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 performed THz pulse generation and detection beyond 4 THz by using a 1.04-μm Yb-doped fiber laser with a pulse duration of 480 fs. Owing to higher-order nonlinear processes in LiNbO3 crystals, THz pulses can be emitted with a bandwidth extending beyond the excitation pulse limitation. Emitted THz pulses are detected by using a stable sampling pulse that is temporally compressed by an optical fiber.
Metamaterial-based waveguides offer unusual phenomena compared to conventional metallic and dielectric waveguides. We present a novel waveguide based on metamaterials, an air-core waveguide with a magnetic metamaterial cladding assembled from split ring resonator fibers. The transmission properties of the waveguide in the terahertz region are characterized both experimentally and numerically. Such...
Although small in volume, debris on the airport surface may cause severe damage to aircraft. To detect these obstacles, we have been developing optically-connected airport surface foreign object debris (FOD) detection 96 GHz millimeter-wave radar systems. The proposed runway surface FOD detection system will be installed in airports. This paper discusses the evaluation results of radio-over-fiber...
This paper presents a real-time error-free 30-Gbit/s transmission at over 10-m distance using a 300-GHz-band coherent system. Frequency and phase stabilized carrier signals are photonically generated with use of an optical frequency comb and an integrated optical filter/combiner light-wave circuit.
In a continuous-wave terahertz spectrometer, we employ photomixing of three lasers, allowing us to measure at three terahertz frequencies simultaneously. Whilst two of the terahertz frequencies can be tuned to obtain terahertz spectra, one terahertz frequency remains fixed. The data recorded at the fixed frequency is used to normalize the spectra of the two other frequencies. As a result, the accuracy...
We constructed a widely and continuously tunable terahertz frequency synthesizer traceable to a microwave frequency standard. Photomixing of two optical frequency synthesizers, linked to the frequency standard via dual optical frequency combs, makes this THz synthesizer traceable to the frequency standard. To demonstrate the potential of wide and continuous tunability in the THz synthesizer, we tuned...
A compact, easily tunable terahertz burst emission system based on the mixing of two linearly chirped pulses in Michelson interferometer was investigated. The use of linearly chirped optical pulses ejected straight from the picosecond fiber laser enabled us to avoid bulky external optical pulse stretching schemes. System operation range determined from the power measurements reached up to 2.4 THz.
In this study we discuss the influence of the state of degradation, the three-dimensional fibrous structure and the presence of calcium compounds on terahertz absorption properties of historic parchment in the interval 45–85 cm−1, based on the analysis of 32 archival parchment samples, with terahertz time-domain spectroscopy in transmission mode, optical microscopy and Fourier-transform infrared spectroscopy...
Whispering gallery mode (WGM) resonators have high Q factors and small modal volumes and can thus show strong non-linear interactions. Most of the interesting non-linear materials are crystalline and feature high refractive indices such that efficient coupling to the resonator is challenging. We present a study on high refractive index WGM resonators and show that coupling via a crystalline dielectric...
We propose a 600 GHz data transmission of high definition television using the combination of a photonic emission using an uni-travelling carrier photodiode and an electronic detection, featuring a very low power at the receiver. Only 10 nW of THz power at 600GHz were sufficient to ensure real-time error-free operation. This combination of photonics at emission and heterodyne detection lead to achieve...
We demonstrate that the photonics-based balanced self-heterodyne system enables us to measure the phase change of the continuous terahertz-wave with the theoretical uncertainties limited by the signal-to-noise ratio (SNR) of the amplitude measurement. Although our system is based on free-running lasers and fiber components, excess phase noise can be cancelled out. When the SNR was 44 dB, the standard...
A novel THz hollow-core optical fiber is proposed using as a reflector a hyperuniform disordered network of dielectric cylinders connected with thin dielectric walls.
We have developed a THz synthesizer to generate a THz continuous wave based on a broadband optical frequency comb. Using the stimulated Brillouin scattering of a long optical fiber, only two optical modes are selectively extracted from the optical comb and a highly accurate THz continuous wave is generated by photomixing. In generation of 100GHz and 700GHz waves, fractional frequency instability of...
Generation of broadband optical comb with high OSNR was demonstrated by a combination of a Mach-Zehnder-modulator-based flat comb generator and a nonlinear fiber. To generate broadband combs with high OSNR, we compared three types of nonlinear fibers; a dispersion-flattened dispersion-decreasing fiber (DF-DDF), a dispersion-flattened fiber (DFF) and a highly nonlinear, dispersion-shifted fiber (HNL-DSF)...
High-speed coherent transmission at 325 GHz is successfully demonstrated with a 20-Gbaud QPSK signal. A frequency-locked terahertz signal can be provided by an optical-modulation-based optical frequency comb signal. A high-gain antenna with a gain of 46 dBi is suitable to extend the transmission distance up to 15 m without requiring a terahertz amplifier.
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.