Fig 1 - uploaded by François Blanchard
Content may be subject to copyright.
Source publication
We demonstrate the generation μJ-level, single-cycle terahertz pulses by optical rectification from a large-aperture ZnTe single crystal wafer. Energies up to 1.5 μJ per pulse and a spectral range extending to 3 THz were obtained using a 100 Hz Ti:sapphire laser source and a 75-mm-diameter, 0.5-mm-thick, (110) ZnTe crystal, corresponding to an aver...
Context in source publication
Context 1
... ALLS beam line used in these experiments provided 800 nm, 30 fs laser pulses with energies as high as 48 mJ (at the ZnTe crystal position) at a repetition rate of 100 Hz. The experimental setup, as shown in Fig. 1, is comprised of three main parts: a THz generation chamber held under vacuum (∼10 -6 torr), an 800-nm probe beam propagating in air, and a dry- N 2 -purged electro-optic (EO) sampling detection line. The THz emitter consisted of a 0.5- mm-thick (110) ZnTe single crystal wafer with a diameter of 75 mm (Nikko Materials). To minimize ...
Similar publications
Recent high energy density thin film material development has led to an increased interest in pyroelectric energy conversion. Using state-of-the-art lead-zirconate-titanate piezoelectric films capable of withstanding high electric fields we previously demonstrated single cycle energy conversion densities of 4.28 J/cm³. While material improvement is...
SrMgF4 has an extremely large bandgap Eg of 12.50 eV as obtained from reflection dispersion. The symmetry of this crystal is monoclinic P21 at room temperature and transforms to orthorhombic Cmс21 phase near 478 K as temperature increases. Acentric character of the low-temperature (LT) phase is confirmed by pyroelectric luminescence at T < 440 K. T...
It has now been determined that the pyroelectric properties of lithium niobate crystals affect thecharacteristics of nonlinear optical effects observed in such crystals [1–3]. From the standpoint of application of these crystalsin modern photonic devices, of special interest is the idea of pyroelectric compensation of diffraction spread of the ligh...
Citations
... Figure 3(a) displays the extracted time-domain terahertz waveform after the time-axis calibration has been performed for laser output pulse energies of 120, 20, and 5.5 µJ, corresponding to laser repetition rates of 50 kHz, 300 kHz, and 1.1 MHz, respectively. The field strength and pulse energy of the terahertz pulses, in kilovolts per centimeter and picojoules, are extracted with electro-optic sampling and not the single-pulse detection configuration [22]. For clarity, the data in Fig. 3(a) collected with NIR-pulse energies 20 and 5.5 µJ are multiplied by factors of 3 and 4, respectively. ...
Standard terahertz time-domain spectroscopy uses a relatively slow multidata acquisition process that has hindered the technique’s ability to resolve “fast” dynamics occurring on the microsecond timescale. This timescale, inaccessible to most ultrafast pump-probe techniques, hosts a range of phenomena that has been left unexplored due to a lack of proper real-time monitoring techniques. In this work, chirped-pulse spectral encoding, a photonic time-stretch technique, and high-speed electronics are used to demonstrate time-resolved terahertz detection at a rate up to 1.1 MHz. This configuration relies on a tabletop optical source and a setup able to resolve every terahertz transient generated by the same source. We investigate the performance of this single-pulse terahertz detection system at different acquisition rates in terms of experimental noise, dynamic range, and signal-to-noise ratio. Our results pave the way towards single-pulse terahertz time-domain spectroscopy at arbitrarily fast rates to monitor complex dynamics in real time.
... The ZnTe and GaSe crystals are representatively used [93,94]. Efforts have been made to increase the pulse energy by using a large aperture (110) ZnTe crystal [91], achieving pulse energies of up to a few μJ [95]. Fig. 9 displays the schematic diagram of the setup built using a ZnTe crystal. ...
... where P(t) is the time-resolved THz power, ε(t) is the normalized THz field transient, ε peak is the THz peak field measured from a reference EOS trace [31], K auto = 1.66 is the correction factor to account for the finite width of the gating pulse calculated based on the autocorrelation function [32], and r THz = 220 µm (1/e 2 ) is the measured THz beam radius using the knife edge method. The spatial chirp of the THz beam at focus was negligible. ...
We combine parametric frequency upconversion with the single-photon counting technology to achieve terahertz (THz) detection sensitivity down to the zeptojoule (zJ) pulse energy level. Our detection scheme employs a near-infrared ultrafast source, a GaP nonlinear crystal, optical filters, and a single-photon avalanche diode. This configuration is able to resolve 1.4 zJ (1.4 × 10–21 J) THz pulse energy, corresponding to 1.5 photons per pulse, when the signal is averaged within only 1 s (or 50,000 pulses). A single THz pulse can also be detected when its energy is above 1185 zJ. These numbers correspond to the noise-equivalent power and THz-to-NIR photon detection efficiency of 1.3 × 10–16 W/Hz1/2 and 5.8 × 10–2%, respectively. To test our scheme, we perform spectroscopy of the water vapor between 1 and 3.7 THz and obtain results that are in agreement with those acquired with a standard electro-optic sampling (EOS) method. Our technique provides a 0.2 THz spectral resolution offering a fast alternative to EOS THz detection for monitoring specific spectral components in spectroscopy, imaging, and communication applications.
... The efficiency of THz wave generation through OR is linked to some factors, like the nonlinear optical coefficient, absorption coefficient, and phase matching their superior properties not only enable them to play a key role in the terahertz field, but also provide a solid foundation for nonlinear research and applications. However, due to the influence of the lattice vibration mode, inorganic crystals are limited when generating wavelength above 10 THz [11][12][13][14]. In contrast, organic crystals exhibit noteworthy second-order nonlinear coefficients, higher electro-optic (EO) coefficients, and lower dielectric constants. ...
In recent years, the application of terahertz technology has gained substantial recognition across various domains. Nonlinear optical crystals have garnered emerged as a focal point of attention due to their pivotal role in advancing this technology. Within the realm of these crystals, organic second-order nonlinear optical materials stand out for their remarkable attributes. Their large nonlinear coefficient, elevated electro-optical coefficient, and low dielectric constant position them as exceptional materials for terahertz radiation sources. This article delves into a comprehensive exploration of two distinct categories of crystals: ionic and molecular. It provides an insightful overview of the structural design strategies employed in these crystals. Furthermore, this paper conducts a thorough analysis of the shared and different properties between these diverse crystal types, including optical, thermal, mechanical and nonlinear aspects. This in-depth exploration paves the way for a better understanding of the potential applications of these crystals in the ever-expanding realm of terahertz technology.
... Here, the expectation value hÁ Á Ái pert is evaluated using the perturbed state (2). As a final remark on these spectroscopic techniques, we note that the sequence of pulses described above has already been implemented in experiments investigating ultrafast magnetization dynamics of materials with spontaneous spin ordering [30][31][32][33], enabled by recent developments in the generation of high-intensity THz-domain pulses with short time resolution [39,40]. Having defined and motivated the study of χ PP , we now move on to investigating its behavior in two-dimensional topologically ordered systems. ...
We show that the presence of anyons in the excitation spectrum of a two-dimensional system can be inferred from nonlinear spectroscopic quantities. In particular, we consider pump-probe spectroscopy, where a sample is irradiated by two light pulses with an adjustable time delay between them. The relevant response coefficient exhibits a universal form that originates from the statistical phase acquired when anyons created by the first pulse braid around those created by the second. This behavior is shown to be qualitatively unchanged by nonuniversal physics including nonstatistical interactions and small nonzero temperatures. In magnetic systems, the signal of interest can be measured using currently available terahertz-domain probes, highlighting the potential usefulness of nonlinear spectroscopic techniques in the search for quantum spin liquids.
... THz electric field strength E THz [kV/cm] has to be measured or estimated in order to compare data between different experiments using a similar electro-optical (EO) sampling method. Two A and B channels of a balanced EO detector define the phase shift ∆φ induced by the peak electric field E THz of THz pulse in ZnTe 110 crystal for the λ = 800 nm laser pulse [50,51]: ...
The generation of circularly polarised single-cycle THz emission with tightly focused femtosecond pulses in air is explained.
... THz electric field strength E THz [kV/cm] has to be measured or estimated in order to compare data between different experiments using a similar electro-optical (EO) sampling method. Two A and B channels of a balanced EO detector define the phase shift ∆φ induced by the peak electric field E THz of THz pulse in ZnTe 110 crystal for the λ = 800 nm laser pulse [50,51]: ...
Two pre-pulses focused at different positions and at different time moments were used to enhance THz emission generated by the main pulse. The emission of THz radiation from air breakdown regions of focused ultrashort fs-laser pulses (800 nm/35 fs) at shockwave front prepared by pre-pulses was investigated, and a 3D spatio-temporal control was established for the most intense emission. The laser pulse-induced air breakdown forms a ~120 micrometers-long focal volume and generates a shockwave that delivers denser air into the focal region of the main pulse for enhanced generation of THz radiation at 0.1-2.5 THz spectral window. The intensity of pre- and main-pulses was at the tunneling ionisation intensities (1-3)x1016 W/cm2 and corresponded to sub-critical (transparent) plasma in air. Polarisation analysis revealed that the orientation of the air density gradients generated by pre-pulses and their time-space placement defined the ellipticity of the generated THz electrical field. The rotational electric current is the origin of THz radiation. The current is created by non-parallel gradients of electron density and temperature. Scaling dependencies of THz emission control are established.
... These THz pulses (regardless of their energy) are generated by photoconductive antennas 15 , by laser-induced plasma 16 , in spintronic structures 17 , and by optical rectification in nonlinear crystals [18][19][20][21][22] , all of them driven by ultrashort laser pulses. Photoconductive antennas, mostly used in TDTS devices, generate single-cycle pulses with a spectral bandwidth of 4-6 THz, with pulse energies in the sub-pJ range 15 . ...
... In case of ZnTe and GaP semiconductors, collinearly phase-matched OR is realized when they are pumped at Ti:s 20 and Yb lasers [27][28][29][30] , respectively. However, since their bandgap are relatively low, the significant 2-photon (in case of ZnTe) and 3-photon absorption (2PA, 3PA) at these wavelengths reduces the available conversion efficiency to around 0.02% 27,29,30 due to the generation of free carriers which increases the THz absorption 28 . ...
... Organic crystals are usually characterized by a THz frequency-and pump wavelength-dependent generation length which serves as figure of merit and is defined as follows 24 : where α THz ; α opt represent the absorptions in the THz and optical regime, and l c is the coherence length. To explore the potential impact of pulse front tilting, we should substitute n g = cosðγÞ instead of the group refractive index of the material n gr p in the formula of coherence length (20). An insightful calculation involving a 0.5 mm thick DAST crystal pumped by 2.06 μm wavelength (the wavelength of a thulium-doped laser, or close to a holmium laser, which is much more widespread than a chrome forsterite laser with~1.3 ...
Optical rectification of femtosecond laser pulses has emerged as the dominant technique for generating single- and few-cycle terahertz (THz) pulses. The advent of the tilted pulse front pumping (TPFP) velocity matching technique, proposed and implemented two decades ago, has ushered in significant advancements of these THz sources, which are pivotal in the realm of THz pump-probe and material control experiments, which need THz pulses with microjoule energies and several hundred kV/cm electric field strengths. Furthermore, these THz sources are poised to play a crucial role in the realization of THz-driven particle accelerators, necessitating millijoule-level pulses with tens of MV/cm electric field strengths. TPFP has enabled the efficient velocity matching in lithium niobate crystals renowned for their extraordinary high nonlinear coefficient. Moreover, its adaptation to semiconductor THz sources has resulted in a two-hundred-times enhancement in conversion efficiency. In this comprehensive review, we present the seminal achievements of the past two decades. We expound on the conventional TPFP setup, delineate its scaling limits, and elucidate the novel generation TPFP configurations proposed to surmount these constraints, accompanied by their preliminary outcomes. Additionally, we provide an in-depth analysis of the THz absorption, refractive index, and nonlinear coefficient spectra of lithium niobate and widely used semiconductors employed as THz generators, which dictate their suitability as THz sources. We underscore the far-reaching advantages of tilted pulse front pumping, not only for LN and semiconductor-based THz sources but also for selected organic crystal-based sources and Yb-laser-pumped GaP sources, previously regarded as velocity-matched in the literature.
... Using the same experimental setup, we also measured the terahertz radiation from ZnTe, which is a second-order nonlinear optical crystal without inversion symmetry and widely used to generate terahertz electromagnetic waves via the OR process described by P 0 57 . In general, the third-order nonlinear optical effect described by ...
Nearly monocyclic terahertz waves are used for investigating elementary excitations and for controlling electronic states in solids. They are usually generated via second-order optical nonlinearity by injecting a femtosecond laser pulse into a nonlinear optical crystal. In this framework, however, it is difficult to control phase and frequency of terahertz waves. Here, we show that in a one-dimensional Mott insulator of a nickel-bromine chain compound a terahertz wave is generated with high efficiency via strong electron modulations due to quantum interference between odd-parity and even-parity excitons produced by two-color femtosecond pulses. Using this method, one can control all of the phase, frequency, and amplitude of terahertz waves by adjusting the creation-time difference of two excitons with attosecond accuracy. This approach enables to evaluate the phase-relaxation time of excitons under strong electron correlations in Mott insulators. Moreover, phase- and frequency-controlled terahertz pulses are beneficial for coherent electronic-state controls with nearly monocyclic terahertz waves.
... It leads to the pulse depletion and photogeneration of free carriers that absorb terahertz radiation behind the laser pulse. In particular, these processes are considered as the main limiting factor for the efficiency of collinear terahertz generation in a ZnTe crystal pumped by a Ti:sapphire laser (800 nm wavelength) [8][9][10]. They also lead to a shift in the generated spectrum toward lower frequencies [11]. ...
We found experimentally that Cherenkov-type terahertz radiation produced by optical rectification of ultrashort laser pulses in LiNbO3 can experience strong spectral broadening in the regime of multiphoton laser absorption. The broadening is attributed to the terahertz emission from a surge current of the optically generated carriers. The effect can be used to improve the bandwidth of optical-to-terahertz converters based on optical rectification.
