Waveguide-based plug-in terahertz digital holography device

Abstract

The application discloses a waveguide-based plug-in terahertz digital holography device, and belongs to the field of terahertz digital holography imaging. The device comprises a terahertz radiation source, a terahertz waveguide, a terahertz half-transmission half-reflection mirror, a terahertz focusing lens, a terahertz beam expander, an imaging sample, a terahertz detector, a metal mirror and a computer. The application uses a terahertz waveguide to replace a conventional terahertz digital holography space optical path, and integrates discrete devices in the conventional optical path into the waveguide, so that the terahertz digital holography device is integrated compactly, and the problems of complex structure and large volume of the current terahertz digital holography device are solved. The terahertz source can be directly aligned with the terahertz waveguide for plug-in, so that the alignment difficulty problem caused by the invisible terahertz wave in the current terahertz digital holography optical path assembly and adjustment is solved. The digital holographic imaging of the sample is conveniently realized, the quantitative holographic data of the sample including amplitude and phase are acquired, the shortage of terahertz wave intensity imaging is made up, and therefore the application has wide application prospects in the fields of terahertz wave nondestructive testing, biomedical imaging and safety inspection.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of terahertz digital holography, and particularly relates to a plug-in terahertz digital holography device based on a waveguide. BACKGROUND

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

[0003] Terahertz waves have good transmission characteristics for non-polar materials such as plastics and clothes, and the low photon energy of terahertz waves does not cause ionizing damage to samples, which makes the terahertz imaging technology have great application prospects in non-destructive testing, security checks and biomedical fields.

[0004] Terahertz digital holography technology uses the interference of object light and reference light, and can reconstruct the sample by recording interference fringes to 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 integration of terahertz systems.

[0006] At present, most terahertz digital holography systems use discrete devices, lack integrated design, and have defects such as complex structure, large size, and inconvenience for carrying. And each time after moving, the optical path needs to be recalibrated, and the invisible terahertz waves also make the assembly and adjustment of the optical system difficult and time-consuming.

[0007] At present, the imaging system based on the terahertz waveguide needs to align the antenna of the terahertz radiation source to the core of the terahertz waveguide externally, which is easy to deviate from the optimal injection position in actual assembly and adjustment, and needs additional calibration work. SUMMARY

[0008] The application is to solve the problems of complex structure, large size, time-consuming assembly and adjustment in the current terahertz digital holography technology, and thus a plug-in terahertz digital holography device based on a waveguide and an imaging method are proposed. 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 holography device is integrated and compact. The core size of the terahertz waveguide is designed to match the gain antenna size of the terahertz radiation source, so that the terahertz radiation source can be directly plugged into the terahertz waveguide without alignment, realizing plug and play.

[0009] To solve the above problems, the application provides the following technical scheme:

[0010] A waveguide-based plug-in terahertz digital holographic device, comprising a terahertz radiation source, a terahertz waveguide, a terahertz semi-transparent mirror, a terahertz focusing lens, a terahertz beam expander and collimator, an imaging sample, a terahertz detector, a metal mirror, 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 water vapor in the air to the terahertz signal; the terahertz semi-transparent mirror is placed at 45° in the terahertz waveguide and can transmit and reflect the terahertz signal; the terahertz focusing lens can focus the incident terahertz wave; the terahertz beam expander and 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; the terahertz mirror is placed at 50° in the terahertz waveguide and can fully reflect the terahertz signal; the computer images the fringe intensity value collected by the terahertz detector through a recovery algorithm and controls the three-dimensional electrically controlled translation stage as an upper computer.

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

[0012] Further, the above-mentioned terahertz waveguide is an air-core terahertz wave anti-resonance waveguide or a photonic crystal waveguide, and its length can be changed according to the application scenario; the air core of the terahertz waveguide can match the gain horn of the terahertz source in radius, or have any other size larger than the gain horn radius of the terahertz source, which can be changed according to the application scenario.

[0013] Further, the above-mentioned terahertz semi-transparent mirror is placed at 45° in the waveguide and is made of intrinsic high-resistance silicon or non-intrinsic high-resistance silicon; the transmission and reflection ratio of the terahertz semi-transparent mirror is 5:5 or any other ratio.

[0014] Further, the above-mentioned terahertz focusing lens is a plano-convex lens or a biconvex lens, and its focal length and aperture can be changed according to the actual application scenario.

[0015] Further, the above-mentioned terahertz beam expander and collimator is composed of a negative lens and a positive lens made of the same material as the waveguide, and 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 aperture of the two can be changed according to the actual application scenario.

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

[0017] Further, the above-mentioned terahertz waveguide, focusing lens, and terahertz beam expander collimator are prepared by 3D printing, and the material includes but is not limited to TPX, Teflon, PLA, and ABS.

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

[0019] Further, 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 image is recorded through the LabVIEW upper computer program written by the computer.

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

[0021] First, the terahertz wave generated by the terahertz radiation source is directly coupled into the terahertz waveguide for low-loss transmission, and the transmitted part of the terahertz signal continues to be transmitted to the terahertz beam expander collimator through the terahertz focusing lens and the terahertz semi-transparent mirror, then the imaging sample is placed on the extension line of the waveguide, i.e. on the path of the collimated outgoing terahertz wave, which serves as the object light wave; the reflected part of the terahertz signal is transmitted to the metal mirror to change the transmission direction and is recoupled into the terahertz waveguide for transmission, and the terahertz beam expander collimator at the end of the waveguide is expanded and collimated to be emitted as reference light.

[0022] Secondly, a terahertz detector is placed at the intersection of the respective extension lines of the object light wave and the reference light wave. After being transmitted through the sample, the terahertz wave carrying sample information serves as the object light wave and is transmitted along a straight line to the terahertz detector, and the terahertz wave that does not pass through the sample serves as the reference light and is also transmitted to the terahertz detector, where the object light and the reference light interfere, and the interference fringe intensity value is collected and detected by the terahertz detector.

[0023] Finally, through the LabVIEW upper computer program written by the computer, the three-dimensional electrically controlled translation stage is linked and controlled, the collected and detected interference fringe intensity value is read into the computer, and imaging is performed through the corresponding recovery algorithm.

[0024] Further, the above-mentioned three-dimensional electrically controlled translation stage includes two configurations in the confocal imaging process:

[0025] 1. The imaging sample is kept stationary and the rest of the sample is fixed as a whole on a three-dimensional electrically controlled translation stage.

[0026] 2. The imaging sample is fixed on a three-dimensional electrically controlled translation stage, while the rest of the sample is kept stationary.

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

[0028] The present application provides a waveguide-based plug-in terahertz digital holographic device, which integrates discrete devices in the traditional optical path into a terahertz waveguide, making the terahertz digital holographic device compact and integrated, and the gain antenna of the terahertz radiation source matching the size of the terahertz waveguide tube. 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 system convenience and accuracy. The present application 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 the sample and obtain more abundant information inside the imaging sample, and has wide application prospects in the fields of nondestructive testing, biomedicine and security inspection. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

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

[0031] Figure 2 It is a schematic diagram of the cross-sectional structure of a terahertz waveguide tube.

[0032] Reference numerals: 1-terahertz radiation source; 2-terahertz waveguide tube; 3-terahertz half-transmission half-reflection mirror; 4-terahertz focusing lens; 5-terahertz beam expander collimator; 6-imaging sample; 7-terahertz detector; 8-metal mirror; 9-computer. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0034] Embodiment 1:

[0035] Figure 1 The waveguide-based plug-in terahertz digital holographic device schematic diagram comprises a terahertz radiation source 1, a terahertz waveguide tube 2, a terahertz semi-transparent mirror 3, a terahertz focusing lens 4, an imaging sample 5, a terahertz beam expander collimator 6, a terahertz detector 7, a metal mirror 8 and a computer 9. The terahertz radiation source 1 is used for generating a terahertz signal; the terahertz waveguide tube 2 is used for transmitting the terahertz wave to reduce the absorption of water vapor in the air to the terahertz signal; the terahertz semi-transparent mirror 3 is placed at 45° in the terahertz waveguide tube 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 collimation and the terahertz detector; the terahertz beam expander collimator 6 is used for expanding and collimating the terahertz wave emitted by the waveguide tube; the terahertz detector 7 is used for detecting the terahertz signal intensity transmitted through the sample; the metal mirror 8 is used for reflecting the terahertz wave; and the computer 9 is used for writing the LabVIEW host computer program, linkage control of the three-dimensional electrically controlled translation stage and imaging of the recorded interference fringes through the recovery algorithm.

[0036] In the embodiment of the present application, the terahertz radiation source 1 is a commercial avalanche diode, the output frequency is 0.1 THz, the wavelength is 3 mm, the power is 95 mW of continuous terahertz wave, the spot form is Gaussian type, and the polarization state is linear. The terahertz wave is coupled into the terahertz waveguide tube 2 with the cross-section structure as shown in FIG. 2, focused through the terahertz plano-convex focusing lens 4, and then transmitted through the 45°-placed high-resistance silicon material 5:5 terahertz semi-transparent mirror 3. The transmission part of the terahertz wave is transmitted to the terahertz beam expander collimator 6, transmitted through the imaging sample 5 after emission, the terahertz wave carrying the sample information is used as the object light wave; the reflection part is transmitted to the metal mirror 8, re-coupled into the terahertz waveguide tube after reflection, and continuously transmitted to the terahertz beam expander collimator as the reference light wave without sample information. The object light wave and the reference light wave meet at the terahertz detector 7 to generate interference fringes, the intensity value of the fringes is recorded by the detector and transmitted to the computer 9, the LabVIEW host computer program written by the computer is used for linkage control of the three-dimensional electrically controlled translation stage, and imaging is performed through the recovery algorithm.

[0037] It should be further explained that the cross-section structure of the terahertz waveguide tube 2 is shown in FIG. 2, and the structure and parameter design are related to the wavelength of the terahertz radiation source 1. Figure 2

[0038] Related description of the present application:

[0039] ​1. All of the features, methods or steps disclosed in the present application may be combined in any way, except where features or steps are mutually exclusive.

[0040] 2. Any of the features disclosed in the present application may be substituted by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated, each feature is one example only of a number of equivalent or similar features.

[0041] 3. Changes in detail and application of the ideas herein disclosed may be made by those skilled in the art, without departing from the spirit of the application. The scope of the application is therefore to be limited only by the claims.

Claims

1. A waveguide-based pluggable terahertz digital holographic device, characterized in that... The terahertz digital holographic device includes: a terahertz radiation source (1), a terahertz waveguide (2), a terahertz semi-transparent mirror (3), a terahertz focusing lens (4), a terahertz beam expander collimator (5), an imaging sample (6), a terahertz detector (7), a metal mirror (8), and a computer (9); the terahertz radiation source (1) is used to generate terahertz signals; the terahertz waveguide (2) is used to transmit terahertz waves to reduce the absorption of terahertz signals by water vapor in the air; the terahertz semi-transparent mirror (3) is placed at 45° in the terahertz waveguide (2) and can transmit and reflect terahertz signals. The terahertz focusing lens (4) can focus the incident terahertz wave; the imaging sample (6) is placed on the path after the terahertz wave is collimated; 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 the interference fringes formed by the interference of the object light and the reference light; the metal mirror (8) is used for total reflection of the terahertz wave; the terahertz semi-transparent mirror (3), the terahertz focusing lens (4) and the metal mirror (8) are directly integrated into the terahertz waveguide (2).

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

4. A waveguide-based pluggable terahertz digital holographic device according to claim 1, characterized in that... The terahertz semi-transparent and semi-reflective mirror (3) is an intrinsic high-resistivity silicon wafer or is composed of non-intrinsic high-resistivity silicon wafer material.

5. A waveguide-based pluggable terahertz digital holographic device according to claim 1, characterized in that... The terahertz focusing lens (4) is a plano-convex lens or a biconvex lens, and its focal length and field of view are changed according to the actual application scenario.

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

7. A waveguide-based pluggable terahertz digital holographic device according to claim 1, characterized in that... The metal reflector (8) is a metal plate, a metal off-axis parabolic mirror, or a plate or off-axis parabolic mirror with a metal coating on its surface.

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

9. A waveguide-based pluggable 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. A waveguide-based pluggable 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 electrically controlled translation stage. The three-dimensional electrically controlled translation stage and the terahertz detector can be linked and controlled by the LabVIEW host computer program written by the computer (9) to scan the sample and record the terahertz digital holographic imaging.

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