42 research outputs found
Femtosecond dynamics of the optical Stark effect in semiconductor-doped glass
We report the observation of the optical Stark shift in CdSxSe1-x semiconductor-doped glass excited under nonresonant below gap condition and probed with femtosecond optical pulses. An ultrafast and pure light-induced shift of the bandedge is observed. The measured dependence of the band edge shift with the pump pulse peak intensity is linear for pump intensities up to 0.3 GW/cm(2) Above this value, departure from linearity is observed. For a pump intensity of 3 GW/cm(2), the band shifts by 11 meV. The response of the shift tracks the profile of the pumping pulse. (C) 1996 American Institute of Physics.6881093109
MODEL CALCULATION OF THE FEMTOSECOND CARRIER DYNAMICS IN AL0.48GA0.52AS
We present a model calculation capable of investigating the dynamics of photoexcited carriers in the Al0.48Ga0.52As indirect gap semiconductor. Nearly resonant excitation at the Gamma point produces low excess energy carriers, so that we use Boltzmann like equations and assume thermalized carrier distributions for each of the conduction valleys. Some aspects of the carrier dynamics are discussed and pump and probe measurements are compared to the calculated saturation bleaching, evidencing a very good agreement between theory and experiment. We obtain a value of 3.5 eV/Angstrom A for the D-Gamma X deformation potential.7663749375
SPECTRAL NARROWING IN THE PROPAGATION OF CHIRPED PULSES IN SINGLE-MODE FIBERS
A theoretical study of the nonlinear propagation of picosecond chirped pulses in single-mode fibers is presented. We show that, under appropriate conditions, spectral narrowing-rather than broadening, as is generally believed-is induced, owing to the interplay of self-phase-modulation and dispersion. For downchirped pulses at a wavelength of 0.9 mum and a peak power as low as 0.1 W, substantial spectral narrowing occurs.18969970
POSITIVE AND NEGATIVE CHIRPING OF LASER-PULSES SHORTER THAN 100 FSEC IN A SATURABLE ABSORBER
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Size effects on the phonon spectra of quantum dots in CdTe-doped glasses
We studied the confinement effects on the phonon Spectra of CdTe quantum dots by means of resonant Raman scattering measurements. The spectra show clearly longitudinal optical phonons, surface phonons and some of their overtone combinations. We show that the scattering due to surface phonons increases as the quantum dot size decreases. The results are obtained by tuning the laser excitation energy to resonance for quantum dots of different sizes inside the broad size distribution in CdTe-doped glasses. (C) 1996 American Institute of Physics.69335735
GENERATION OF TUNABLE FEMTOSECOND PULSES IN THE 690-750 NM WAVELENGTH REGION
We report the generation of intense wavelength tunable pulses between 690 and 750 nm. of 65-85 fs duration and energies per pulse 1-2-mu-J, via continuum amplification at 8.5 kHz. These pulses are compressed to durations of 12-13 fs.861656