 is respectively coupled to the first photoconductive receiving antenna 471 and the second photoconductive receiving antenna 472, and is configured to perform phase-locked amplification on the third photocurrent and the fourth photocurrent, and then display waveforms and spectrums of the first sample and the second sample on a related software interface.
Further, the terahertz detecting device 400 may also include a first fiber delay device 491 and a second fiber delay device 492.
The first fiber delay device 491 is coupled to the first fiber coupler 42 at one end and coupled to the second fiber coupler 43 at the other end, wherein the first fiber delay device 491 comprises at least a first polarization-preserving single-mode fiber (not shown).
The second fiber delay device 492 is coupled to the first fiber coupler 42 at one end and the third fiber coupler 46 at the other end, wherein the second fiber delay device 492 comprises at least a second polarization maintaining single mode fiber (not shown). Further, the length of the second polarization-maintaining single-mode fiber is smaller than that of the first polarization-maintaining single-mode fiber.
the first optical fiber delay device 491 and the second optical fiber delay device 492 can improve the signal-to-noise ratio of the third terahertz signal, and realize the scanning effect with wide delay and high precision.
In other embodiments, the terahertz detection device 400 can be accessed only to the first fiber delay device 491 or only to the second fiber delay device 492, which is not described herein again.
The terahertz detection device provided by the embodiment of the present application is described in detail above, and a specific example is applied in the description to explain the principle and the implementation of the present application, and the description of the above embodiment is only used to help understand the method and the core idea of the present application; meanwhile, for a person skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.
Claims (10)
1. A broadband tunable terahertz detection device is characterized by at least comprising:
a first laser to generate a first output beam;
A second laser that produces a second output beam, wherein the wavelength of the first output beam is different from the wavelength of the second output beam;
A fiber coupler coupled to the first laser and the second laser, respectively, for generating a third output beam from the first output beam and the second output beam;
the transmitting circuit is coupled with the first output end of the optical fiber coupler and used for generating a terahertz transmitting signal according to the third output light beam and transmitting the terahertz transmitting signal to the surface of a sample;
And the receiving circuit is coupled with the second output end of the optical fiber coupler and used for receiving the terahertz emission signal passing through the surface of the sample.
2. The broadband tunable terahertz detection device of claim 1, further comprising:
at least one temperature control device coupled to the first laser and the second laser, respectively, for controlling the temperature of the first laser and the second laser, respectively, so that the first laser generates a fourth output beam and the second laser generates a fifth output beam;
wherein a wavelength of the fourth output beam is different from a wavelength of the first output beam and a wavelength of the fourth output beam is different from a wavelength of the second output beam.
3. The broadband tunable terahertz detection device of claim 1, wherein the transmit circuit comprises:
A photoconductive transmitting antenna coupled to the first output of the fiber coupler for receiving the third output beam, causing the third output beam to generate a first beat signal and transmitting the first beat signal to the sample surface.
4. the broadband tunable terahertz detection device of claim 3, wherein the transmit circuit further comprises:
A bias circuit coupled to the photoconductive transmitting antenna for generating a first bias electric field;
the first beat frequency signal excites a first carrier of the photoconductive transmitting antenna, the first carrier is accelerated under the action of the first bias electric field to form a first photocurrent, and the first photocurrent radiates a terahertz transmitting signal;
The photoconductive transmitting antenna further transmits the terahertz transmitting signal to the sample surface.
5. The broadband tunable terahertz detection device of claim 4, wherein the receiving circuit comprises:
a photoconductive receiving antenna coupled to the second output end of the fiber coupler for receiving the third output beam, so that the third output beam generates a second beat signal, and the second beat signal excites a second carrier of the photoconductive receiving antenna;
the photoconductive receiving antenna is further used for receiving a terahertz transmission signal passing through the surface of the sample, the terahertz transmission signal generates a second bias electric field on the photoconductive receiving antenna, and the second current carrier is accelerated in the second bias electric field to form a second photocurrent.
6. The broadband tunable terahertz detection device of claim 5, wherein the receive circuit further comprises:
And the phase-locked amplifying circuit is coupled with the photoconductive receiving antenna and is used for performing phase-locked amplifying processing on the second photoelectric current.
7. The broadband tunable terahertz detection device of claim 5, comprising:
A first optical fiber delay device, one end of which is coupled with the optical fiber coupler and the other end is coupled with the photoconductive transmitting antenna;
The first optical fiber delay device at least comprises a first single-mode polarization-maintaining single-mode optical fiber;
The broadband tunable terahertz detection device further comprises:
A second optical fiber delay device, one end of which is coupled with the optical fiber coupler and the other end is coupled with the photoconductive receiving antenna;
The second optical fiber delay device at least comprises a second single-mode polarization-maintaining optical fiber, and the length of the second single-mode polarization-maintaining optical fiber is smaller than that of the first single-mode polarization-maintaining optical fiber.
8. the broadband tunable terahertz detection device of claim 3, wherein an included angle between the terahertz transmission signal output by the photoconductive transmitting antenna and the surface of the sample is less than 90 °.
9. The broadband tunable terahertz detection device of claim 3, wherein an angle between the terahertz transmission signal output by the photoconductive transmitting antenna and the surface of the sample is equal to 90 °.
10. The broadband tunable terahertz detection device of claim 3,
The optical fiber coupler is a 3dB coupler;
the frequency of the first beat frequency signal is 100 GHz-10 THz.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113092072A (en) * | 2021-03-01 | 2021-07-09 | 中国科学院上海微系统与信息技术研究所 | Single-mode terahertz quantum cascade laser tuning characteristic characterization device |
| CN114235708A (en) * | 2021-12-20 | 2022-03-25 | 天津大学 | Terahertz photoacoustic detection device and method |
| CN114696182A (en) * | 2022-03-31 | 2022-07-01 | 中国电子科技集团公司第四十一研究所 | On-chip integrated wide spectrum frequency domain terahertz system |
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2018
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113092072A (en) * | 2021-03-01 | 2021-07-09 | 中国科学院上海微系统与信息技术研究所 | Single-mode terahertz quantum cascade laser tuning characteristic characterization device |
| CN113092072B (en) * | 2021-03-01 | 2022-06-24 | 中国科学院上海微系统与信息技术研究所 | Single-mode terahertz quantum cascade laser tuning characteristic characterization device |
| CN114235708A (en) * | 2021-12-20 | 2022-03-25 | 天津大学 | Terahertz photoacoustic detection device and method |
| CN114235708B (en) * | 2021-12-20 | 2024-03-29 | 天津大学 | Terahertz photoacoustic detection device and method |
| CN114696182A (en) * | 2022-03-31 | 2022-07-01 | 中国电子科技集团公司第四十一研究所 | On-chip integrated wide spectrum frequency domain terahertz system |
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