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Contact person |
József A. Fülöp |
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The HE-THz source provides strong-field single-cycle pulses in the low-frequency part of the THz spectrum for field-driven experiments at 50 Hz rep rate. The electric-field waveform of the THz pulses is fully characterised by electro-optic sampling.
Intense THz pulses can drive selected degrees of freedom in matter into regimes far beyond the small-perturbation limit. This feature has enabled new applications that can roughly be classified in terms of nonlinear spectroscopy (providing insights into the nature of the driven mode) and materials control (driving the system into a target state). The HE-THz source is a unique tool for accessing a new regime of THz-matter interaction in experiments requiring high THz field at low frequency for studying THz-induced strong-field phenomena.
The High-Energy Terahertz Source (HE-THz, Fig. 1) is driven by a multi-100-mJ femtosecond pump laser and consists of two main units: the THz source and the electro-optic sampling unit (Fig. 2).
Figure 1: The cryogenically cooled LiNbO3 prism (THz generator crystal) inside the vacuum chamber.
Figure 2: Block scheme of the High-Energy Terahertz Source (HE-THz).
Pump laser.
The so-called THz pump high-energy pump laser operates at 1030 nm wavelength. The laser delivers up to 500 mJ pulse energy at 50 Hz repetition rate. The pulse duration is 500 fs. The laser is equipped with a synchronised Ti:S arm that enables further pump-probe arrangements (1 kHz, 4 mJ, 100 fs).
THz source.
THz pulses are generated by optical rectification of the optical pump pulses in a large, cryogenically cooled LiNbO3 prism (Fig. 1), using the tilted-pulse-front technique. Single-cycle THz pulses are generated and tightly focused to achieve a peak electric field strength of 1 MV/cm at the sample. The THz pulse energy at the sample is up to 350 μJ.
Electro-optic sampling.
A small portion of the optical beam provides the sampling pulses for electro-optic sampling to measure the electric-field waveform of the THz pulses transmitted through the sample. The spectral amplitude and phase can be obtained by Fourier transformation.
Specifications
Optical pump pulse parameters:
| Central wavelength | 1030 nm |
| Pulse duration | 500 fs |
| Pulse energy | up to 500 mJ |
| Repetition rate | 50 Hz |
| Energy stability | < 2% (rms) |
THz pulse parameters:
| Pulse energy at sample | 350 μJ |
| Spectral maximum | 0.25 THz |
| Useful Spectral coverage | 0.1 THz – 1 THz |
| Peak THz electric field | 1 MV/cm |
Electro-optic sampling:
| Minimal detectable field | 100 kV/cm |
| Useful Spectral coverage | 0.1 THz – 1.5 THz |
| Signal-to-noise ratio | > 200:1 (depending on measurement time) |
Sample parameters:
| Minimum sample clear aperture | 5 mm |
| Temperature range |
Room temperature. Please contact us for further possibilities. |
| Measurement modes |
THz transmission. Please contact us for further possibilities. |
Samples can be investigated in transmission geometry. The sample can be placed into the focus of the THz beam. Other arrangements are also possible.
No specific non-standard target system is available. The THz beam can be focused onto a user sample.
Calibrated pyroelectric detector for THz pulse energy measurement.
Electro-optic sampling for THz waveform measurement.
[1] J. A. Fülöp, Z. Ollmann, Cs. Lombosi, C. Skrobol, S. Klingebiel, L. Pálfalvi, F. Krausz, S. Karsch, J. Hebling, “Efficient generation of THz pulses with 0.4 mJ energy,” Opt. Express 22, 20155 (2014).
[2] J.A. Fülöp, L. Pálfalvi, M.C. Hoffmann, J. Hebling, “Towards generation of mJ-level ultrashort THz pulses by optical rectification,” Opt. Express 19, 15090 (2011).
[3] J.A. Fülöp, L. Pálfalvi, G. Almási, J. Hebling, “Design of high-energy terahertz sources based on optical rectification,” Opt. Express 18, 12311 (2010).
[4] J. Hebling, G. Almasi, I. Z. Kozma, and J. Kuhl, “Velocity matching by pulse front tilting for large area THz pulse generation,” Opt. Express 10, 1161 (2002).