Relativistically moving dielectric perturbations can be used to manipulate light in new and exciting ways beyond the capabilities of traditional nonlinear optics. Adiabatic interaction with the moving front modulates the wave simultaneously in both space and time, and manifests a front-induced transition in both wave vector and frequency yielding exotic effects including non-reciprocity and time-reversal. Here, we introduce a technique called SLIPSTREAM, Spacetime Light-Induced Photonic STRucturEs for Advanced Manipulation. The technique is based on the creation of relativistic fronts in a semiconductor-filled planar waveguide by photoexcitation of mobile charge carriers. Here we demonstrate the capabilities of SLIPSTREAM for novel manipulation of THz light pulses through relativistic front-induced transitions. In the sub-luminal front velocity regime, we generate temporally stretched THz waveforms, with a quasi-static field lasting for several picoseconds tunable with the front interaction distance. In the super-luminal regime, the carrier front outpaces the THz pulse and a time-reversal operation is performed via a front-induced intra-band transition. We anticipate our platform will be a versatile tool for future applications in the THz spectral band requiring direct and advanced control of light at the sub-cycle level.
A new type of tilted-pulse-front pumped terahertz (THz) source has been demonstrated, which is based on a lithium niobate plane-parallel slab with an echelon structure on its input surface. Single-cycle pulses of 1 microjoule energy and 0.30 THz central frequency have been generated with 0.05% efficiency from such a source. One order-of-magnitude increase in efficiency is expected by pumping a cryogenically cooled echelon of increased size and thickness with a Ti:sapphire laser. The use of a plane-parallel nonlinear optical crystal slab enables straightforward scaling to high THz pulse energie…
This paper discusses numerical and experimental results on frequency downshifting and upshifting of a 10 $μ$m infrared laser to cover the entire wavelength (frequency) range from $λ$=1-150 $μ$m ($ν$=300-2 THz) using two different plasma techniques. The first plasma technique utilizes frequency downshifting of the drive laser pulse in a nonlinear plasma wake. Based on this technique, we have proposed and demonstrated that in a tailored plasma structure multi-millijoule energy, single-cycle, long-wavelength IR (3-20 $μ$m) pulses can be generated by using an 810 nm Ti:sapphire drive laser. Here w…
Cactus-like Metamaterial Structures for Electromagnetically Induced Transparency at THz frequencies
Foundation for Research and Technology-Hellas（希腊研究与技术基金会）；National and Kapodistrian University of Athens（雅典国立卡波季斯特里大学）；National Hellenic Research Foundation（国家希腊研究基金会）；University of Regensburg（雷根斯堡大学）
High-order harmonic generation by femtosecond laser pulse in the presence of a moderately strong terahertz (THz) field is studied under the strong field approximation, showing a simple proportionality of near-cutoff even-order harmonic (NCEH) amplitude to the THz electric field. The formation of the THz induced-NCEHs is analytically shown for both continuous wave and Gaussian pulse. The perturbation analysis with regard to the frequency ratio of the THz field to the femtosecond pulse shows the THz-induced NCEHs originates from its first-order correction, and the available parametric conditions…
The metamaterial analogue of electromagnetically induced transparency (EIT) in terahertz (THz) regime holds fascinating prospects for filling the THz gap in various functional devices. In this paper, we propose a novel hybrid metamaterial to actively manipulate the resonance strength of EIT effect. By integrating a monolayer graphene into a THz metal metamaterial, an on-to-off modulation of the EIT transparency window is achieved under different Fermi levels of graphene. According to the classical two-particle model and the distributions of the electric field and surface charge density, the ph…
Based on the quantum master equation approach, the nonlinear electric conductivity of graphene is investigated under static electric fields for various chemical potential shifts. The simulation results show that, as the field strength increases, the effective conductivity is firstly suppressed, reflecting the depletion of effective carriers due to the large displacement in the Brillouin zone caused by the strong field. Then, as the field strength exceeds $1$~MV/m, the effective conductivity increases, overcoming the carrier depletion via the Landau--Zener tunneling process. Based on the nonlin…
We apply terahertz (THz) near-field streaking in a nanofocusing geometry to investigate plasmon polariton propagation on the shaft of a conical nanotip. By evaluating the delay between a streaking spectrogram for plasmon-induced photoemission with a measurement for direct apex excitation, we obtain an average plasmon group velocity, which is in agreement with numerical simulations. Combining plasmon-induced photoemission with THz near-field streaking facilitates extensive control over localized photoelectron sources for time-resolved imaging and diffraction.
Electromagnetic radiation within the terahertz (THz) frequency range is of great interest for applications in remote sensing and time-domain spectroscopy. The laser-induced plasmas are promising mediums for generating THz radiation. It has been recently reported that focusing femtosecond Bessel pulses inside dielectrics induces a high aspect ratio over-critical plasmas. Here we show that the intense resonantly driven electrostatic fields at the so-called critical surface lead to THz radiation emission. Through three-dimensional particle-in-cell simulation and analytical derivation, we have inv…
The organic terahertz (THz) generation crystal BNA has recently gained traction as a valuable source to produce broadband THz pulses. Even when pumped with 800-nm light, thin BNA crystals can produce relatively high electric fields with frequency components out to 5 THz. However, the THz output when pumped with 800-nm light is limited by the damage threshold of the organic crystal. Here we report that the damage threshold of BNA can be significantly improved by physically bonding BNA to a high-thermal conductivity sapphire window. When pumped with 800-nm light from an amplified Ti:sapphire las…
The intense terahertz (THz) pulses facilitate the observation of various nonlinear optical effects and manipulation of material properties. In this work, we report a convenient approach that can produce strong broadband terahertz pulses with center frequency tunable between 2-4 THz. The coherent THz light source with pulse energy of 1.2 microjoule can be generated from a low-cost crystalline quartz pumped by an ultrashort tilted wave-front pulse. Thanks to the wide transparent spectral window and high damage threshold, our theoretical analysis and experiment show that the optical rectification…
Terahertz field-induced second harmonic generation (TFISH) is a technique for optical detection of broad-band THz fields. We show that by placing an iris at the interaction volume of the THz and optical fields, the TFISH signal increases by few ten-fold in atmospheric air. The iris-assisted TFISH amplification is characterized at varying air pressures and probe intensities and provides an elegant platform for studying nonlinear phase-matching in the gas phase.
Continuous and concerted development of colloidal quantum-dot light-emitting diodes over the past two decades has established them as a bedrock technology for the next generation of displays. However, a fundamental issue that limits the performance of these devices is the quenching of photoluminescence due to excess charges from conductive charge transport layers. Although device designs have leveraged various workarounds, doing so often comes at the cost of limiting efficient charge injection. Here we demonstrate that high-field terahertz (THz) pulses can dramatically brighten quenched QDs on…
A novel mechanism to realize dynamically tunable electromagnetically induced transparency (EIT) analogue in the terahertz (THz) regime is proposed. By putting the electrically controllable monolayer graphene under the dark resonator, the amplitude of the EIT resonance in the metal-based metamaterial can be modulated substantially via altering the Fermi level of graphene. The amplitude modulation can be attributed to the change in the damping rate of the dark mode caused by the recombination effect of the conductive graphene. This work provides an alternative way to achieve tunable slow light e…
We theoretically study the THz-induced high-order harmonic generation (HHG) and nonlinear electric transport in graphene based on the quantum master equation with the relaxation time approximation. To obtain microscopic insight into the phenomena, we compare the results of the fully dynamical calculations with those under a quasi-static approximation, where the electronic system is approximated as a nonequilibrium steady state. As a result, we find that the THz-induced electron dynamics in graphene can be accurately modeled with the nonequilibrium steady-state at each instance. The population …
Mitigating Electrode-Induced Polarization Artifacts in Miniaturized Terahertz Detectors via a Ring-Shaped Electrode Design
State Key Laboratory of Optoelectronic Materials and Technologies（光电功能材料国家重点实验室）；Guangdong Province Key Laboratory of Display Material and Technology（广东省显示材料与技术重点实验室）；School of Electronics and Information Technology, Sun Yat-sen University（中山大学电子与信息工程学院）
Rotation of the plane of the polarization of light in the presence of a magnetic-field, known as the Faraday rotation, is a consequence of the electromagnetic nature of light and has been utilized in many optical devices. Current efforts aim to realize the ultrafast Faraday rotation on a sub-picosecond time scale. Thereby, the Faraday medium should allow an ultrafast process by which in the presence of an ultrashort intense magnetic-field, the light polarization rotates. We meet these criteria by applying an intense single cycle THz magnetic-field to simple molecular liquids and demonstrate th…
Moderate-terahertz-induced plateau expansion of high-order harmonic generation to soft X-ray region
Duy Tan University（越南科技大学）；Van Lang University（文郎大学）；Ton Duc Thang University（胡志明市铁城大学）；Ho Chi Minh City University of Education（胡志明市教育大学）；M. V. Lomonosov Moscow State University（莫斯科国立罗蒙诺索夫大学）
We introduce THz Stark spectroscopy by using intense single-cycle terahertz pulses as the electric field source and monitoring the induced spectral response of an isotropic molecular ensemble with a coincident femtosecond supercontinuum pulse. THz Stark spectroscopy offers several advantages over conventional Stark spectroscopy and opens previously inaccessible perspectives. Most importantly, THz pulses oscillate faster than typical molecular rotations and consequently eliminate the requirement to freeze the samples to prevent poling effects. Hence, THz Stark spectroscopy allows for time-resol…
A THz light amplifier and the corresponding methods are proposed, based on the Raman interaction between a THz light and visible light lasers. Two lasers, with their frequencies differing by that of a Langmuir wave, counter-propagate inside a background plasma, exciting a rather strong Langmuir wave. The THz light amplification occurs through the non-resonant Raman scattering between the THz light and one of the lasers in the presence of the mentioned Langmuir wave. It is normally the case that the non-resonant scattering does not exchange the energy between E \&M fields but the author demonst…
By introducing methyl fluoride (CH$_3$F) as a new gain medium for a quantum cascade laser-pumped molecular laser (QPML), we demonstrate continuous-wave lasing from more than 120 discrete transitions spanning the frequency range 0.25 to 1.3 THz. The unprecedented degree of spectral tuning achieved with CH$_3$F also confirms the universality of the QPML concept: for all polar gas molecules, lasing can be induced on any dipole-allowed rotational transition by sufficient pumping of a related roto-vibrational transition using a continuously tunable quantum cascade laser.
