Plug-in terahertz digital holographic device based on waveguide

Abstract

The invention discloses a waveguide-based pluggable terahertz digital holographic device, and belongs to the field of terahertz digital holographic imaging. The device comprises a terahertz radiation source, a terahertz waveguide tube, a terahertz semi-transparent and semi-reflecting mirror, a terahertz focusing lens, a terahertz beam expanding collimator, an imaging sample, a terahertz detector, a metal reflecting mirror and a computer. According to the terahertz digital holographic device, the terahertz waveguide is used for replacing a traditional terahertz digital holographic space light path, discrete devices in the traditional light path are integrated into the waveguide, the terahertz digital holographic device is compact in integration, and the problems that an existing terahertz digital holographic device is complex in structure and large in size are solved; through the design, the terahertz source can be directly aligned with the terahertz waveguide tube for insertion and extraction, and the problem that the existing terahertz digital holographic optical path is time-consuming in installation and adjustment and difficult in alignment due to the fact that terahertz waves are invisible is solved. The digital holographic imaging of the sample is conveniently realized, the quantitative holographic data of the sample including the amplitude and the phase are obtained, and the defect of terahertz wave intensity imaging is overcome, so that the digital holographic imaging method has wide application prospects in the fields of terahertz wave nondestructive testing, biomedical imaging, safety inspection and the like.

Description

Technical Field

[0001] The invention belongs to the field of terahertz digital holography, and in particular relates to a plug-in type terahertz digital holography device based on waveguide. Background Art

[0002] Terahertz (THz) waves refer to waves with a frequency between 0.1 and 10 THz (1 THz = 10 12 Hz) electromagnetic waves, with a corresponding wavelength range of 0.03-3 mm, which is between microwaves and infrared waves in the electromagnetic spectrum.

[0003] Terahertz waves have excellent penetration properties for non-polar materials such as plastics and clothing. At the same time, terahertz waves have low photon energy and will not cause ionization damage to samples. These superior properties make terahertz imaging technology extremely promising in non-destructive testing, security inspection, and biomedical fields.

[0004] Terahertz digital holography technology utilizes the interference of object light and reference light. By recording interference fringes, it can reconstruct the sample and obtain the amplitude and phase information of the sample, which is of great significance in terahertz engineering applications.

[0005] Terahertz waveguides can reduce the absorption loss of water vapor during the transmission of terahertz waves in free space and are conducive to the integrated construction of terahertz systems.

[0006] At present, almost all terahertz digital holographic systems use discrete devices, lack of integrated design, and have defects such as complex structure, large size, and inconvenient to carry. In addition, the optical path needs to be recalibrated after each move, and the invisibility of terahertz waves also makes the installation and adjustment of the optical path system difficult and time-consuming.

[0007] Currently, imaging systems based on terahertz waveguides all require the antenna of the terahertz radiation source to be externally aligned with the core of the terahertz waveguide. During actual installation and adjustment, it is easy to deviate from the optimal injection position, requiring additional calibration work. Summary of the invention

[0008] The present invention aims to solve the problems of complex structure, large volume, time-consuming installation and adjustment in the current terahertz digital holographic technology, and thus specifically proposes a plug-in terahertz digital holographic device and imaging method based on waveguide. The terahertz waveguide replaces the traditional spatial optical path, and the discrete devices in the traditional optical path are integrated in the terahertz waveguide, so that the terahertz digital holographic device is integrated and compact. By designing the core size of the terahertz waveguide to match the size of the gain antenna of the terahertz radiation source, the terahertz radiation source can be directly plugged into the terahertz waveguide without alignment, so as to achieve plug-and-play.

[0009] To solve the above problems, the present invention proposes the following technical solutions:

[0010] A plug-in terahertz digital holographic device based on waveguide includes a terahertz radiation source, a terahertz waveguide tube, a terahertz semi-transparent and semi-reflective mirror, a terahertz focusing lens, a terahertz beam expansion collimator, an imaging sample, a terahertz detector, a metal reflector, and a computer. The terahertz radiation source is used to generate a terahertz signal; the terahertz waveguide is used to transmit the terahertz wave to reduce the absorption of the terahertz signal by water vapor in the air; the terahertz semi-transparent and semi-reflective mirror is placed in the terahertz waveguide at 45 degrees, and can transmit and reflect the terahertz signal; the terahertz focusing lens can realize the function of focusing the incident terahertz wave; the terahertz beam expansion collimator is located at the end of the terahertz waveguide to expand and collimate the terahertz wave; the imaging sample is placed at any position between the collimated terahertz wave and the detector; the terahertz detector is used to detect the interference fringe intensity value when two terahertz waves interfere with each other; the terahertz reflector is placed in the terahertz waveguide at 50 degrees, and can fully reflect the terahertz signal; the computer images the fringe intensity value collected by the terahertz detector through a recovery algorithm, and serves as a host computer to control the three-dimensional electric control translation stage.

[0011] Furthermore, the terahertz radiation source mentioned above is a continuous terahertz wave, and the size of the gain antenna of the terahertz source matches the size of the hollow core of the terahertz waveguide, and can be directly inserted into the terahertz waveguide for coupling.

[0012] Furthermore, the terahertz waveguide tube described above is a hollow terahertz wave antiresonant waveguide or a photonic crystal waveguide, and its length varies according to the application scenario; the air core of the terahertz waveguide tube has a radius that matches the gain horn of the terahertz source, or any other size that is larger than the radius of the gain horn of the terahertz source, and can be varied according to the application scenario.

[0013] Furthermore, the terahertz semi-transparent and semi-reflective mirror described above is placed in the waveguide at 45 degrees and is an intrinsic high-resistance silicon wafer, or is composed of a non-intrinsic high-resistance silicon wafer material; the ratio of the terahertz semi-transparent and semi-reflective mirror to the reflected terahertz signal is 5:5, or any ratio other than 5:5.

[0014] Furthermore, the terahertz wave focusing lens mentioned above is a plano-convex lens or a bi-convex lens, and its focal length and format vary according to actual application scenarios.

[0015] Furthermore, the terahertz beam expander and collimator described above is composed of a negative lens and a positive lens made of the same material as the waveguide tube, and the two are connected and fixed by a ring structure of the same material to achieve beam expansion and collimation. The focal length and format of the two are changed according to the actual application scenario.

[0016] Furthermore, the terahertz wave metal reflector mentioned above is placed in the waveguide at 50°, and is a metal plate, a metal off-axis parabolic mirror, or a plate or off-axis parabolic mirror with a metal layer on the surface, and its materials include but are not limited to quartz glass and HRFZ-Si. The terahertz semi-transparent and semi-reflective mirror, focusing lens, and terahertz reflector mentioned above are directly integrated in the terahertz waveguide.

[0017] Furthermore, the terahertz waveguide, focusing lens and terahertz beam expander collimator mentioned above are prepared by 3D printing, and the materials include but are not limited to TPX, Teflon, PLA, and ABS.

[0018] Furthermore, the terahertz detector mentioned above is a continuous terahertz wave detector, corresponding to the terahertz radiation source used.

[0019] Furthermore, the imaging sample or the rest of the system is fixed on a three-dimensional electrically controlled translation stage, and the sample is scanned and the terahertz digital holographic imaging is recorded through a LabVIEW host computer program written on a computer.

[0020] A method for using a plug-in terahertz digital holographic device based on a waveguide,

[0021] Firstly, the terahertz wave generated by the terahertz radiation source is directly coupled into the terahertz waveguide for low-loss transmission. After passing through the terahertz focusing lens and the terahertz semi-transparent and semi-reflective mirror, the transmitted part of the terahertz signal is continuously transmitted to the terahertz beam expander collimator. Then, the imaging sample is placed on the extension line of the waveguide, that is, on the path of the collimated terahertz wave, which serves as the object light wave. The reflected part of the terahertz signal is transmitted to the metal reflector to change the transmission direction, and is re-coupled to the terahertz waveguide for transmission. After being expanded and collimated by the terahertz beam expander collimator at the end of the waveguide, it is emitted as the reference light.

[0022] Secondly, a terahertz detector is placed at the intersection of the extension lines of the object light wave and the reference light wave. After passing through the sample, the terahertz wave carrying the sample information is transmitted to the terahertz detector along a straight line as the object light wave, and the terahertz wave that has not passed through the sample is also transmitted to the same place as the reference light. The object light and the reference light interfere at this place, and the terahertz detector is used to collect and detect the intensity value of the interference fringes.

[0023] Finally, the LabVIEW host computer program written in the computer is used to control the three-dimensional electric translation stage, read the collected and detected interference fringe intensity values ​​into the computer, and perform imaging through the corresponding recovery algorithm.

[0024] Furthermore, the above-mentioned three-dimensional electric translation stage includes two configurations during confocal imaging:

[0025] 1. The imaging sample remains stationary, and the rest of the body is fixed on a three-dimensional electric translation stage.

[0026] 2. The imaging sample is fixed on a three-dimensional electric translation stage, while the rest of the body remains stationary.

[0027] Advantages and beneficial effects of the present invention:

[0028] The present invention provides a plug-in terahertz digital holographic device based on waveguide, which integrates discrete devices in the traditional optical path into the terahertz waveguide, so that the terahertz digital holographic device is compactly integrated, and the gain antenna of the terahertz radiation source matches the size of the terahertz waveguide tube, and the gain antenna can be directly inserted into the air core of the terahertz waveguide tube, without calibration, plug and play, improving coupling efficiency, and improving system convenience and accuracy. The present invention is to solve the problems of complex structure, large volume, and time-consuming optical path calibration in the current terahertz digital holographic technology. It can more conveniently realize digital holographic imaging of samples and obtain more abundant information inside the imaging samples, and has broad application prospects in the fields of non-destructive testing, biomedicine, security inspection, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 Schematic diagram of a waveguide-based terahertz digital holographic device.

[0031] Figure 2 Schematic diagram of the cross-sectional structure of a terahertz waveguide.

[0032] Figure numerals: 1 - terahertz radiation source; 2 - terahertz waveguide; 3 - terahertz semi-transparent and semi-reflective mirror; 4 - terahertz focusing lens; 5 - terahertz beam expander and collimator; 6 - imaging sample; 7 - terahertz detector; 8 - metal reflector; 9 - computer. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Embodiment 1:

[0035] Figure 1 Schematic diagram of a plug-in terahertz digital holographic device based on waveguide, including a terahertz radiation source 1, a terahertz waveguide tube 2, a terahertz semi-transparent and semi-reflective mirror 3, a terahertz focusing lens 4, an imaging sample 5, a terahertz beam expander collimator 6, a terahertz detector 7, a metal reflector 8, and a computer 9. The terahertz radiation source 1 is used to generate a terahertz signal; the terahertz waveguide tube 2 is used to transmit the terahertz wave to reduce the absorption of the terahertz signal by water vapor in the air; the terahertz semi-transparent and semi-reflective mirror 3 is placed in the terahertz waveguide tube at 45 degrees, and can transmit and reflect the terahertz signal; the terahertz focusing lens 4 can realize the function of focusing the incident terahertz wave; the imaging sample 5 is placed between the terahertz wave collimated and the terahertz detector; the terahertz beam expansion collimator 6 is used to expand and collimate the terahertz wave emitted from the waveguide tube; the terahertz detector 7 is used to detect the intensity of the terahertz signal after being transmitted by the sample; the metal reflector 8 is used to reflect the terahertz wave; the computer 9 is used to write a LabVIEW host computer program to control the three-dimensional electric-controlled translation stage in a linked manner, and image the recorded interference fringes through a recovery algorithm.

[0036] The terahertz radiation source 1 used in the implementation of the present invention is a commercial avalanche diode, which outputs a continuous terahertz wave with a frequency of 0.1 THz, a wavelength of 3 mm, and a power of 95 mW. The spot shape is Gaussian and the polarization state is linear. It is coupled to the terahertz waveguide 2 with a cross-sectional structure as shown in Figure 2, and after being focused by the terahertz plano-convex focusing lens 4, it is then passed through a 45° placed high-resistance silicon material 5:5 terahertz semi-transparent and semi-reflective mirror 3, and the transmitted part of the terahertz wave is transmitted to the terahertz beam expander collimator 6, and after being emitted, it is transmitted through the imaging sample 5, and the terahertz wave carrying the sample information is used as the object light wave; the reflected part is transmitted to the metal reflector 8, and after reflection, it is re-coupled into the terahertz waveguide, and continues to be transmitted to the terahertz beam expander collimator as a reference light wave without sample information. The object light wave and the reference light wave meet at the terahertz detector 7, generating interference fringes, the intensity value of the fringes is recorded by the detector and transmitted to the computer 9, and the three-dimensional electric translation stage is controlled by the LabVIEW host computer program written in the computer, and imaging is performed through the recovery algorithm.

[0037] It should be further explained that the cross-sectional structure diagram of the terahertz waveguide 2 is as follows: Figure 2 As shown, the design of its structure and parameters is related to the wavelength of the terahertz radiation source 1 .

[0038] Description of the present invention:

[0039] 1. All features, methods or steps in the process disclosed in the present invention, except for mutually exclusive features or steps, can be combined in any way.

[0040] 2. Any feature disclosed in the present invention, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. In other words, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0041] 3. For those skilled in the art, according to the concept of the present invention, there will be changes in the specific implementation and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A plug-in terahertz digital holographic device based on waveguide, characterized in that The terahertz digital holographic device comprises: a terahertz radiation source (1), a terahertz waveguide (2), a terahertz semi-transparent and semi-reflective mirror (3), a terahertz focusing lens (4), a terahertz beam expander collimator (5), an imaging sample (6), a terahertz detector (7), a metal reflector (8), and a computer (9); the terahertz radiation source (1) is used to generate a terahertz signal; the terahertz waveguide (2) is used to transmit the terahertz wave to reduce the absorption of the terahertz signal by water vapor in the air; the terahertz semi-transparent and semi-reflective mirror (3) is placed in the terahertz waveguide (2) at an angle of 45 degrees, and can transmit the terahertz signal and also reflect the terahertz signal; The terahertz focusing lens (4) can realize the function of focusing the incident terahertz wave; the imaging sample (6) is placed on the path of the collimated terahertz wave; the terahertz beam expander collimator (5) is used to expand and collimate the terahertz wave in the waveguide; the terahertz detector (7) is used to detect interference fringes formed by the interference of object light and reference light; the metal reflector (8) is used to fully reflect the terahertz wave; the terahertz semi-transparent and semi-reflective mirror (3), the terahertz focusing lens (4) and the metal reflector (8) are directly integrated in the terahertz waveguide tube (2).

2. A waveguide-based plug-in terahertz digital holographic device according to claim 1, characterized in that The terahertz radiation source (1) is a continuous terahertz wave.

3. The waveguide-based plug-in terahertz digital holographic device according to claim 1, characterized in that The terahertz waveguide (2) is a 3D printable hollow terahertz wave anti-resonance waveguide, the length of which varies according to the application scenario.

4. The waveguide-based plug-in terahertz digital holographic device according to claim 1, characterized in that The terahertz semi-transparent and semi-reflective mirror (3) is an intrinsic high-resistance silicon wafer, or is composed of a non-intrinsic high-resistance silicon wafer material; the ratio of the terahertz semi-transparent and semi-reflective mirror (3) for transmitting and reflecting terahertz signals can be 5:5, or any ratio other than 5:5, and the specific ratio depends on actual needs.

5. The waveguide-based plug-in terahertz digital holographic device according to claim 1, characterized in that The terahertz focusing lens (4) is a plano-convex lens or a bi-convex lens, and its focal length and format vary according to actual application scenarios.

6. The waveguide-based plug-in terahertz digital holographic device according to claim 1, characterized in that The terahertz beam expansion and collimator (5) is composed of a negative lens and a positive lens made of the same material as the waveguide tube. The two are connected and fixed by a ring structure made of the same material to achieve beam expansion and collimation. The focal length and format of the two lenses are changed according to the actual application scenario.

7. The waveguide-based plug-in terahertz digital holographic device according to claim 1, characterized in that The metal reflector (8) is a metal flat plate, a metal off-axis parabolic mirror, or a flat plate or an off-axis parabolic mirror with a metal layer coated on the surface.

8. The waveguide-based plug-in terahertz digital holographic device according to claim 1, characterized in that The terahertz waveguide tube (2), the terahertz focusing lens (4) and the terahertz beam expansion collimator (5) are prepared by 3D printing; the materials include but are not limited to TPX, Teflon, PLA, and ABS.

9. The waveguide-based plug-in terahertz digital holographic device according to claim 1, characterized in that The terahertz detector (7) is a continuous terahertz wave detector or a pulsed terahertz wave detector, corresponding to the terahertz radiation source (1) used.

10. The waveguide-based plug-in terahertz digital holographic device according to claim 1, characterized in that The imaging sample (6) or the rest of the system can be fixed on a three-dimensional electric-controlled translation stage, and the three-dimensional electric-controlled translation stage and the terahertz detector can be linked and controlled by a LabVIEW host computer program written by a computer (9) to scan the sample and record the terahertz digital holographic imaging.

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