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Journal ArticleDOI

Terahertz optical rectification from a nonlinear organic crystal

28 Dec 1992-Applied Physics Letters (American Institute of Physics)-Vol. 61, Iss: 26, pp 3080-3082
TL;DR: In this article, optical rectification and subsequent generation of sub-picosecond sub-millimeter-wave radiation from a nonlinear organic crystalline salt was reported, and the magnitude of the rectified field from the organic salt dimethyl amino 4-N-methylstilbazolium tosylate is one and two orders of magnitude larger than that from GaAs and LiTaO3, respectively.
Abstract: We report optical rectification and subsequent generation of subpicosecond submillimeter‐wave radiation from a nonlinear organic crystalline salt. With optical excitation at a wavelength of 820 nm and a 150 fs pulse duration, the magnitude of the rectified field from the organic salt dimethyl amino 4‐N‐methylstilbazolium tosylate is one and two orders of magnitude larger than that from GaAs and LiTaO3 crystals, respectively. This organic crystal presently provides the most intense terahertz radiated field among all of the natural nonexternally biased materials we know.
Citations
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Journal ArticleDOI
TL;DR: Terahertz spectroscopy and imaging provide a powerful tool for the characterization of a broad range of materials, including semiconductors and biomolecules, as well as novel, higher-power terahertz sources.
Abstract: Terahertz spectroscopy systems use far-infrared radiation to extract molecular spectral information in an otherwise inaccessible portion of the electromagnetic spectrum. Materials research is an essential component of modern terahertz systems: novel, higher-power terahertz sources rely heavily on new materials such as quantum cascade structures. At the same time, terahertz spectroscopy and imaging provide a powerful tool for the characterization of a broad range of materials, including semiconductors and biomolecules.

2,673 citations

Journal ArticleDOI
TL;DR: In this paper, a combined theoretical and experimental investigation of the generation of few-cycle terahertz (THz) pulses via the nonlinear effect of optical rectification and of their coherent detection via electro-optic sampling is presented.
Abstract: We present a combined theoretical and experimental investigation of the generation of few-cycle terahertz (THz) pulses via the nonlinear effect of optical rectification and of their coherent detection via electro-optic sampling. The effects of dispersive velocity matching, absorption of the optical and the THz waves, crystal thickness, pulse diameter, pump pulse duration, and two-photon absorption are discussed. The theoretical calculations are compared with the measured spectra of THz pulses that have been generated and detected in crystals of the highly nonlinear organic salt 4-N,N-dimethylamino-4′-N′-methyl stilbazolium tosylate (DAST). The results are found to be in agreement with the theory. By the selection of the optical pump wavelength between 700 and 1600 nm, we achieved several maxima of the overall generation and detection efficiency in the spectral range between 0.4 and 6.7 THz, with an optimum at 2 THz generated with 1500 nm laser pulses.

378 citations

Journal ArticleDOI
TL;DR: Investigations relating to the potential of terahertz imaging and spectroscopy for cancer diagnosis will be highlighted and a short review of recent advances is provided.
Abstract: The terahertz region lies between the microwave and infrared regions of the electromagnetic spectrum such that it is strongly attenuated by water and very sensitive to water content. Terahertz radiation has very low photon energy and thus it does not pose any ionization hazard for biological tissues. Because of these characteristic properties, there has been an increasing interest in terahertz imaging and spectroscopy for biological applications within the last few years and more and more terahertz spectra are being reported, including spectroscopic studies of cancer. The presence of cancer often causes increased blood supply to affected tissues and a local increase in tissue water content may be observed: this acts as a natural contrast mechanism for terahertz imaging of cancer. Furthermore the structural changes that occur in affected tissues have also been shown to contribute to terahertz image contrast. This paper introduces terahertz technology and provides a short review of recent advances in terahertz imaging and spectroscopy techniques. In particular investigations relating to the potential of terahertz imaging and spectroscopy for cancer diagnosis will be highlighted.

312 citations

Journal ArticleDOI
TL;DR: The development of THz PCA technology through the last 30 years is reviewed, the key modalities of improving device performance are identified, and literature is reviewed to summarize the progress made in these areas.
Abstract: Photoconductive antennas (PCAs) have been extensively utilized for the generation and detection of both pulsed broadband and single frequency continuous wave terahertz (THz) band radiation. These devices form the basis of many THz imaging and spectroscopy systems, which have demonstrated promising applications in various industries and research fields. The development of THz PCA technology through the last 30 years is reviewed. The key modalities of improving device performance are identified, and literature is reviewed to summarize the progress made in these areas. The goal of this review is to provide a collection of all relevant literature to bring researchers up to date on the current state and remaining challenges of THz PCA technology.

264 citations

Journal ArticleDOI
TL;DR: In this paper, the authors review the recent progress in the development of photonic applications based on the organic crystal 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST).
Abstract: We review the recent progress in the development of photonic applications based on the organic crystal 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST). DAST is an organic salt with an extremely high nonlinear optical susceptibility chi(2)(-2omega,omega,omega)=580plusmn30 pm/V at 1.54 mum, a high electrooptic figure of merit n 3 r = 455plusmn80 pm/V at 1.54 mum, as well as a low dielectric constant epsiv = 5.2 . DAST is, therefore, very attractive for high-speed optical modulators and field detectors, as well as for frequency conversion and the generation of terahertz waves. Several techniques to microscopically structure this material have been developed recently; including modified photolithography, photobleaching, femtosecond laser ablation, graphoepitaxial growth, ion implantation, and direct electron-beam structuring, which open new perspectives of using this exceptional material for high-speed very-large-scale integrated photonics.

236 citations

References
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Journal ArticleDOI
TL;DR: In this article, the generation transmission and detection of extremely rapid electromagnetic pulses have been achieved using fast photoconducting materials as time-varying Hertzian dipoles, which overcomes many of the limitations imposed by transmission line structures, and due to its jitter free behavior and open geometry is ideally suited for transient electromagnetic measurements of materials.
Abstract: The generation transmission, and detection of extremely rapid electromagnetic pulses have been achieved using fast photoconducting materials as time‐varying Hertzian dipoles. This approach, which has a measured time response of 1.6 ps, overcomes many of the limitations imposed by transmission line structures, and due to its jitter‐free behavior and open geometry is ideally suited for transient electromagnetic measurements of materials.

992 citations

Journal ArticleDOI
02 Aug 1989-Science
TL;DR: A series of organic salts, in which the cation has been designed to have a large molecular hyperpolarizability, has been prepared as discussed by the authors, which leads to materials with large powder second harmonic generation efficiencies, the highest of which is roughly 1000 times that of a urea reference.
Abstract: A series of organic salts, in which the cation has been designed to have a large molecular hyperpolarizability, has been prepared. Variation of the counterion (anion) in many cases leads to materials with large powder second harmonic generation efficiencies, the highest of which is roughly 1000 times that of a urea reference.

620 citations

Journal ArticleDOI
TL;DR: In this paper, a bare semiconductor wafer was illuminated by femtosecond optical pulses, and electromagnetic waves radiated from the surface and formed collinear diffraction-limited electromagnetic beams in the inward and outward directions.
Abstract: We have generated electromagnetic beams from a variety of semiconductors. When a bare semiconductor wafer was illuminated by femtosecond optical pulses, electromagnetic waves radiate from the surface and form collinear diffraction‐limited electromagnetic beams in the inward and outward directions. The amplitude and phase of the radiated field depend on carrier mobility, the strength and polarity of the static internal field at the semiconductor surface.

457 citations

Journal ArticleDOI
TL;DR: In this article, femtosecond optical pulses were used to generate broad bandwidth terahertz radiation from the surfaces of electrooptic materials under the phase mismatched condition.
Abstract: We have observed subpicosecond pulses having terahertz bandwidths generated from electro‐optic materials by using femtosecond optical pulses. The time‐resolved radiation signal clearly indicates that the terahertz radiation comes from the regions within the coherence length near the surfaces of electro‐optic materials under the phase‐mismatched condition. When the high‐energy femtosecond laser pulses are used, this method provides a new way to generate large amplitude broad bandwidth terahertz radiation efficiently.

267 citations