In this talk, I will introduce several of our work on tunable and reconfigurable THz devices using plasmonics and metamaterials, including high efficiency continuous wave THz emitter, tunable THz response using InSb plasmons, graphene multi-layer structure for compact optical switching and modulation, and reconfigurable metamaterials. Terahertz THz quantum cascade laser QCL is a semiconductor based heterostructure laser based on intersubband transitions. Although THz QCLs have been developed with relatively high performance, there is always a need to further improve the device performance, for example, achieving high beam collimated, polarization arbitrarily controlled, and high speed modulation.
It is also desired that those performance could be achieved through an integrated approach for miniaturalization, easy alignment and reducing cost. In this presentation, we will demonstrate high collimated THz quantum cascade lasers through plasmonic collimation designs with a record beam divergence, electrically tunable THz polarizations by designing integrated THz metasurfaces on a hybrid dielectric-plasmonic waveguides, and broadband graphene-based integrated THz modulators with a fast modulating speed.
Spectrally broadband modulation of the THz transmission is obtained in the frequency range from 0. Conventional optical lenses focus electromagnetic waves by imparting position-dependent phase delay through shaping their geometry. This poses difficulties in eliminating the geometric aberrations in high numerical aperture lenses, in addition to the fabrication challenges when operating at short wavelengths e. In contrast, metasurfaces realize full control of phase through tailoring the subwavelength resonant structures, allowing for the demonstration ultrathin flat lens without suffering from geometric aberrations, although the efficiency is still rather low using single-layer metasurfaces.
Here we report the demonstration of high-performance flat lens in the terahertz frequency range using few-layer metasurfaces. Based on this success, we design, fabricate, and characterize a metasurface lens operating at 0. With a lens diameter and focal length both 5 cm, we realize a high numerical aperture of 0. Terahertz time-domain spectroscopy measurements show that the metasurface lens is capable of achieving the same signal intensity as compared to a TPX lens of the same diameter and focal length.
Surface plasmons SPs has promised a variety of cutting-edge applications. Recently, excitation of asymmetric SPs has drawn huge interest. It was realized either by engineering the phase gradient at the metal-dielectric interface, or by controlling the SP interference of two or more separated couplers. However, the coupling effects among the excitation units were usually ignored.
In this work, we presented an exotic approach in exciting asymmetric SPs in the terahertz regime by applying the free-space electromagnetically-induced-transparency EIT coupling mechanism. With the help of a near-field scanning terahertz microscope NSTM system, asymmetric level adjustable SP excitation and focusing were experimentally demonstrated.
Session Post: Poster Session. Come view the posters, ask questions, and network with colleagues in your field.
Citations per year
Authors of poster papers will be present to answer questions concerning their papers. Attendees are required to wear their conference registration badges to the poster session. This paper designed and implemented a set of infrared high-speed low noise intelligent test system based on OPENVPX standard, which is used to test the index, long term monitoring and life of infrared detector. Through testing and simulation, the results show that the system noise is less than uV, the dynamic range reaches dB, and the data throughput rate reaches 4Gbps, which can meet the requirements of the infrared detector test currently.
The hyperspectral images can not only provide the space information but also the spectral information. Pixels of interests generally incorporate information from disparate component that requires quantitative decomposition of these pixels to extract desired information. Oil spill detection can be implemented by applying hyperspectral camera which can collect the hyperspectral data of the oil.
By extracting desired spectral signature from hundreds of band information, one can detect and identify oil spill area in vast geographical regions. There are now numerous hyperspectral image processing algorithms developed for target detection. In this paper, we proposed a target detection algorithm for the identification of surface oil spills in ocean environment.
We present an accurate analyzing method based on multiple beam interference and Fresnel's formula that extract simultaneously the refraction index and the extinction coefficient from terahertz time domain spectroscopy transmission spectra with oscillations, which are the basis for calculating permittivity. Typical THz-TDS system worked in transmission mode is utilized for direct measurement of the transmission spectra with a frequency accuracy of 7. This paper proposes a novel wavefront-based algorithm for the beam simulation of both reflective and refractive optics in quasi-optical system.
The algorithm can be regarded as the extension to the conventional Physical Optics algorithm to handle dielectrics. Internal reflections are modeled in an accurate fashion, and coating and lossy materials can be treated in a straightforward manner.
Infrared and Millimeter Waves V11
A parallel implementation of the algorithm has been developed and numerical examples show that the algorithm yields sufficient accuracy by comparing with experimental results, while the computational complexity is much less than the full-wave. The algorithm offers an alternative approach to the modeling of quasi-optical system in addition to the Geometrical Optics modeling and full-wave method.
We propose a cost effective digitized radio-over-fiber DRoF system employing a sigma delta modulation SDM and a bidirectional transmission technique using phase modulated downlink and intensity modulated uplink. This makes the proposed system simpler and more cost-effective because a digital to analog converter DAC and light source can be avoided at the antenna station. The results also show the good error vector magnitude performance in both downlink and uplink signals after transmission over a km optical fiber link.
This paper implements an active terahertz wave imaging system combining terahertz wave transmitting and receiving with a Cassegrain antenna. The terahertz wave at the frequency of 94GHz is created by terahertz source, focused on the feed element for Cassegrain antenna by high density polyethylene HDPE lens, and transmitted to the human body by Cassegrain antenna. The reflected terahertz wave goes the same way it was emitted back to the feed element for Cassegrain antenna, focused on the horn antenna of detector by another HDPE lens.
The scanning section uses two-dimensional planar mirror. The tunability was in the range of 1. The maximum THz wave output energy was A periodically inverted quasi-phase-matched QPM GaAs crystal and a GaSe crystal were used to generate terahertz wave of micro-watt level by the difference frequency generation DFG method.
This provides a potential practical palm-top tunable THz sources for portable applications. Metamaterials with subwavelength structural features show unique electromagnetic responses that are unattainable with natural materials. We first present our studies of dipole arrays at terahertz frequencies. Then in L-shaped structure, we find an unusual-mode current resonance responsible for low-frequency characteristic dip in transmission spectra and attribute it to the resonance coupling and splitting under the broken symmetry of the structure. Using optical pump—terahertz probe method, we investigate the spectral and dynamic behaviour of optical modulation in the split-ring resonators.
The observed blue-shift and band-broadening could be explained by changed refractive index and conductivity in the photoexcited semiconductor substrate. To achieve broad band COMB operation in terahertz quantum cascade lasers, we presents the strategies and approaches of designing chirped Distributed Bragg Reflector DBR for group velocity compensation in metal-metal waveguide terahertz quantum cascade through 1D and 3D models. Our results show the geometric shape of the chirped corrugation periods plays an important role on the both the band width, the strength, and the smoothness of the group delay compensation curve in terahertz frequency range.
A two-section chirped DBR is proposed to provide smoother group delay compensation while still maintain the broad frequency range octave operation within 2 THz to 4 THz. Observe from long distance, most targets appear to be weak and small, such as missile, aircraft and vehicle. However, for missile guidance, locking the target in longer distance means more time would be used to control the flight of the missile, thus more chance to hit the target; for menace warning, detect the target in longer distance means more time to maneuver, thus more chance to survive.
This paper introduced a fast and effective method to detect small weak infrared target in complex background, which is suitable for missile guidance and menace warning. Classification of a hyperspectral image sequence amounts to identifying which pixels contain various spectrally distinct materials that have been specified by the user. Several techniques for classification of multi-hyperspectral pixels have been used from minimum distance and maximum likelihood classifiers to correlation matched filter-based approaches such as spectral signature matching and the spectral angle mapper.
In this paper, an improved hyperspectral images classification algorithm is proposed. In the proposed method, an improved similarity measurement method is applied, in which both the spectrum similarity and space similarity are considered. We use two different weighted matrix to estimate the spectrum similarity and space similarity between two pixels, respectively.
The spectral characteristics of infrared radiation from target provide significant characteristics information for target's detection and track including radiance brightness, radiance intensity and spectrum characteristics of target. And the same time, the spectral characteristics provide the basis of target detection and recognize equipment's waveband optimization design and detection capability analysis. This paper using the passive imaging Fourier transformation infrared spectrometer measure the infrared spectral characteristic of target.
The spectral range cover the medium wave and long wave infrared. This paper designs a set of calibration and test processes to realize the infrared spectral radiance measurement of target. Summary: In this paper, we used region covariance descriptor and calculated region covariance using integral images and the computational cost is independent of the size of the region. In matching stage, describe a new and fast pyramid matching algorithm under the distance metric, which performed extremely rapidly than a brute force search. The performance of region covariance descriptor is superior to other methods, and the pyramid matching algorithm performs extremely rapidly and accurately.
Furthermore, the method can be extended in several ways, such as infrared object recognition, tracking and image stabilization, classification.
Millimeter–wave Propagation Model (MPM) - ITS
Experimental results and human visual perception illustrate the effectiveness of the proposed image fusion. FTIR imaging spectrometer has significant meaning in the fields like industrial plume emission monitoring and public security monitoring. First, the structure and design of this spectrometer is indicated and discussed.
Based on the algorithms research, the related gas identification software is developed. To verify this design, both lab and field experiments are realized. The lab experiment is applied to verify the spectral identification algorithm. The field trial is applied to analyze the gas components, and the results show that this spectrometer can realize the gas elements identification in real time.
The infrared absorption spectrum of anhydrous glucose has been measured by Fourier transform infrared spectrometer FTIR. To investigate the physical specific structure and the molecular interaction in far-infrared band, the sample structure properties were analyzed meticulously by solid-state density functional theory DFT calculations. CASTEP quantum chemical calculation software package was utilized to simulate the infrared spectroscopy of glucose crystal structure based on periodic boundary condition and plane wave pseudopotential method.
The agreement between theory and experiment indicates that the crystal simulation calculation based on solid-state density functional theory can identify substance absorption peaks and vibration attribution accurately in THz region. The optical asynchronous sampling technique is the way to realize the fast detection of terahertz pulse. By researching, designing and experiment of this circuit.
As a result, the two lasers can phase locked on two repetition frequencies with a small frequency difference calculated by the circuit. Integrated cavity output spectroscopy ICOS is a very sensitive method of trace gas measurement. It is widely known as its extremely long optical path and characteristics of direct absorption. It adds modulation on the direct absorption so that achieves the noise suppression. We combine the ICOS method and WMS method to research the gas measurement using a narrow band tunable diode laser, and get several absorption peaks of carbon dioxide in air.
Terahertz THz spectroscopy is sensitive to probe several aspects of biological systems. In THz frequency, electrically controllable Drude-like intraband absorption makes graphene a promising platform for building graphene-based optoelectronic devices such as THz biosensor. In this work, BSA protein thin films were spin coated on single-layer graphene. IR lasers with different power were used as the pump light to stimulate the sandwich-like sample respectively.
The protein graphene monolayer complex conductivity was calculated using the transmission method. In this paper the novel optical properties of single-layer graphene and BSA protein on graphene in the range of 0. Microfluidic technology can control the fluidic thickness accurately in less than micrometers. So the combination of terahertz and microfluidic technology becomes one of the most interesting directions towards biological detection.
We designed microfluidic chips for terahertz THz spectroscopy of biological samples in aqueous solutions. Using the terahertz time-domain spectroscopy THz-TDS system, we experimentally measured the transmittance of the chips and the THz absorption spectra of threonine and arginine, respectively. The results indicated the feasibility of performing high sensitivity THz spectroscopy of amino acids solutions. Therefore, the microfluidic chips can realize real-time and label-free measurement for biochemistry samples in THz-TDS system.
The final goal of this work is to study the best parameter of coplanar waveguide CPW and micro-strip-line MSL in the terahertz on-chip system. The CPW is a structure in which all the conducting media are coplanar. The dielectric beneath the conductors need be sufficiently thick to prevent field leakage.
The MSL consist of a strip conductor and a ground plane separated by a dielectric medium. The material of dielectric layer is benzocyclobutene BCB in our experiment. The simulation results show that the scattering parameters of the two waveguides are similar to the known literatures. Therefore, our simulation work can accelerate the fabrication progress of the on-chip THz system.
The core methodology is that in the deep understanding and research of the photoelectric information control, the basic theory of the spatial light modulator and the algorithm based on space-time adaptive system is discussed deeply which used to the core of the photoelectric system configuration by which key components applied to solve the control function. This paper discusses the hardware system. Usually, an SLM modulates the intensity of the light beam.
However, it is also possible to produce devices that modulate the phase of the beam or both the intensity and the phase simultaneously. Besides, the discuss includes the control on the SLM for spatial information of the amplitude, phase, frequency, polarization, and the intensity of energy research. A typical model is used to illustrate the feasibility, and the criteria is developed. Multiply pages text information hidden in an envelope can be observed clearly and by utilizing the frequency modulation continuous wave terahertz imaging technology.
The delay time between the probe and reference signal was calculated and then the positions of the object in depth were estimated. The phase information and two-dimensional scanning were combined together to obtain the three-dimensional tomographic imaging data. Layer resolution is better than 1mm. The spatial resolution is 1 mm. Layered images can clearly show the text at the different page. A photo-excited tunable and broadband metamaterial absorber in the terahertz region is proposed.
The metamaterial absorber is composed of three layers like the sandwich, the top layer is acirclr metal-semiconductor circle split ring and the bottom layer is a metallic ground plane, these two layers are separated by a dielectric spacer, which we choose as the polyimide. The conductivity of the silicon can be tuned actively with the incident pump power. We use the full wave simulation and the equivalent circuit model to analysis this absorber, and interpreted the phenomena showed when the conductivity of the silicon filled in the gap of ring is changed by the surface current and the electric field.
The proposed equivalent circuit model can save more time to design this kind of absorber in need. The proposed photo-excited tunable metamaterial absorber can also be used as terahertz modulators and switches. Both the stationary-phase method and finite element method are used to analyze and simulate the characteristics of the proposed device. To give comprehensive understanding, the position of the reflected terahertz wave beam is verified in simulation by using the COMSOL Multiphysics software.
Numerical calculation results show that the proposed terahertz wave switch a high extinction ratio 35dB for TE polarization and 30dB for TM polarization. This provides an attractive way for creating a simple structure and compact size terahertz wave switch with acceptable extinction ratio. We present an ultra-compact gate-voltage-controlled terahertz power divider based on graphene plasmonic waveguide, which consists of five graphene ribbons embedded in the polymethylmethacrylate PMMA substrate.
We have theoretically explained their mechanisms as bias voltage change induced carrier density of graphene modification and the coupling coefficients of graphene plasmon effect after carrier density change, respectively. The surface plasmonic polariton SPP propagation and extinction ratio in the graphene-based device are numerically investigated.
The proposed terahertz power divider has a 3dB working band about 0. It anticipated that our proposed compact device is potentially interesting for the terahertz wave integrated circuit technology. Principal component analysis PCA was adopted to extract principal components, according to distributions of two PCs within PC1, PC2 and PC3 in two-dimensional planes, distribution areas of three varieties of pepper seeds were divided in each two-dimensional plane.
Such the four kinds of rhubarb processed products as samples, using terahertz spectroscopy system to measure characteristics data of each sample, combined terahertz wave characteristics with chemometrics, we classify rhubarb by category, and combining the characteristics of the material basis of changes in cooked rhubarb process, we not only achieved a qualitative study of traditional Chinese medicine processed products with terahertz spectroscopic techniques, but also obtained the law of substances quality variation of tanning and anthraquinone in rhubarb before and after processing, and in accordance with results of thin layer chromatography.
Aiming at the dual-band THz images, this paper use BM3D de-noising algorithm to filter noise and correct the scanning problem. Use intensity-base registration algorithm to correct the problems of translation, rotation and scaling which exist between the two images, register the two images. And after enhanced by the adaptive histogram equalization algorithm, the images are fused by image fusion algorithm based on wavelet. This method effectively reduce the image noise, scan distortion and matching error, improve the details, enhance the contrast. It is helpful to improve the detection efficiency of hidden objects too.
Lidar is short for light detection and ranging, which has caused more and more attention to study it. Because the accurate wind information can be used not only in weather report, but also the safety guarantee of the airplanes. In this paper, a more detailed signal model of wind measurement lidar is proposed.
It includes the laser transmitting part which is described the broadening of the spectral, the laser attenuation in the atmosphere, the backscattering signal and the detected signal. This signal model can describe the system more accurate and more detailed, so that the following work will be easier and more efficient. The scattering properties of suspended particles in water is key for water quality measurement.
In this paper, we choose a typical suspended particle, alga, to study its intensity distribution of scattering light based on T-matrix theory and three kinds of irregular shape model: spheroid, finite circular cylinder and generalized Chebyshev are simulated. The relationship between intensity of scattering light and scattering angle, wavelength of incident light, are calculated.
Simulation results show that most scattering light mainly focus on the forward direction and there is a decreasing trend with the increase of scattering angle and wavelength. Terahertz THz radiation has the higher penetration to clothing, cardboard boxes, plastic packaging materials and other similar dielectrics. Its lower photon energy compared with X-rays make the detected material and the human being to be not destroyed. THz application in field of security are developed by many countries.
In this research, we present a multiband of passive terahertz imaging by the thermal radiation measurement. The result shows that NETD of the passive imaging system is 0. We found that the main source of noise is the noise from detection circuit. Finally, the improvement methods of detecting sensitivity are analyzed and discussed. With the bandwidth of 12 GHz, a 0. Based on the small rotate angle and the far field approximation, the Range-Doppler algorithm is used in the simulation of ISAR imaging.
The simulation results show that THz stepped-frequency radar can achieve high resolution ISAR images of aircraft, the resolution of ISAR images can reach centimeter-scale, which laid a theoretical foundation for radar imaging in THz band. Signal processing is one of the main parts of any radar system. Different signal processing algorithms are used to extract information about different parameters like range, speed, direction etc, of a target in the field d of radar communication. This paper presents LFM Linear Frequency Modulation pulsed radar signal processing algorithms which are used to improve target detection, range resolution and to estimate the speed of a target.
For hardware implementation pipeline optimization is adopted and also other factors are considered for resources optimization in implementation process. Focusing algorithms in this work for improving target detection, range resolution and speed estimation are hardware optimized fast convolution processing based pulse compression and pulse Doppler processing.
Friday 14 October Show All Abstracts. Session 7: Infrared. Infrared optical spectroscopy is a powerful tool for many applications including material analysis, environmental sensing, health diagnostics and others. One of the greatest and most important uses of millimeter waves is in transmitting large amounts of data. Every kind of wireless communication, such as the radio , cell phone , or satellite , uses specific range of wavelengths or frequencies.
For example, a telephone conversation requires only about 6 kHz of bandwidth, while a TV broadcast, which carries much larger amounts of information, requires about 6 MHz.
A kilohertz, is one thousand cycles per second; a megahertz is one million cycles per second. Increases in the amount of information transmitted require the use of higher frequencies.
- International Journal of Infrared and Millimeter Waves | Publons.
- Journal of Infrared, Millimeter, and Terahertz Waves - Wikipedia!
- European Integration and Political Conflict (Themes in European Governance).
This is where millimeter waves come in. Their high frequency makes them a very efficient way of sending large amounts of data such as computer data, or many simultaneous television or voice channels. Radar is another important use of millimeter waves, which takes advantage of another important property of millimeter wave propagation called beamwidth. Beamwidth is a measure of how a transmitted beam spreads out as it gets farther from its point of origin.
In radar, it is desirable to have a beam that stays narrow, rather than fanning out. A carefully designed antenna allows microwaves to be focused into a narrow beam, just like a magnifying glass focuses sunlight Unfortunately, small beamwidths require large antenna sizes, which can make it difficult to design a good radar set that will fit, for example, inside a cramped airplane cockpit. A radar sensor used in model Mercedes S-class automobiles. The circuits that transmit and receive millimeter waves are housed beneath the dome-shaped plastic "radome," which is about 10 cm 4 inches in diameter.
This unit is mounted behind a portion of the car's hood that is made to be transparent to millimeter-wave energy. But the use of millimeter-length microwaves has allowed engineers to overcome this antenna problem. For a given antenna size, the beamwidth can be made smaller by increasing the frequency, and so the antenna can be made smaller as well.