Surface plasmon-enhanced terahertz emission from a hemicyanine self-assembled monolayer

Ramakrishnan, Gopakumar; Kumar, N. V. Narendra; Planken, Paul C. M.; Tanaka, Daisuke; Kajikawa, Kotaro

doi:10.1364/oe.20.004067

Cited by 20 publications

(19 citation statements)

References 24 publications

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“…As Ramakrishnan et al recently pointed out [18], the different observed dependencies of the THz fluence on pump power do not necessarily contradict * Corresponding author: dmitry.polyushkin@tuwien.ac.at each other, rather they may be associated with different regimes of THz emission that occur under these different experimental conditions. Experiments for which OR is invoked typically involve relatively low peak-power Ti:sapphire laser pulses (see Refs.…”

Section: Introductionmentioning

confidence: 86%

“…Since then different metallic materials and structures have been used to generate THz radiation: nanostructured silver and gold films [11][12][13], semicontinuous metal films [14,15], and metallic nanoparticles [15,16]. Two distinct mechanisms have been proposed to explain the observed generation of THz radiation: OR on metal surfaces [10,14,[16][17][18] and multiphoton photoelectron emission (MPE) [11,15,19,20]. In the latter case, the THz radiation is produced by the ponderomotive acceleration of the ejected electrons caused by the high electric field gradients that occur in the proximity of metal surfaces [21], owing to plasmonic enhancement [11,15].…”

Section: Introductionmentioning

confidence: 99%

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Mechanisms of THz generation from silver nanoparticle and nanohole arrays illuminated by 100 fs pulses of infrared light

et al. 2014

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We study THz pulses generated from plasmonic metal nanostructures under femtosecond illumination of near-IR light. We find two regimes of excitation, according to the order of the dependence of the THz fluence on the incident near-IR intensity: less then second order at low intensities, changing to approximately fourth order for higher intensities. These regimes are most likely associated with two THz generation mechanisms: optical rectification, and the ponderomotive acceleration of ejected electrons. These data provide evidence that both mechanisms can be at work in the same experiment.

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Section: Introductionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Mechanisms of THz generation from silver nanoparticle and nanohole arrays illuminated by 100 fs pulses of infrared light

et al. 2014

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“…On the other hand, Ramakrishnan and Planken have reported THz emission from a thin percolated gold film of 10 nm thickness, having localized surface plasmon (LSP) hot spots [5]. Recently Ramakrishnan et al observed THz emission from ordered NLO chromophores in a molecular monolayer at the surface plasmon resonance condition [6]. In these studies, the THz emission amplitude is quadratic in the excitation field, suggesting that the THz emission is based on the second-order NLO process.…”

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confidence: 99%

“…Light reflected at the sample was detected by the spectrometer using another bundle optical fiber (0.4 mm in diameter). The THz emission was measured using the optical geometry, described in previous papers [5,6]. As the light source, a Ti:sapphire oscillator (Scientific XL, Femtolasers) was used, generating pulses of 50 fs duration, at a central wavelength of 800 nm at a repetition rate of 11 MHz.…”

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confidence: 99%

Terahertz emission from surface-immobilized gold nanospheres

et al. 2012

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Electromagnetic wave emission based on optical rectification at terahertz (THz) wavelengths was observed from surface-immobilized gold nanospheres (SIGNs) above a gold surface. Although the excitation wavelength is offresonant with the localized surface plasmons, the THz emission field was observed to be approximately 4.8 times greater than that from a percolated gold thin film of 10 nm thickness. A theoretical calculation predicts that the light electric field is enhanced in the SIGN system, even at off-resonance wavelengths. The observed THz field amplitude was quadratic with the illumination light field, suggesting that the THz generation is due to a second-order nonlinear optical process. showed THz generation at gold and silver surfaces [3]. A metallic surface shows second-order NLO activity because of the lack of an inversion center near the surface. Later they reported OR-based THz generation in thick metal films (100-200 nm thick), and attributed the optical nonlinearity to nonlocal effects [4]. On the other hand, Ramakrishnan and Planken have reported THz emission from a thin percolated gold film of 10 nm thickness, having localized surface plasmon (LSP) hot spots [5]. Recently Ramakrishnan et al. observed THz emission from ordered NLO chromophores in a molecular monolayer at the surface plasmon resonance condition [6]. In these studies, the THz emission amplitude is quadratic in the excitation field, suggesting that the THz emission is based on the second-order NLO process. On the contrary, Welsh et al. [7] and Polyushkin et al.[8] observed a non-quadratic dependence of the THz emission amplitude on the incident electric field. They attributed the THz emission from the metallic surface to multiphoton ionization and ponderomotive acceleration of electrons in the evanescent field produced by surface plasmons. This process may be called gindirect OR. These different observations suggest that different THz generation mechanisms are possible at gold surfaces.In this letter, we report THz emission from surfaceimmobilized gold nanospheres (SIGNs) above a gold surface with a gap distance of less than 1 nm. The SIGN structure is schematically illustrated in Fig. 1(a). The gap between the SIGN and the surface is supported by an aminoundecanethiol (AUT) self-assembled monolayer (SAM). The SIGNs show an intense resonance of LSPs, as a result of the EM interaction between the SIGNs and the gold surface [9][10][11][12][13]. Second-order NLO optical phenomena, second-harmonic generation (SHG) [10,11], OR and the Pockels effect [12], have been observed from the SIGNs, since the SIGN structure is noncentrosymmetric. Here, THz emission was observed from the SIGNs and its amplitude was found to be quadratic in the excitation field amplitude. This indicates that the THz generation is due to a second-order NLO process.The SIGN sample was prepared by the following procedure: As a substrate, a 100 nm thick thin gold film was vacuum-evaporated on a glass slide. The surface was covered with an AUT SAM, by dipping the gold subs...

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“…In recent years, terahertz related research and technology development has acquired a significant interest of the scientific community all around the globe. This is because of the various applications that terahertz radiations can advance [1][2][3][4][5].This include high speed communication [6], sub wavelength imaging [7], slow light devices [8], bio sensing [9], spectroscopy etc. The development of the waveguides at terahertz frequencies has been one of the primary focus of research in this fast growing area of science and technology.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of terahertz surface plasmon polaritons propagating in a parallel plate configuration

Kaur

et al. 2016

J. Phys.: Conf. Ser.

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Abstract:In this paper, we present numerical analysis of terahertz (THz) surface plasmon polaritons propagating in a parallel plate configuration. A planar metal surface has the ability to support loosely bound surface waves, called Zenneck waves at terahertz frequencies. Two parallel metal plates separated by a narrow vacuum region can lead to the highly confined terahertz surface plasmon modes at specific frequencies. The frequency of the terahertz mode can be changed with a change in the gap between the plates. Further, we observed that the carrier concentration of plates strongly effect the frequency of the terahertz mode as well as its properties. We have examined in detail the dispersion properties of the terahertz surface plasmons supported by the parallel plate configuration with a varying gap width as well as carrier density of the plates.

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Surface plasmon-enhanced terahertz emission from a hemicyanine self-assembled monolayer

Cited by 20 publications

References 24 publications

Mechanisms of THz generation from silver nanoparticle and nanohole arrays illuminated by 100 fs pulses of infrared light

Mechanisms of THz generation from silver nanoparticle and nanohole arrays illuminated by 100 fs pulses of infrared light

Terahertz emission from surface-immobilized gold nanospheres

Numerical analysis of terahertz surface plasmon polaritons propagating in a parallel plate configuration

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