Terahertz pulse generation in an organic crystal by optical rectification and resonant excitation of molecular charge transfer

Carey, John J.; Bailey, R. T.; Pugh, D.; Sherwood, J. N.; Cruickshank, F. R.; Wynne, Klaas

doi:10.1063/1.1527237

Cited by 70 publications

(50 citation statements)

References 15 publications

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“…OH1 shows a higher spectral density at lower frequency going along with a wider spread of spectral density at least up to 12 THz. The main absorption resonances occur at 1.45 and 2.85 THz (consistent with previous reports 26 ). Here again we could not find reports on higher frequencies resonances, but from our spectrum we anticipate resonances around {4.9, 6.3} THz.…”

Section: Methodssupporting

confidence: 78%

“…As illustrated in Fig. 1d, a bending of the optical pump wavefront leads to a bending of the generated THz wavefront 26 . For a specific frequency and single emitting spot size, there is an optimum value for such a bending that compensates for the natural divergence of the emitted THz beam, thus leading to a collimated THz beam at the input of the focusing system.…”

Section: Resultsmentioning

confidence: 99%

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Demonstration of a low-frequency three-dimensional terahertz bullet with extreme brightness

2015

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The brightness of a light source defines its applicability to nonlinear phenomena in science. Bright low-frequency terahertz (o5 THz) radiation confined to a diffraction-limited spot size is a present hurdle because of the broad bandwidth and long wavelengths associated with terahertz (THz) pulses and because of the lack of THz wavefront correctors. Here using a present-technology system, we employ a wavefront manipulation concept with focusing optimization leading to spatio-temporal confinement of THz energy at its physical limits to the least possible three-dimensional light bullet volume of wavelength-cubic. Our scheme relies on finding the optimum settings of pump wavefront curvature and post generation beam divergence. This leads to a regime of extremely bright PW m À 2 level THz radiation with peak fields up to 8.3 GVm À 1 and 27.7 T surpassing by far any other system. The presented results are foreseen to have a great impact on nonlinear THz applications in different science disciplines.

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Section: Methodssupporting

confidence: 78%

Section: Resultsmentioning

confidence: 99%

Demonstration of a low-frequency three-dimensional terahertz bullet with extreme brightness

2015

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“…10 have been shown to exhibit much higher EO coefficients than their inorganic counterparts and efficiently generate and detect the THz radiation. More encouragingly, amorphous EO polymers exhibit not only high EO coefficients but also the absence of phonon absorption (in the THz regime).…”

Section: Zheng Et Almentioning

confidence: 99%

Organic Broadband TeraHertz Sources and Sensors

Zheng¹,

McLaughlin²,

Cunningham³

et al. 2007

Journal of Nanoelectronics and Optoelectronics

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We review recent research using organic materials for generation and detection of broadband terahertz radiation (0.3 THz−30 THz). The main focus is on amorphous electrooptic (EO) polymers, with semiconducting polymers, molecular salt EO crystals, and molecular solutions briefly discussed. The advantages of amorphous EO polymers over other materials for broadband THz generation (via optical rectification) and detection (via EO sampling) include a lack of phonon absorption (good transparency) in the THz regime, high EO coefficient and good phase-matching properties, and, of course, easy fabrication (low cost). Our ∼12-THz, spectral gap-free THz system based on a polymer emitter-sensor pair is an excellent demonstration of the advantages using of EO polymers. We also present a model that can predict the performance of a polymer-based THz system. Both the dielectric properties of an EO polymer and laser pulse related parameters are included in the model, making the simulations close to real conditions. From our modeling work, the roles the dielectric properties play in the THz generation and detection are clearly seen, providing us with a good guide to select and design suitable EO polymers in the future.

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“…The same property should also give rise to functionally more relevant frequency downconversion ( 30) or optical rectification (26). This phenomenon has been observed in noncentrosymmetric semiconductors (27)(28)(29)(30) and organic crystals (31) in the form of single-cycle radiation in the THz and midinfrared region as a response to ultrashort laser pulses but not in biological materials. On the other hand, long-lasting coherent infrared emission has been observed from heme protein crystals (32), originating solely from the vibrational response of the protein.…”

mentioning

confidence: 99%

Resonant optical rectification in bacteriorhodopsin

Groma

Colonna

Lambry

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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The relative role of retinal isomerization and microscopic polarization in the phototransduction process of bacteriorhodopsin is still an open question. It is known that both processes occur on an ultrafast time scale. The retinal trans3cis photoisomerization takes place on the time scale of a few hundred femtoseconds. On the other hand, it has been proposed that the primary lightinduced event is a sudden polarization of the retinal environment, although there is no direct experimental evidence for femtosecond charge displacements, because photovoltaic techniques cannot be used to detect charge movements faster than picoseconds. Making use of the known high second-order susceptibility (2) of retinal in proteins, we have used a nonlinear technique, interferometric detection of coherent infrared emission, to study macroscopically oriented bacteriorhodopsin-containing purple membranes. We report and characterize impulsive macroscopic polarization of these films by optical rectification of an 11-fs visible light pulse in resonance with the optical transition. This finding provides direct evidence for charge separation as a precursor event for subsequent functional processes. A simple two-level model incorporating the resonant second-order optical properties of retinal, which are known to be a requirement for functioning of bacteriorhodopsin, is used to describe the observations. In addition to the electronic response, long-lived infrared emission at specific frequencies was observed, reflecting charge movements associated with vibrational motions. The simultaneous and phase-sensitive observation of both the electronic and vibrational signals opens the way to study the transduction of the initial polarization into structural dynamics.R etinal proteins play an essential role in a broad range of light-driven biological processes, including vision (1), energy transduction (2), and circadian control (3). All these functions involve both the conversion of light energy into charge separation and retinal isomerization, but the interplay of these processes is the subject of intense debate. The retinal protein of which the initial photochemistry is most extensively studied is the photosynthetic protein bacteriorhodopsin (bR). This protein colors the purple membrane of halobacteria and acts as a light-driven proton pump by means of a multistep process termed the photocycle (2). In the traditional model for the initial transduction step in this cycle is directly light-driven trans3cis isomerization of retinal (4-6); this model has been recently extended by including excited-state skeletal stretching (5, 7). However, experiments with modified bR containing nonisomerizable retinal analogs challenged this model by showing that the initial photo-induced events are not associated with retinal isomerization (8-10). In fact, in an early alternative hypothesis (11), the essential process was proposed to be dielectric relaxation of the protein as a response to sudden polarization upon retinal excitation (11-13). Recent molecular dynamic...

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Terahertz pulse generation in an organic crystal by optical rectification and resonant excitation of molecular charge transfer

Cited by 70 publications

References 15 publications

Demonstration of a low-frequency three-dimensional terahertz bullet with extreme brightness

Demonstration of a low-frequency three-dimensional terahertz bullet with extreme brightness

Organic Broadband TeraHertz Sources and Sensors

Resonant optical rectification in bacteriorhodopsin

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