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Dive into the research topics where A. Peremans is active.

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Featured researches published by A. Peremans.


Applied Physics Letters | 2001

Pumping picosecond optical parametric oscillators by a pulsed Nd:YAG laser mode locked using a nonlinear mirror

Alaa Adin Mani; Laurent Dreesen; Ph. Hollander; Christophe Humbert; Yves Caudano; P.A. Thiry; A. Peremans

We report on the performances of the mode locking of a flash-lamp-pumped Nd:YAG laser using a frequency-doubling nonlinear mirror combined with a two-photon absorber. Pulse lengths from 12 to 8 ps are generated. We show that the flat shape of the pulse-train envelope generated by the oscillator is adapted for the synchronous pumping of optical parametric oscillators and we demonstrate the efficient generation of an infrared beam tunable from 3800 to 1100 cm−1 with bandwidth of 2 cm−1 in one single conversion stage in LiNbO3 or AgGaS2. The “all-solid-state” laser system enables surface sum-frequency generation spectroscopy to be performed with high sensitivity and high resolution.


Chemical Physics Letters | 2001

Study of the water/poly(ethylene glycol) interface by IR-visible sum-frequency generation spectroscopy

Laurent Dreesen; Christophe Humbert; Philippe Hollander; A. A. Mani; K. Ataka; P.A. Thiry; A. Peremans

We used infrared-visible sum-frequency generation spectroscopy to investigate the vibrational properties of the water/poly(ethylene glycol) interface in the 2800–3800 cm−1 spectral range. The vibrational fingerprint of the interface differs significantly from the one associated with the air/poly(ethylene glycol) interface. It is shown that the poly(ethylene glycol) molecular arrangement, originally relatively well-ordered, becomes disorganised in the presence of water. Moreover, a new OH band is identified demonstrating the strong interaction of water with the polymer.


Chemical Physics Letters | 1997

Vibrational spectroscopy of a Au(hkl)-electrolyte interface by in situ visible-infrared difference frequency generation

A. Le Rille; A. Tadjeddine; W.Q. Zheng; A. Peremans

Abstract We demonstrate a significant decrease in the non-resonant response of gold substrates in IR-VIS nonlinear optical spectroscopy by switching from sum- to difference-frequency generation. This has allowed DFG spectroscopy to show the significant effect of the surface orientation on the adsorption strength of CN − , which decreases from (110) to (100) and (111). Both the linewidth and the potential tuning rate of the DFG resonances are independent of the electrode structure, pointing to CN − being tightly and linearly bound to each nearest surface gold atom.


Surface Science | 2002

Development of a two-color picosecond optical parametric oscillator, pumped by a Nd:YAG laser mode locked using a nonlinear mirror, for doubly-resonant sum frequency generation spectroscopy

A. A. Mani; Laurent Dreesen; Christophe Humbert; Philippe Hollander; Yves Caudano; P.A. Thiry; A. Peremans

Abstract We set up a doubly-resonant sum frequency generation (DR-SFG) spectrometer based on the use of an all-solid-state flash-lamp-pumped Nd:YAG laser that synchronously pumps two parametric oscillators. Pulses as short as 12 ps FWHM are generated by mode locking a Nd:YAG oscillator using a frequency doubling nonlinear mirror combined with a two-photon absorber. The available pump power is shared between a LiNbO 3 /AgGaS 2 optical parametric oscillator (OPO), tunable from 3800 to 1100 cm −1 and a BBO OPO tunable from 410 to 2600 nm. Spectral resolution and pulse are 2 and 3 cm −1 in the infrared and visible spectral ranges, respectively. First DR-SFG spectra of self-assembled monolayers on Au are presented.


Physica Status Solidi (a) | 1999

Sum and Difference Frequency Generation at the Electrochemical Interface

A. Tadjeddine; A. Le Rille; Olivier Pluchery; Franck Vidal; W.Q Zheng; A. Peremans

The surface electronic properties and the vibrational spectroscopy of the electrochemical interface are investigated by in situ Infrared-Visible Sum (SFG) and Difference (DFG) Frequency Generation. We first present the theoretical background of SFG/DFG and their generation at the interface and calculate the interface second-order susceptibility including the resonant contribution of the adsorbate and the non resonant contribution of the metal substrate electronic intraband and interband transitions. The effect of the latter is addressed by comparing the experimental SFG and DFG spectra recorded on silver, platinum and gold substrates. The experimental set-up and procedure are then described, and some selected experimental examples are shown and discussed.


ChemPhysChem | 2010

Orientational analysis of dodecanethiol and p-nitrothiophenol SAMs on metals with polarisation-dependent SFG spectroscopy.

Francesca Cecchet; Dan Lis; Julien Guthmuller; Benoît Champagne; Yves Caudano; Christophe Silien; Alaa Addin Mani; P.A. Thiry; A. Peremans

Polarisation-dependent sum frequency generation (SFG) spectroscopy is used to investigate the orientation of molecules on metallic surfaces. In particular, self-assembled monolayers (SAMs) of dodecanethiol (DDT) and of p-nitrothiophenol (p-NTP), grown on Pt and on Au, have been chosen as models to highlight the ability of combining ppp and ssp polarisations sets (representing the polarisation of the involved beams in the conventional order of SFG, Vis and IR beam) to infer orientational information at metallic interfaces. Indeed, using only the ppp set of data, as it is usually done for metallic surfaces, is not sufficient to determine the full molecular orientation. We show here that simply combining ppp and ssp polarisations enables both the tilt and rotation angles of methyl groups in DDT SAMs to be determined. Moreover, for p-NTP, while the SFG active vibrations detected with the ppp polarisation alone provide no orientational information, however, the combination with ssp spectra enables to retrieve the tilt angle of the p-NTP 1,4 axis. Though orientational information obtained by polarisation-dependent measurements has been extensively used at insulating interfaces, we report here their first application to metallic surfaces.


Applied Physics Letters | 1999

All-solid-state 12 ps actively passively mode-locked pulsed Nd:YAG laser using a nonlinear mirror

Alaa Adin Mani; Ph. Hollander; P.A. Thiry; A. Peremans

Efficient mode locking of a flash-lamp-pumped Nd:YAG laser at 1.064 μm is achieved by combining the passive–positive feedback of a frequency doubling nonlinear mirror (FDNLM) and the passive–negative feedback of a GaAs platelet. the FDNLM consists of a BBO crystal and of a dichroic mirror. Pulse durations as short as 12 ps are obtained. Temporal evolution of pulse duration in the pulse train is presented and discussed.


Optics Letters | 2009

Noncritical singly resonant synchronously pumped OPO for generation of picosecond pulses in the mid-infrared near 6.4 μm

A. Peremans; Dan Lis; Francesca Cecchet; Peter G. Schunemann; Kevin T. Zawilski; Valentin Petrov

The recently developed chalcopyrite CdSiP(2) is employed in a picosecond, 90 degrees -phase-matched, synchronously pumped, optical parametric oscillator pumped at 1064 nm to produce steady-state idler pulses near 6.4 microm with an energy as high as 2.8 microJ at 100 MHz, in a train of 2-micros-long macropulses following at a repetition rate of 25 Hz. Without an intracavity etalon, the 12.6-ps-long micropulses have a spectral width of 240 GHz.


ChemPhysChem | 2009

Theoretical simulation of vibrational sum-frequency generation spectra from density functional theory: application to p-nitrothiophenol and 2,4-dinitroaniline.

Julien Guthmuller; Francesca Cecchet; Dan Lis; Yves Caudano; Alaa Addin Mani; P.A. Thiry; A. Peremans; Benoît Champagne

The molecular orientation of adsorbed molecules forming self-assembled monolayers can be determined by combining vibrational sum-frequency generation (SFG) measurements with quantum chemical calculations. Herein, we present a theoretical methodology used to simulate the SFG spectra for different combinations of polarizations. These simulations are based on calculations of the IR vectors and Raman tensors, which are obtained from density functional theory computations. The dependency of the SFG vibrational signature with respect to the molecular orientation is presented for the molecules p-nitrothiophenol and 2,4-dinitroaniline. It is found that a suitable choice of basis set as well as of exchange-correlation (XC) functional is mandatory to correctly simulate the SFG intensities and consequently provide an accurate estimation of the adsorbed molecule orientation. Comparison with experimental data shows that calculations performed at the B3LYP/6-311++G(d,p) level of approximation provide good agreement with experimental frequencies, and with IR and Raman intensities. In particular, it is demonstrated that polarization and diffuse functions are compulsory for reproducing the IR and Raman spectra, and consequently vibrational SFG spectra, of systems such as p-nitrothiophenol. Moreover, the investigated XC functionals reveal their influence on the relative intensities, which show rather systematic variations with the amount of Hartree-Fock exchange. Finally, further aspects of the modeling are revealed by considering the frequency dependence of the Raman tensors.


Journal of the Chemical Society, Faraday Transactions | 1996

Investigation of the vibrational properties of CN– on a Pt electrode by in situ VIS–IR sum frequency generation and functional density calculations

A. Tadjeddine; A. Peremans; Alain Le Rille; W.Q Zheng; M. Tadjeddine; Jean-Pierre Flament

The vibrational properties of CN– pseudohalide ions adsorbed on a Pt(110) single-crystal electrode in aqueous neutral solution are studied using in situ VIS–IR sum frequency generation (SFG) and compared to theoretical results obtained from density functional theory (DFT) calculations on PtNC– and PtCN– molecular ions. As observed previously on a polycrystalline electrode, the adsorption behaviour of both ions depends drastically on the electrode potential and on the immersion potential in a CN–-containing solution. When the electrode is immersed at negative potential, two absorption bands are detected in the spectral range of the CN– stretching vibration modes on a surface site. The first resonance at 2070 cm–1 is already observed at –1.4 V (Ag/AgCl), in the hydrogen evolution potential region, with an initial potential tuning rate of 20 cm–1. A second narrow resonance, peaking at 2150 cm–1, starts growing at –0.6 V (Ag/AgCl). The occurrence of two resonances, corresponding to N-bound and C-bound CN– species, is clearly evidenced for a single-crystal electrode, and appears as a genuine property of the system, not a side effect induced by surface defects. The polycrystalline structure and the defects influence the shape, the position and the width of the resonances, not the basic spectroscopic properties of the system. This result is further supported by new density functional calculations of the vibrational properties of the PtCN– and PtNC– molecular ions.

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A. Tadjeddine

Centre national de la recherche scientifique

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A. A. Mani

University of Limerick

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Dan Lis

Université de Namur

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