Terahertz Introduction

       As researchers deepen their research on terahertz waves, terahertz technology is also constantly advancing in the exploration stage, achieving many results, and also attracting more and more scholars' attention. For researchers who have just entered this field, terahertz waves and related technologies are still relatively unfamiliar. In this article, we will discuss terahertz technology and products.

       Terahertz wave (THz wave) is a special frequency band in the electromagnetic spectrum. It is generally believed that THz wave is an electromagnetic wave with a frequency between 0.1 ~10.0 THz and a wavelength range between 30um~3mm. As shown in Figure 1, THz wave is located between microwaves and infrared light in the electromagnetic spectrum, and has the characteristics of both electronics and infrared photonics, and has the cross-border characteristics of optoelectronic fusion.

Figure 1 Schematic diagram of terahertz frequency band

       Due to the imperfect research theory and the lack of efficient terahertz radiation sources, detectors and functional devices, the terahertz spectrum region is not as in-depth and complete as the microwave and infrared research. With the development and utilization of terahertz spectrum resources, terahertz spectroscopy technology, terahertz imaging technology, and terahertz communication technology have made remarkable achievements in recent years.

       Terahertz spectroscopy technology can provide basic structural information of molecules. Terahertz spectrum contains rich physical and chemical information, and also covers low-energy excitation phenomena of electronic materials, liquid molecular vibration and other excitation phenomena. Figure 2 shows three common terahertz spectroscopy techniques.

(c) THz emission spectroscopy system

       Terahertz imaging uses the high transparency and non-destructiveness of terahertz waves and the fact that most materials have fingerprint spectra in the terahertz band to process and analyze the information of the transmission spectrum or reflection spectrum of the imaging sample to obtain the terahertz image of the sample.

       Terahertz imaging technology includes: terahertz time domain point-by-point scanning imaging, terahertz real-time focal plane imaging, terahertz wave computer-assisted tomography, continuous wave imaging, near-field imaging, etc.

(c) Terahertz continuous wave imaging system

       Terahertz spectroscopy and imaging have broad application prospects in the fields of security, material research, medical imaging, non-destructive testing, etc.

(c) Terahertz nondestructive testing

Product Features

Product Features

3D tomography technology is an important research direction in the field of optics at home and abroad. It has been embedded in the entire process of modern industry and cultural and creative industries. It is an important means to obtain the surface morphological characteristics of objects and the basis for the 3D digitization of real objects. Terahertz 3D tomography technology is a relatively mature 3D object imaging and measurement technology. It is a wide-field imaging technology in the form of terahertz spectrum. After solving and reconstructing with a specific algorithm, it can realize 3D slice imaging of objects and accurately analyze the surface and internal complex structure of samples.

The 780002 terahertz 3D tomography system independently developed by our company is the first time-of-flight (FOT) tomography product to be commercialized in China. It can achieve an imaging speed of up to 60 pixels/second, an imaging depth of more than 9mm, and a vertical resolution of ±2um. At the same time, each pixel of the acquired image contains a complete terahertz waveform, so it has the function of spectral measurement. The spectral width can reach 4THz, truly realizing the integration of image and spectrum.

• All-fiber system, more compact, portable design;

• Spectral resolution as low as 2GHz;

• Supports transmission and reflection spectrum measurement modes, suitable for most sample testing needs;

• Matching a dedicated sample chamber unit to achieve sample measurement in a dry environment and eliminate the interference of water vapor;

• A more user-friendly, intelligent and flexible host computer software system.

       Terahertz communication has high-bandwidth communication, which meets the demand for higher and higher communication rates; small antennas and good directivity; small THz scattering and high cloud penetration; the atmosphere is opaque, and water vapor in the atmosphere has strong absorption of THz waves. Therefore, THz communication is suitable for intersatellite communication, air-to-air communication in the stratosphere, short-range ground wireless LAN, short-range secure atmospheric communication and other fields.

       The development of terahertz spectrum and imaging technology is inseparable from the development of terahertz optical devices. Commonly used terahertz optical devices include off-axis parabolic reflectors, terahertz lenses, hollow reflectors, terahertz beam splitters, terahertz polarizers, etc.

       Detron Laser has launched terahertz optical devices such as off-axis parabolic reflectors, hollow reflectors, and terahertz lenses.

       Off-axis parabolic reflector is the most commonly used terahertz reflector in terahertz spectroscopy technology. Its function is to reflect and focus the parallel terahertz beam, and it can also be used in reverse. Refer to Figure 2(a) The role of the parabolic reflector PM in the optical path.

       Detron Laser has launched 25.4mm and 50.8mm diameter 6061-T6 aluminum alloy substrates with gold, silver and aluminum films and an off-axis angle of 90° for off-axis parabolic reflectors. The gold film can achieve a reflectivity of more than 95% in the terahertz band.

Figure 6 Off-axis parabolic reflector

       The function of the hollow retroreflector (also called hollow corner cone, back reflector) is to make the outgoing light 180° out of the incident light, and it is not affected by whether the incident angle is precisely vertical.

        DeChuang Laser has launched hollow retroreflectors with effective apertures of 25.4mm, 50.8mm, and 63.5mm, which are coated with gold and aluminum films. The hollow retroreflector adopts a hollow weight-reducing design structure, which is made of three petals of mutually perpendicular K9 flat glass glued together, which can effectively reduce the weight, so that it is not demanding on the surrounding application environment in application. In this way, the incident light will be reflected back with higher precision, which can reduce the concern about the incident angle.

       Terahertz lens is mainly used for focusing and collimation in terahertz systems. It is widely used in terahertz spectrometers, terahertz imaging systems and other terahertz research products or related fields. The materials with good transmittance in the terahertz band mainly include polymer materials and high-resistance silicon. Among polymer materials, TPX (poly-4-methylpentene) has the best transmittance performance in the terahertz band.