Parameter measuring device and method for terahertz wave beam

Abstract

The invention provides a parameter measurement device and method for a terahertz wave beam, and the device comprises a laser signal generation module which is used for generating a combined laser signal; the to-be-tested terahertz continuous wave radiator outputs a terahertz continuous wave signal based on the combined laser signal; the scanning modulation module is used for carrying out beam scanning and modulation on the terahertz continuous wave signal based on the combined laser signal to generate a reflected laser signal; the optical circulator is used for outputting the combined laser signal to the scanning modulation module and outputting the reflected laser signal to the current signal generation module; the current signal generation module generates a current signal based on the reflected laser signal; and a control and data processing module. The parameter measuring device of the terahertz wave beam is based on all-fiber detection, does not need a spatial light path system which is large in size and difficult to adjust, is high in integration level and simple to operate, can realize non-intrusive terahertz wave beam near-field measurement, and can realize ultra-wideband terahertz wave beam measurement.

Description

Technical Field

[0001] This invention relates to the field of radio metrology and testing, and in particular to a parameter measurement device and method for a terahertz beam. Background Technology

[0002] Terahertz spectroscopy, with its unique properties in the terahertz frequency band, has been widely applied in fields such as industrial non-destructive testing, chemical analysis, security inspection, and space physics. However, as the terahertz frequency increases, waveguide-based terahertz wave transmission methods are gradually becoming insufficient for terahertz applications. For terahertz waves in the form of space radiation, current detection methods include space electro-optic sampling point-by-point scanning and terahertz camera imaging. In the space electro-optic sampling point-by-point scanning method, electro-optic crystals, quarter-wave plates, Wollaston beam splitters, focusing lenses, and balanced photodetectors are typically used as the detection end. The overall detection part consists of a spatial optical path, resulting in poor integration and difficulty in adjustment. In the terahertz camera imaging method, due to the low sensitivity of the terahertz camera, the terahertz beam needs to be focused, making it impossible to directly reflect the original state of the terahertz beam. Furthermore, terahertz camera imaging is an invasive measurement; the metal structure of the terahertz camera introduces disturbances into the terahertz beam, affecting the measurement results.

[0003] Therefore, there is an urgent need for a new parameter measurement device for terahertz beams that can overcome the above-mentioned shortcomings. Summary of the Invention

[0004] This invention provides a parameter measurement device for a terahertz beam, comprising:

[0005] Laser signal generation module, used to generate combined laser signals;

[0006] The terahertz continuous wave radiator under test outputs a terahertz continuous wave signal based on the combined laser signal.

[0007] The scanning modulation module performs beam scanning and modulation on the terahertz continuous wave signal based on the combined laser signal to generate the reflected laser signal;

[0008] An optical circulator is connected to the laser signal generation module and the scanning modulation module, respectively, and is used to output the combined laser signal to the scanning modulation module and the reflected laser signal to the current signal generation module.

[0009] A current signal generation module, connected to an optical circulator, generates a current signal based on the reflected laser signal;

[0010] The control and data processing module is connected to the laser signal generation module, the terahertz continuous wave radiator under test, the scanning modulation module, and the current signal generation module, respectively. It is used to control the laser signal generation module to achieve laser tuning, to control the terahertz continuous wave radiator under test to achieve clock synchronization, to control the scanning modulation module to achieve motion control, and to control the current signal generation module to achieve visualization processing of current signals.

[0011] Furthermore, the laser signal generation module includes:

[0012] Two tunable lasers are used to generate two continuous laser beams with adjustable frequencies.

[0013] A 2×2 optical coupler is connected to two tunable lasers respectively to combine two frequency-tunable continuous laser beams into a combined laser signal and output the combined laser signal to an optical circulator.

[0014] Furthermore, the terahertz continuous wave radiator to be measured includes:

[0015] The function generator, connected to the control and data processing module, is used to generate modulated signals;

[0016] The photoconductive antenna, connected to the function generator, outputs a terahertz continuous wave signal based on the combined laser signal and the modulation signal through optical beat frequency method.

[0017] Furthermore, the scanning modulation module includes:

[0018] A miniature electro-optic dielectric probe generates a reflected laser signal by modulating a terahertz continuous wave signal with a combined laser signal.

[0019] The mechanical scanning module is used to hold the miniature electro-optic dielectric probe and carry it to complete beam scanning. The motion control of the mechanical scanning module is realized through the control and data processing module.

[0020] Furthermore, the miniature electro-optic dielectric probe includes:

[0021] Medium sleeve;

[0022] Polarization-maintaining fiber optic pigtails are used to transmit combined laser signals.

[0023] Glass ferrules are placed at the end of polarization-maintaining fiber pigtails to secure them.

[0024] A self-focusing lens is used to focus the combined laser signal onto the first surface of the electro-optic crystal near the polarization-maintaining fiber pigtail.

[0025] Electro-optic crystals generate reflected laser signals by modulating terahertz continuous wave signals with focused combined laser signals.

[0026] Furthermore, the first surface is coated with an anti-reflective coating.

[0027] Furthermore, a reflective coating is applied to the second surface of the electro-optic crystal away from the polarization-maintaining fiber pigtail.

[0028] Furthermore, a terahertz absorbing coating is applied to the inner surface of the dielectric sleeve at the corresponding position of the electro-optic crystal.

[0029] Furthermore, the current signal generation module includes:

[0030] An optical filter is used to extract the upper sideband, which corresponds to the modulation sideband and tunable laser signal of the upconverted terahertz wave continuous signal, from the reflected laser signal. The tunable laser signal corresponds to the higher frequency of the two tunable continuous laser beams.

[0031] A photodetector is used to convert tunable laser signals into electrical signals;

[0032] A current amplifier is used to amplify current signals.

[0033] This invention also provides a method for measuring the parameters of a terahertz beam, comprising the following steps:

[0034] Generate combined laser signals;

[0035] Based on the combined laser signal, a terahertz continuous wave signal is output;

[0036] Based on the combined laser signal, the terahertz continuous wave signal is beam scanned and modulated to generate the reflected laser signal;

[0037] Outputs combined laser signal and reflected laser signal;

[0038] A current signal is generated based on the reflected laser signal.

[0039] This invention provides a terahertz beam parameter measurement device. A laser signal generation module generates a combined laser signal. A terahertz continuous wave radiator under test outputs a terahertz continuous wave signal based on the combined laser signal. A scanning modulation module scans and modulates the terahertz continuous wave signal to generate a reflected laser signal. An optical circulator outputs the combined laser signal to the scanning modulation module and the reflected laser signal to a current signal generation module. The current signal generation module generates a current signal based on the reflected laser signal. This terahertz beam parameter measurement device is based on all-fiber detection, eliminating the need for a bulky and difficult-to-adjust spatial optical path system. It features high integration, simple operation, and non-invasive near-field measurement of terahertz beams. Furthermore, by outputting the terahertz continuous wave signal via optical beat frequency, ultra-wideband terahertz beam measurement can be achieved.

[0040] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and accompanying drawings. Attached Figure Description

[0041] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0042] Figure 1 This is a schematic diagram of the structure of a terahertz beam parameter measurement device according to an embodiment of the present invention;

[0043] Figure 2 This is a schematic diagram of the structure of a miniaturized electro-optic dielectric probe in a terahertz beam parameter measurement device according to an embodiment of the present invention.

[0044] Figure 3 This is a schematic diagram of the measurement results of the radiation pattern of the terahertz continuous wave radiator under test according to an embodiment of the present invention;

[0045] Figure 4 This is a flowchart of a parameter measurement method for a terahertz beam according to an embodiment of the present invention. Detailed Implementation

[0046] To address the technical issues of poor integration and high adjustment difficulty in spatial electro-optic sampling point-by-point scanning methods, and the inability of terahertz camera imaging methods to intuitively reflect the original state of the terahertz beam, which introduces disturbances that affect the measurement results, a parameter measurement device for terahertz beams is provided.

[0047] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. Furthermore, the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0048] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of the embodiments of the present invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein.

[0049] Figure 1 This is a schematic diagram of the structure of a terahertz beam parameter measurement device according to an embodiment of the present invention. See also... Figure 1The parameter measurement device for the terahertz beam includes:

[0050] Laser signal generation module 1 is used to generate combined laser signals;

[0051] The terahertz continuous wave radiator under test 2 outputs a terahertz continuous wave signal based on the combined laser signal;

[0052] Scanning modulation module 3 performs beam scanning and modulation on the terahertz continuous wave signal based on the combined laser signal to generate a reflected laser signal;

[0053] The optical circulator 4 is connected to the laser signal generation module 1 and the scanning modulation module 3 respectively, and is used to output the combined laser signal to the scanning modulation module 3 and the reflected laser signal to the current signal generation module 5.

[0054] The current signal generation module 5 is connected to the optical circulator 4 and generates a current signal based on the reflected laser signal.

[0055] The control and data processing module 6 is connected to the laser signal generation module 1, the terahertz continuous wave radiator under test 2, the scanning modulation module 3, and the current signal generation module 5, respectively. It is used to control the laser signal generation module 1 to achieve laser tuning, to control the terahertz continuous wave radiator under test 2 to achieve clock synchronization, to control the scanning modulation module 3 to achieve motion control, and to control the current signal generation module 5 to achieve visualization processing of current signals.

[0056] Specifically, the laser signal generation module 1 includes:

[0057] Two tunable lasers 11 are used to generate two continuous laser beams with adjustable frequencies. After mixing the two continuous laser beams with adjustable frequencies, a local oscillator signal close to the frequency of the terahertz wave to be measured can be obtained.

[0058] In this embodiment, the wavelength tuning range of the two tunable lasers 11 is 1550nm to 1555nm, the minimum tuning accuracy is 10MHz, and the two output frequency-tunable continuous lasers are both polarization-maintaining lasers. The wavelength adjustment of the two tunable lasers 11 is realized by the control and data processing module 6. The frequencies of the two frequency-tunable continuous lasers are determined by a wavelength meter to be the first frequency f1 and the second frequency f2 (f1>f2). The frequency difference f1-f2 between the first frequency f1 and the second frequency f2 is made to be the same as the frequency of the terahertz continuous wave signal by the control and data processing module 6.

[0059] A 2×2 optical coupler 12 is connected to two tunable lasers 11 respectively, and is used to combine two frequency-tunable continuous laser beams into a combined laser signal, and output the combined laser signal to the optical circulator 4. The combined laser signal contains lasers of two frequencies (f1, f2).

[0060] In this embodiment, the 2×2 optical coupler 12 is a 2×2 polarization-maintaining fiber coupler with a center wavelength of 1550nm, a splitting ratio of 50:50, and a polarization extinction ratio of approximately 20dB.

[0061] Specifically, the terahertz continuous wave radiator 2 to be tested includes:

[0062] Function generator 21 is connected to control and data processing module 6 and is used to generate a modulation signal with a frequency of ft. Control and data processing module 6 controls function generator 21 to ensure clock synchronization of function generator 21.

[0063] The photoconductive antenna 22 is connected to the function generator 21. Based on the combined laser signal and the modulation signal, it outputs a terahertz continuous wave signal through optical beat frequency method. The frequency of the terahertz continuous wave signal is 1 / (f1-f2-ft).

[0064] In this embodiment, the frequency of the terahertz continuous wave signal is 500 GHz.

[0065] Specifically, the scanning modulation module 3 includes:

[0066] The miniature electro-optic dielectric probe 31 modulates a terahertz continuous wave signal based on a combined laser signal to generate a reflected laser signal.

[0067] The mechanical scanning module 32 is used to hold the miniature electro-optic dielectric probe 31 and carry it to complete beam scanning. The motion control of the mechanical scanning module 32 is realized through the control and data processing module 6.

[0068] In this embodiment, the mechanical scanning module 32 is a three-axis mechanical displacement platform.

[0069] Furthermore, Figure 2 This is a schematic diagram of the miniaturized electro-optic dielectric probe in a terahertz beam parameter measurement device according to an embodiment of the present invention. See also... Figure 2 The miniature electro-optic dielectric probe 31 includes:

[0070] Medium sleeve 311;

[0071] Polarization-maintaining fiber pigtail 312 is used to transmit combined laser signals;

[0072] Glass ferrule 313 is disposed at the end of polarization-maintaining fiber pigtail 312 and is used to fix polarization-maintaining fiber pigtail 312.

[0073] Self-focusing lens 314 is used to focus the combined laser signal onto the first surface of electro-optic crystal 315 near polarization-maintaining fiber pigtail 312.

[0074] The electro-optic crystal 315 modulates a terahertz continuous wave signal based on a focused combined laser signal to generate a reflected laser signal.

[0075] Furthermore, the first surface is coated with an anti-reflective coating 316 to reduce the loss of the combined laser signal.

[0076] Furthermore, the second surface of the electro-optic crystal 315, away from the polarization-maintaining fiber pigtail 312, is coated with a reflective coating 317 to reflect the laser signal that has passed through the electro-optic crystal and interacted with the terahertz continuous wave signal back to the optical circulator, forming a reflected laser signal.

[0077] Furthermore, a terahertz absorbing coating 318 is coated on the inner surface of the dielectric sleeve 311 at the corresponding position of the electro-optic crystal 315 to absorb terahertz continuous wave signals outside the effective range of the electro-optic crystal 315, thereby reducing the influence of the miniaturized electro-optic dielectric probe 311 on the electric field. In this embodiment, the terahertz absorbing coating 318 is made of Mxene terahertz absorbing material.

[0078] Specifically, the optical circulator 4 includes three interfaces: the first interface is connected to the 2×2 optical coupler 12, the second interface is connected to the miniaturized electro-optic medium probe 31, and the third interface is connected to the current signal generation module 5.

[0079] Specifically, the current signal generation module 5 includes:

[0080] Optical filter 51 is used to extract the upper sideband, i.e. the modulation sideband corresponding to the upconverted terahertz wave continuous signal, and the tunable laser signal from the reflected laser signal. The tunable laser signal corresponds to the higher frequency (f1) of the two frequency-tunable continuous laser beams.

[0081] In this embodiment, the center frequency of the optical filter is 500 GHz.

[0082] Photodetector 52 is used to convert tunable laser signals into current signals.

[0083] In this embodiment, the photodetector 52 is a 1550nm photodetector on an InGaAs substrate.

[0084] The current amplifier 53 is used to amplify the current signal output by the photodetector.

[0085] In this embodiment, the current amplifier 53 can suppress various noises, and the current amplification gain is 10. 5 .

[0086] Specifically, the control and data processing module 6 uses LabVIEW to develop step tuning software and current data acquisition software.

[0087] Figure 3This is a schematic diagram of the measurement results of the radiation pattern of the terahertz continuous wave radiator under test according to an embodiment of the present invention. See also Figure 3 The measurement results show that the terahertz beam parameter measurement device provided in this embodiment has high measurement sensitivity and the measurement results are relatively accurate.

[0088] In summary, the terahertz beam parameter measurement device provided in this embodiment of the invention generates a combined laser signal through a laser signal generation module 1, outputs a terahertz continuous wave signal based on the combined laser signal through a terahertz continuous wave radiator 2 under test, performs beam scanning and modulation on the terahertz continuous wave signal through a scanning modulation module 3 to generate a reflected laser signal, outputs the combined laser signal to the scanning modulation module through an optical circulator 4, and outputs the reflected laser signal to a current signal generation module 5, which generates a current signal based on the reflected laser signal. This terahertz beam parameter measurement device is based on all-fiber detection, eliminating the need for a bulky and difficult-to-adjust spatial optical path system. It features high integration, simple operation, and enables non-invasive near-field measurement of terahertz beams. Furthermore, by outputting the terahertz continuous wave signal via optical beat frequency, it can achieve ultra-wideband terahertz beam measurement.

[0089] Figure 4 A flowchart illustrating a parameter measurement method for a terahertz beam according to an embodiment of the present invention is shown. See also... Figure 4 The parameter measurement method for the terahertz beam includes the following steps:

[0090] Generate combined laser signals;

[0091] Based on the combined laser signal, a terahertz continuous wave signal is output;

[0092] Based on the combined laser signal, the terahertz continuous wave signal is beam scanned and modulated to generate the reflected laser signal;

[0093] Outputs combined laser signal and reflected laser signal;

[0094] A current signal is generated based on the reflected laser signal.

[0095] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0096] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A parameter measurement device for a terahertz beam, characterized in that, include: Laser signal generation module (1) is used to generate combined laser signals; The terahertz continuous wave radiator under test (2) outputs a terahertz continuous wave signal based on the combined laser signal; The scanning modulation module (3) performs beam scanning and modulation on the terahertz continuous wave signal based on the combined laser signal to generate a reflected laser signal; The optical circulator (4) is connected to the laser signal generation module (1) and the scanning modulation module (3) respectively, and is used to output the combined laser signal to the scanning modulation module (3) and output the reflected laser signal to the current signal generation module (5); The current signal generation module (5) is connected to the optical circulator (4) and generates a current signal based on the reflected laser signal; The control and data processing module (6) is connected to the laser signal generation module (1), the terahertz continuous wave radiator under test (2), the scanning modulation module (3), and the current signal generation module (5), respectively. It is used to control the laser signal generation module (1) to achieve laser tuning, to control the terahertz continuous wave radiator under test (2) to achieve clock synchronization, to control the scanning modulation module (3) to achieve motion control, and to control the current signal generation module (5) to achieve visualization processing of current signals.

2. The parameter measurement device for a terahertz beam according to claim 1, characterized in that, The laser signal generation module (1) includes: Two tunable lasers (11) are used to generate two continuous laser beams with adjustable frequencies. A 2×2 optical coupler (12) is connected to two tunable lasers (11) respectively, for combining two frequency-tunable continuous laser beams into a combined laser signal, and outputting the combined laser signal to an optical circulator (4).

3. The parameter measurement device for a terahertz beam according to claim 1, characterized in that, The terahertz continuous wave radiator (2) to be tested includes: The function generator (21) is connected to the control and data processing module (6) and is used to generate the modulation signal; The photoconductive antenna (22) is connected to the function generator (21) and outputs a terahertz continuous wave signal based on the combined laser signal and the modulation signal through optical beat frequency method.

4. The parameter measurement device for a terahertz beam according to claim 1, characterized in that, The scanning modulation module (3) includes: A miniature electro-optic dielectric probe (31) modulates the terahertz continuous wave signal based on the combined laser signal to generate a reflected laser signal; The mechanical scanning module (32) is used to hold the miniature electro-optic dielectric probe (31) and carry it to complete beam scanning. The motion control of the mechanical scanning module (32) is realized through the control and data processing module (6).

5. The parameter measurement device for a terahertz beam according to claim 4, characterized in that, The miniature electro-optic dielectric probe (31) includes: Medium sleeve (311); A polarization-maintaining fiber pigtail (312) is used to transmit the combined laser signal; A glass ferrule (313) is disposed at the end of the polarization-maintaining fiber pigtail (312) for fixing the polarization-maintaining fiber pigtail (312); A self-focusing lens (314) is used to focus the combined laser signal onto the first surface of the electro-optic crystal (315) near the polarization-maintaining fiber pigtail (312); The electro-optic crystal (315) modulates the terahertz continuous wave signal based on the focused combined laser signal to generate the reflected laser signal.

6. The parameter measurement device for a terahertz beam according to claim 5, characterized in that, The first surface is coated with an anti-reflective coating (316).

7. The parameter measurement device for a terahertz beam according to claim 5, characterized in that, The second surface of the electro-optic crystal (315) away from the polarization-maintaining fiber pigtail (312) is coated with a reflective coating (317).

8. The parameter measurement device for a terahertz beam according to claim 5, characterized in that, The inner surface of the dielectric sleeve (311) is coated with a terahertz absorbing coating (318) at the corresponding position of the electro-optic crystal (315).

9. The parameter measurement device for a terahertz beam according to claim 2, characterized in that, The current signal generation module (5) includes: An optical filter (51) is used to extract the upper sideband, i.e. the modulation sideband corresponding to the upconverted terahertz wave continuous signal, and the tunable laser signal from the reflected laser signal. The tunable laser signal corresponds to the higher frequency of the two frequency-tunable continuous laser beams. A photodetector (52) is used to convert the tunable laser signal into a current signal; A current amplifier (53) is used to amplify the current signal.

10. The method for measuring the parameters of a terahertz beam according to claim 1, characterized in that, Includes the following steps: Generate combined laser signals; Based on the combined laser signal, a terahertz continuous wave signal is output; Based on the combined laser signal, the terahertz continuous wave signal is beam-scanned and modulated to generate a reflected laser signal; Output the combined laser signal and the reflected laser signal; A current signal is generated based on the reflected laser signal.

Images