Abstract-Efficient semiconductor source of multicycle terahertz pulses using intensity-modulated pump

Gy. Tóth, P. S. Nugraha, G. Krizsán, M. I. Mechler, Gy. Polónyi, J. Hebling,  J. A. Fülöp

https://www.osapublishing.org/abstract.cfm?uri=CLEO_AT-2018-JTh2A.191

Up to 5% conversion efficiency is predicted by numerical simulations for optimized GaP contact-grating THz sources based on optical rectification. Easy control of multicycle THz waveforms is enabled by a flexible dual-chirped OPA pump source.

© 2018 The Author(s)

Abstract-Mapping the lattice-vibration potential using terahertz pulses

C. Korpa, Gy. Toth, J. Hebling

(Submitted on 14 Jul 2017)

https://arxiv.org/abs/1707.04409

We develop a method for mapping the anharmonic lattice potential using the time-dependent electric field of the transmitted pulse through thin sample supported by a substrate of non-negligible thickness. Assuming linear propagation in the substrate we fully take into account internal reflection in it while the sample can show arbitrary nonlinear response. We examine the effect of frequency averaging appropriate for broad-band pulse and compare the results taking into account the full frequency dependence. We illustrate the procedure applying it to a model based on recently observed ferroelectric soft-mode nonlinearity in SrTiO3.

Abstract-High-energy terahertz pulses from semiconductors pumped beyond the three-photon absorption edge

Gy. Polónyi, B. Monoszlai, G. Gäumann, E. J. Rohwer, G. Andriukaitis, T. Balciunas, A. Pugzlys, A. Baltuska, T. Feurer, J. Hebling, and J. A. Fülöp

A new route to efficient generation of THz pulses with high-energy was demonstrated using semiconductor materials pumped at an infrared wavelength sufficiently long to suppress both two- and three-photon absorption and associated free-carrier absorption at THz frequencies. For pumping beyond the three-photon absorption edge, the THz generation efficiency for optical rectification of femtosecond laser pulses with tilted intensity front in ZnTe was shown to increase 3.5 times, as compared to pumping below the absorption edge. The four-photon absorption coefficient of ZnTe was estimated to be 𝛽4=(4±1)×10−5${\beta }_4=\left(4\pm 1\right)\times {10}^{-5}$ cm5/GW3. THz pulses with 14 μJ energy were generated with as high as 0.7% efficiency in ZnTe pumped at 1.7 µm. It is shown that scaling the THz pulse energy to the mJ level by increasing the pump spot size and pump pulse energy is feasible.

© 2016 Optical Society of America

Full Article  |  PDF Article

Abstract-Highly efficient scalable monolithic semiconductor terahertz pulse source

J. A. Fülöp, Gy. Polónyi, B. Monoszlai, G. Andriukaitis, T. Balciunas, A. Pugzlys, G. Arthur, A. Baltuska, and J. Hebling
https://www.osapublishing.org/optica/abstract.cfm?uri=optica-3-10-1075

Intense pulses at low terahertz (THz) frequencies of 0.1–2 THz are an enabling tool for constructing compact particle accelerators and for strong-field control of matter. Optical rectification in lithium niobate provided sub-mJ THz pulse energies, but it is challenging to increase it further. Semiconductor sources suffered from low efficiency. Here, a semiconductor (ZnTe) THz source is demonstrated, collinearly pumped at an infrared wavelength beyond the three-photon absorption edge and utilizing a contact grating for tilting the pump-pulse front. Suppression of free-carrier absorption at THz frequencies in this way resulted in 0.3% THz generation efficiency, two orders of magnitude higher than reported previously from ZnTe. Scaling the THz energy to the mJ level is possible simply by increasing the pumped area. This unique THz source with excellent focusability, pumped by novel, efficient infrared sources, opens up new perspectives for THz high-field applications.

© 2016 Optical Society of America

Full Article  |  PDF Article

Abstract- Possibility of high-energy THz generation in LiTaO3

L. Tokodi, A. Buzády, J. Hebling, L. Pálfalvi,

http://link.springer.com/article/10.1007/s00340-016-6513-x

Due to the absence of the detrimental three-photon absorption, LiTaO3 is a promising crystal for terahertz generation when pumping with an 800-nm pump wavelength. The nonlinear optical, photorefractive and dielectric (except the bandwidth) properties at the optical and the terahertz wavelength are very similar to those of LiNbO3. The absorption coefficient and refractive index spectra of 1 mol% Mg-doped stoichiometric LiTaO3 measured by terahertz time domain spectroscopy are presented. Optimization calculations have been performed, and results for a hybrid-type high-energy terahertz source using LiTaO3 are presented. About 90 % diffraction efficiency is predicted with a practically feasible contact grating.

Abstract-Hybrid tilted-pulse-front excitation scheme for efficient generation of high-energy terahertz pulses

L. Pálfalvi, Z. Ollmann, L. Tokodi, and J. Hebling
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-8-8156

Conception of a hybrid type tilted-pulse-front pumping scheme for the generation of high-energy terahertz pulses is presented. The proposed setup is the combination of the conventional setup containing imaging optics and the contact grating. The solution was developed for nonlinear materials requiring large pulse-front-tilt angle, like LiNbO3. Due to the creation of the pulse-front-tilt in two steps the limitations of imaging errors can be significantly reduced. Furthermore the necessary grating constant of the contact grating can be larger compared to the simple contact grating scheme making possible the fabrication of the grating profile with significantly higher precision. A detailed optimization procedure with respect to the diffraction efficiency on the contact grating is given for LiNbO3. Instructions are also given how to construct the geometry of the setup in order to minimize imaging errors. Examples are given for LiNbO3 based practically realizable, optimized schemes with reduced imaging errors and high diffraction efficiency on the contact grating.

© 2016 Optical Society of America

Full Article  |  PDF Article

Abstract-Hybrid tilted-pulse-front excitation scheme for efficient generation of high-energy terahertz pulses

L. Pálfalvi,1,* Z. Ollmann,1,2 L. Tokodi,1 and J. Hebling1,2,3 

1Institute of Physics, University of Pécs, Ifjúság ú. 6, 7624 Pécs, Hungary
2Szentágothai Research Centre, University of Pécs, Ifjúság ú. 20, 7624 Pécs, Hungary 3MTA-PTE High-Field Terahertz Research Group, University of Pécs, Ifjúság ú. 6, 7624 Pécs, Hungary *palfalvi@fizika.ttk.pte.hu 

https://www.osapublishing.org/DirectPDFAccess/679F1BB3-96C9-FEBF-9D4708D5CB3C835B_338821/oe-24-8-8156.pdf?da=1&id=338821&seq=0&mobile=yes

Abstract: Conception of a hybrid type tilted-pulse-front pumping scheme for the generation of high-energy terahertz pulses is presented. The proposed setup is the combination of the conventional setup containing imaging optics and the contact grating. The solution was developed for nonlinear materials requiring large pulse-front-tilt angle, like LiNbO3. Due to the creation of the pulse-front-tilt in two steps the limitations of imaging errors can be significantly reduced. Furthermore the necessary grating constant of the contact grating can be larger compared to the simple contact grating scheme making possible the fabrication of the grating profile with significantly higher precision. A detailed optimization procedure with respect to the diffraction efficiency on the contact grating is given for LiNbO3. Instructions are also given how to construct the geometry of the setup in order to minimize imaging errors. Examples are given for LiNbO3 based practically realizable, optimized schemes with reduced imaging errors and high diffraction efficiency on the contact grating.