Kinetics and wavelength dependence of thermal and excited-state population on lens effect induced in a Nd:YAG rod amplifier.

Using a wavefront sensor, we have measured the temporal evolution of the lens induced in a Nd:YAG rod amplifier under side pumping by laser diode bars centered around 808 nm in a quasi-continuous wave regime. The evolution of the induced lens is drastically different when measured with a probe pulse centered at 532 nm or 1064.5 nm.

Optical damage limit of efficient spintronic THz emitters.

THz pulses are generated from femtosecond pulse-excited ferromagnetic/nonmagnetic spintronic heterostructures via inverse spin Hall effect. The highest possible THz signal strength from spintronic THz emitters is limited by the optical damage threshold of the corresponding heterostructures at the excitation wavelength. For the thickness-optimized spintronic heterostructure, the THz generation efficiency does not saturate with the excitation fluence even up till the damage threshold.

Enhancement in optically induced ultrafast THz response of MoSeMoS heterobilayer.

THz conductivity of large area MoS and MoSe monolayers as well as their vertical heterostructure, MoSeMoS is measured in the 0.3-5 THz frequency range. Compared to the monolayers, the ultrafast THz reflectivity of the MoSeMoS heterobilayer is enhanced many folds when optically excited above the direct band gap energies of the constituting monolayers.

Conical versus Gaussian terahertz emission from two-color laser-induced air plasma filaments.

In this Letter, we demonstrate that the far-field terahertz (THz) beam generated from a Ti:Sapphire two-color laser-induced filament can exhibit a conical or Gaussian distribution, depending on the filtering experimental conditions. Using both an incoherent Golay cell detector and a two-dimensional coherent electro-optic detection covering the 0.2-2.

Study of the Photoswitching of a Fe(II) Chiral Complex through Linear and Nonlinear Ultrafast Spectroscopy.

Photoswitching the physical properties of molecular systems opens large possibilities for driving materials far from equilibrium toward new states. Moreover, ultrashort pulses of light make it possible to induce and to record photoswitching on a very short time scale, opening the way to fascinating new functionalities. Among molecular materials, Fe(II) complexes exhibit an ultrafast spin-state transition during which the spin state of the complex switches from a low spin state (LS, = 0) to a high spin state (HS, = 2).

Three-dimensional terahertz computed tomography of human bones.

Three-dimensional terahertz computed tomography has been used to investigate dried human bones such as a lumbar vertebra, a coxal bone, and a skull, with a direct comparison with standard radiography. In spite of lower spatial resolution compared with x-ray, terahertz imaging clearly discerns a compact bone from a spongy one, with strong terahertz absorption as shown by additional terahertz time-domain transmission spectroscopy.

Ultrafast dynamics of metal complexes of tetrasulphonated phthalocyanines.

A promising material in medicine, electronics, optoelectronics, electrochemistry, catalysis, and photophysics, tetrasulphonated aluminum phthalocyanine (AlPcS(4)), is investigated by means of steady-state and time-resolved pump-probe spectroscopies. Absorption and steady-state fluorescence spectroscopy indicate that AlPcS(4) is essentially monomeric. Spectrally resolved pump-probe data are recorded on time scales ranging from femtoseconds to nanoseconds.

Tuning and focusing THz pulses by shaping the pump laser beam profile in a nonlinear crystal.

Spatially shaped femtosecond laser pulses are used to generate and to focus tunable terahertz (THz) pulses by Optical Rectification in a Zinc Telluride (ZnTe) crystal. It is shown analytically and experimentally that the focusing position and spectrum of the emitted THz pulse can be changed, in the intermediate field zone, by controlling the spatial shape of the near-infrared (NIR) femtosecond (fs) laser pump. In particular, if the pump consists of concentric circles, the emitted THz radiation is confined around the propagation axis, producing a THz pulse train, and focusing position and spectrum can be controlled by changing the number of circles and their diameter.