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.
Guided wave techniques have proven to be an outstanding technique for THz sensing and spectroscopy applications. Here, we report on a cylindrical-based guided wave structure that omits the need for high index silicon lenses, showing good performance in both TM and TE propagational modes.
Terahertz time-domain spectroscopy can be used to detect the thickness of thin dielectric layers by measuring the relative pulse delay of the propagating terahertz pulse. The detection limit was considerably increased by using the high filling factor of a 2-cylinder waveguide sensor. The single-pass delay was increased by a factor of more than 150 for dielectric layers down to 2.5 microns thickness...
We present a nanosecond optical parametric oscillator for terahertz generation in periodically poled lithium niobate. The used QPM-scheme based on periodic poling leads to a collinear pump and signal wave and an emission of the terahertz wave under the well known Cherenkov-angle.
We present recent progress in on-the-fly broadband raster transmission and reflection terahertz imaging with a focus on the data evaluation. Possibilities to enhance the resolution by frequency domain filtering as well as terahertz tomography are discussed.
A nanosecond OPO pumped by a Q-switched Nd:YVO4 laser for terahertz generation in periodically poled lithium niobate with a new pattern is presented. Characteristic properties of the OPO including cascaded processes are discussed.
Terahertz spectroscopy has become a well-established tool under laboratory conditions but terahertz stand-off detection in the real world is hampered by a number of influences related to the environment and the sample properties such as air humidity, surface roughness and angle of detection. A terahertz stand-off system must be calibrated in order to account for these influences. We have performed...
We report on terahertz wave generation using transient photoconductivity induced by femtosecond laser pulses in semiconductor surfaces. In particular the dependence of terahertz emission characteristics on pump pulse parameters like diameter and input angle is investigated in detail both experimentally and theoretically. It is shown that the emission in forward (quasi-optical reflection) as well as...
A high speed optical delay line in combination with a fiber-coupled terahertz time domain spectroscopy system allows for scan rates up to 200 Hz, a spectral resolution of about 10 GHz and a bandwidth of 3 THz.
A nanosecond OPO pumped by a single mode Q-switched Nd:YVO4 laser for terahertz generation in slant stripe periodically poled lithium niobate is presented. The oscillation threshold is overcome by stabilized pump enhancement and lowered by means of injection seeding by a grating stabilized, tunable diode laser.
The potential of short terahertz pulses for thin-film measurements of materials opaque in the visible range is demonstrated. Layer thicknesses down to 10 mum have been determined in transmission as well as in reflection measuring mode and complex multilayer structures in the sub-wavelength range have been resolved with this technique.
We report on an actively controlled enhancement cavity for terahertz generation using optical rectification in lithium niobate. By recycling the transmitted fundamental laser power from a Ti:Sapphire laser an increased pump power is available for the nonlinear process. Therefore a much higher THz signal is obtained in relation to single-pass geometry. Terahertz intensities generated by different emitters...
Optical rectification of femtosecond pulses in nonlinear materials is an efficient method to generate ultra-short terahertz (THz) pulses in a wide frequency range extending from 100 GHz to well above 10 THz. Lithium niobate (LN) is well suited for such a purpose despite the high absorption in the THz range. In this part we will focus on the various experimental realizations to produce THz radiation...
Optical rectification of femtosecond pulses in nonlinear materials is an efficient method to generate ultra short terahertz (THz) pulses over a wide frequency range extending from 100 GHz to well above 10 THz. Lithium niobate is particularly well suited for such purposes and can be used both in bulk and periodically poled forms. Different optical techniques for the generation of THz pulses are presented...
Different methods of optical THz generation in pure and MgO-doped lithium niobate crystals using nonlinear methods and fs-laser radiation are reported. The concepts discussed here include optical rectification (OR) and generation of Cherenkov radiation in bulk and periodically poled lithium niobate as well as the use of slanted and aperiodically poled crystals. The experimental realization as well...
We report on the efficient Cherenkov-type terahertz (THz) generation using lithium niobate crystals and a high repetition rate femtosecond laser. An actively length controlled synchronously pumped ring resonator acts as an enhancement cavity for the near infrared pump and therefore recycles the available pump power towards a higher terahertz output. A seven times higher THz field amplitude was measured...
In this paper we describe the generation of terahertz radiation using different photonic techniques. The methods discussed here include surface emission from semiconductor surfaces in an external magnetic field as well as nonlinear generation in lithium niobate crystals, in particular, Cherenkov radiation and optical rectification in unpoled and poled lithium niobate (PPLN). Typical applications utilizing...
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.