The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
We report saturable absorption in multilayer epitaxial graphene at 4.7 μm wavelength using mid-infrared quantum cascade laser. From z-scan and differential transmittance measurements, we demonstrate an enhancement of the transmittance of 9 %, attributed to the Pauli blocking effect in the graphene layers. We found that the saturation intensity is in the range of MW/cm2. Our results show the potential...
Most semiconductors have surface dynamics radically different from its bulk counterpart due to the surface state. However, direct observation of the surface carrier dynamics has been limited to nano structures where the surface-to-volume ratio is very high. Here, we develop a new type of terahertz (THz) nanoscopy to investigate surface dynamics of bulk semiconductors, using metallic nano gap accompanying...
The absorption spectra of the dermis and epidermis were measured in a terahertz band from 0.2 to 2 THz. The absorption magnitude of the dermis was higher than that of the epidermis owing to the inclusion of collagen fibers. The absorption of the dermis decreased upon heating at high temperature, and this tendency was similar to that of a collagen sheet. This finding suggests that the condition of...
In situ and remote detection of chemical product is experimentally demonstrated using a continuous-terahertz (THz) wave sensing/imaging system with a Teflon pipe as a scanning arm. Based on THz-refractive-index-sensitive reflection and fast response of electronic THz detector, the reflective THz sensing system can be used to real-time trace and quantitatively analyze the ammonium-chloride aerosols...
Passive imaging cameras at sub-millimeter wavelengths are currently entering a new era with the development of large format arrays of direct detectors. Several of these arrays are being developed with bare absorbing meshes without any antenna coupling (lens or horn) structures. This paper uses a spectral electromagnetic model to analyze the performance of absorber based focal plane arrays in comparison...
We present an experimental demonstration of three-dimensional terahertz radar based on multi-directional leaky-wave scanning. The radar consists of a leaky-wave antenna that allows for one-dimensional beam steering by sweeping frequency around 300 GHz. The 3D positions of objects placed in front of the antenna can be reconstructed by synthesizing radar signals acquired at various azimuthal angles...
A dual-band millimeter-wave cloud radar is studied in this paper. Firstly, the available frequencies for the dual-band operation are analyzed, including several atmospheric window, such as 94 GHz, 140 GHz and 220 GHz. Then, the equivalent radar cross section of the particles in cloud are studied, which is dependent on the particle' size and available frequencies. Based on the above analysis, 94 GHz...
This work presents a novel focal plane module architecture based on kilo-pixel arrays able to image from UV to far-infrared scenes. The focal plane arrays are integrated with custom-made, chopper-stabilized read-out integrated circuits into sub-assembly modules to be mounted on the optical telescope of the instrument.
THz radiation is strongly absorbed, as well as reflected, by water. This spectral feature can be exploited to detect the presence of water under the surface of mural paintings and mosaics. In this study we report on the capability of our 3D reflective THz imaging system to detect water under samples simulating a fresco or a mosaic.
We present an investigation related with the use of sialic acid as an auxiliary indicator for the early detection of diseases by using Terahertz Frequency-Domain Spectroscopy (THz-FDS) Technique. We propose the characterization of thin films of N-Acetylneuraminic acid-synthetic, >95% and add in colloidal solution nanoparticles of Ag (Ag-NPs) and Au (Au-NPs) in order to increase the superficial...
In this work, the terahertz (THz) absorption spectra of a typical protein BSA (Bovine Serum Albumin) in aqueous solution were measured under different pH conditions. The temporal changes in the absorption spectra were analyzed using the two-dimensional correlation spectroscopy (2DCOS). By comparing the cross peaks corresponding to the different pH values, it can be obtained that the conformation is...
Metal-stripe surface grating structure presents a stable single-mode operation for THz quantum cascade lasers due to its strong coupling mechanism and easy tuning. We use sampled metal-stripe gratings to establish a distributed feedback and scale the single-mode power by tune the grating parameters. Record single-mode power more than 500 mW at 10 K is achieved.
Photonic and electronic integration technology is pushed forward strongly by the telecommunication market to reduce the size and the costs of each component. Electro-optical terahertz (THz) technology based on the communication wavelength of 1.55 μm can directly benefit from the development of these integration techniques. Thus, continuous wave (cw) THz spectroscopy systems bear great potential to...
We present the first direct observation of 26.5 GHz direct modulation of mid infrared buried heterostructure quantum cascade laser (QCL) emitting at 9 μm. For these measurements we have used an ultra-fast QWIP detector with 65 GHz bandwidth. As expected the modulation frequency bandwidth increases by increasing the laser driving DC current. Finally, we demonstrate that the laser cavity round trip...
Dispersion compensation is vital for the generation of ultrashort and single cycle pulses from modelocked lasers across the electromagnetic spectrum. However, no such scheme have been successfully applied to terahertz (THz) quantum cascade lasers (QCL) for short and stable pulse generation in the THz range. Here we show a monolithic on-chip compensation scheme for a modelocked QCL, permitting THz...
We report on Doppler-free spectroscopy using a free-running terahertz quantum-cascade laser at 3.3 THz in a pumpprobe configuration with a fast Ge:Ga detector. The sensitivity of the setup allows for the observation of a Lamb dip in deuterated water with a resolution of less than 1 MHz and an acquisition time of only 10 ms.
We present optimized THz detectors based on AlGaN/GaN field-effect transistors with integrated broadband bow-tie antennas (bow-tie TeraFETs). Designed with a comprehensive circuit model and fabricated with a recently developed AlGaN/GaN MMIC process, the devices reach a performance at room temperature which hitherto has only been achieved with Si CMOS TeraFETs. Capable of broadband detection from...
Influence of THz waves resonant to molecular vibrations to coherent Raman signal is studied by using THz time-domain coherent Raman spectroscopy. Enhancement of coherent Raman signal in THz region is observed depending on the intensity and polarization of irradiated THz waves.
His letter introduces a design of quadrupler at 330GHz and doubler at 165GHz based on one stage multiplier with anti-parallel Schottky varactors. For experimental verification, there are three DUT modules: 165GHz and 330GHz two bands output passive network, high-Octave CSMRs low pass filter and multiplier module. Measurement results show that: the maximum output power is more than 5.9mW at 165GHz...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.