Showing papers on "Femtosecond published in 1985"
TL;DR: In this article, it was shown that "impulsive" stimulated Raman scattering (ISRS) should occur, with no laser intensity threshold, when a sufficiently short laser pulse passes through many types of matter.
Abstract: It is shown that ‘‘impulsive’’ stimulated Raman scattering (ISRS) should occur, with no laser intensity threshold, when a sufficiently short laser pulse passes through many types of matter. ISRS excitation of coherent optic phonons, molecular vibrations, and other excitations (including rotational, electronic, and spin) may play important roles in femtosecond pulse interactions with molecules, crystals, glasses (including optical fibers), semiconductors, and metals. Spectroscopic applications of ISRS, including time‐resolved spectroscopy of vibrationally distorted molecules and crystals, are discussed.
498 citations
TL;DR: In this article, a transient three-pulse scattering technique for measuring ultrafast dephasing times in condensed matter is analyzed using a perturbative solution of the density matrix equation.
Abstract: A novel transient three-pulse scattering technique for measuring ultrafast dephasing times in condensed matter is analyzed using a perturbative solution of the density matrix equation. The advantages of this technique include subpulsewidth resolution, a clear distinction between homogeneous and inhomogeneous broadening, and sensitivity to spectral cross-relaxation. Its application to the case of a multilevel resonance is also considered. We report results of femtosecond dephasing experiments with dye molecules in liquids and in a polymer host. The dephasing time is determined to be less than 20 fsec for dyes in solution at room temperature. At low temperatures in polymers, a transition from homogeneous to inhomogeneous broadening has been observed and studied as a function of temperature.
242 citations
TL;DR: In this article, a simple imaging technique that can be used to photograph ultrafast processes with time resolution determined by the duration of pump and probe laser pulses is described, showing that the melted material emerges as liquid droplets several hundred angstroms in diameter, which atomize in less than a nanosecond.
Abstract: We describe a simple imaging technique that can be used to photograph ultrafast processes with time resolution determined by the duration of pump and probe laser pulses. We demonstrate this technique by photographs having 100-fsec time resolution of a silicon surface undergoing melting and evaporation following intense excitation by an ultrashort laser pulse. These photographs resolve the increase in surface reflectivity caused by surface melting both temporally and spatially. Material evaporation from the melted surface further alters the image of the surface by absorbing and scattering the illuminating laser light. Our analysis of this selectively imaged light suggests that the evaporated material emerges as liquid droplets several hundred angstroms in diameter, which atomize in less than a nanosecond.
181 citations
TL;DR: In this article, the authors used impulsive stimulated Raman scattering (ISRS) to detect coherent optic phonons by femtosecond time-resolved observations of optic phonon oscillations and dephasing.
170 citations
AT&T1
TL;DR: In this paper, a new approach to far-infrared spectroscopy is described that uses extremely short farinfrared pulses to measure the dielectric properties of materials, which is equivalent to having a tunable laser in the spectral range from 0.1 to 2 THz.
Abstract: A new approach to far-infrared spectroscopy is described that uses extremely short far-infrared pulses to measure the dielectric properties of materials. Optical rectification of femtosecond optical pulses is used to produce a Cerenkov cone of pulsed far-infrared radiation of approximately one cycle in duration in the terahertz spectral range. The coherent detection of the electric field of these far-infrared pulses by electro-optic sampling provides a capability for measuring precise changes in the shape of the waveform following reflection or transmission from materials. This method, which is equivalent to having a tunable laser in the spectral range from 0.1 to 2 THz, is illustrated by the measurement of the dielectric response of a solid-state plasma in n-type germanium and a GaAs/GaAlAs multi-quantum-well superlattice.
133 citations
TL;DR: Femtosecond techniques permitting the generation of intense optical pulses tunable from the near UV to the near IR are presented in this paper, and their implications for chemistry, biology, and solid-state physics are discussed.
Abstract: Femtosecond techniques permitting the generation of intense optical pulses tunable from the near UV to the near IR are presented. Implications for chemistry, biology, and solid-state physics are discussed. Specific cases are developed for applications such as the comparison of time-resolved polarization and absorption studies in photoexcited GaAs or malachite green in water.
106 citations
TL;DR: In this paper, the bleaching dynamics of organic dye molecules in solution have been investigated using 70 fs pulses from a colliding pulse mode-locked ring dye laser, and a fast partial recovery was observed.
87 citations
TL;DR: Femtosecond transform limited light pulse propagation in vacuum is described in scalar approximation of diffraction theory in this article, where evolution of the spatial and temporal characteristics of the pulse are presented.
84 citations
TL;DR: In this paper, a method for the generation of tunable femtosecond dye-laser pulses that should be applicable to the large class of visible and near-infrared dyes that can be pumped by a frequency-doubled Nd:YAG laser was described.
Abstract: Dye-laser pulses of duration less than 300 fsec and tunable over a range of 400 A have been generated by synchronous pumping with the ultrashort pulses from the fiber-optically compressed second harmonic of a Nd:YAG laser. Optical pulses as short as 210 fsec are reported in this ultrashort-pulse-pumping arrangement that does not require the use of saturable absorbers. With continuous temporal tuning of the duration of the compressed pump pulses, we have made the first reported investigation of the dynamics of synchronous mode locking as a function of pump-pulse width. We describe a method for the generation of tunable femtosecond dye-laser pulses that should be applicable to the large class of visible and near-infrared dyes that can be pumped by a frequency-doubled Nd:YAG laser.
72 citations
TL;DR: In this paper, a new oscillator and amplifier capable of providing 10 MW of power at repetition rates in excess of 1 kHz was proposed. But the power consumption of the amplifier was only 250 nJ of energy.
Abstract: High-repetition-rate laser pulse amplifiers are desirable for investigations of weak signals because of the ability to use ultrasensitive lock-in detection. We have developed a new oscillator and amplifier capable of providing 10 MW of power at repetition rates in excess of 1 kHz. By focusing this pulse we have obtained the white-light continuum with as little as 250 nJ of energy.
71 citations
TL;DR: In this paper, the damping time of the lowest transverse optic phonon has been determined directly from the decay rate of these oscillations, which establishes an intrinsic speed limit for the electro-optic response of this material.
Abstract: Coherent lattice vibrations in lithium tantalate have been observed directly in the time domain by use of femtosecond optical pulses and the electro-optic effect to coherently excite and detect phonon polaritons. The damping time of the lowest transverse optic phonon has been determined directly from the decay rate of these oscillations. This measurement establishes an intrinsic speed limit for the electro-optic response of this material.
TL;DR: In this article, the femtosecond pulse excitation of cis-stilbene at 312.5 nm yields a transient absorption in the visible with a 1.35 ps lifetime.
TL;DR: The dispersive effects of high-reflectivity broadband mirrors on femtosecond optical pulses have been analyzed for three different multilayer structures and shows high distortion of the pulse profile, a frequency chirp, and a broadening as high as a factor of 5.6 within the high-dispersion region.
Abstract: The dispersive effects of high-reflectivity broadband mirrors on femtosecond optical pulses have been analyzed for three different multilayer structures. In each case the high-reflectivity zone can be divided into two different regions symmetrically located around the mirror central frequency: high-dispersion and low-dispersion regions. The calculated temporal behavior of the reflected pulse shows high distortion of the pulse profile, a frequency chirp, and a broadening as high as a factor of 5.6, due to a single reflection, within the high-dispersion region. The use of these types of mirror should therefore be strictly limited to their low-dispersion side.
TL;DR: In this paper, the authors considered the initial phases in the creation of laser-produced plasmas and studied the dynamic behavior of atoms and phase transitions in the picosecond and femtosecond regime.
Abstract: The primary interaction is the absorption of photons by electrons. In metals free-free transitions increase the energy of the electron gas. In semiconductors and insulators electron-hole pairs are created, if the photon energy exceeds the band gap. If it is less, only multiphoton processes can initiate energy transfer from the light beam. In nearly all solid materials Auger processes and electron-phonon interactions occur on a picosecond time scale for the high density and energy of the carrier gas created by intense short laser pulses. Thus melting and evaporation of the material can occur on this time scale. These processes may be considered as the initial phases in the creation of laser produced plasmas. They have been studied by time-resolved measurements of the complex index of refraction, by electron and ion emission, by second harmonic generation, by electrical conductivity and other techniques. Fast time resolution is essential. The dynamic behavior of atoms and phase transitions in the picosecond and femtosecond regime has been opened up for experimental investigation.
TL;DR: In this article, the authors present a theoretical calculation which demonstrates that optical solitary waves can propagate in an optical fiber well into the femtosecond regime and show that the optical fiber which can support such a wave must exhibit negative fourth-order dispersion (βIV0e < 0) and must be used close to appropriate operating points.
Abstract: We present a theoretical calculation which demonstrates that optical solitary waves can propagate in an optical fiber well into the femtosecond regime. Dispersive effects up to fourth order have been considered and more importantly, the ‘‘slowly varying envelope’’ approximation is not invoked. The optical fiber which can support such a wave must exhibit negative fourth‐order dispersion ( βIV0e <0) and must be used close to appropriate ‘‘operating’’ points. Use of such waves in optical fiber communication systems may finally result in the full exploitation of the bandwidth of light.
TL;DR: The use of optical pulses as short as 16 fsec for time-resolved reflectometry studies of multiple-layer dielectric mirror coatings andounced pulse-distortion effects have been observed following reflection from broadband dielectrics.
Abstract: We describe the use of optical pulses as short as 16 fsec for time-resolved reflectometry studies of multiple-layer dielectric mirror coatings. Pronounced pulse-distortion effects have been observed following reflection from broadband dielectric mirrors.
TL;DR: Combining holographic and femtosecond laser pulse compression technology, gigawatt peak power and 85-fsec bandwidth-limited laser pulses were obtained.
Abstract: Combining holographic and femtosecond laser pulse compression technology, gigawatt peak power and 85-fsec bandwidth-limited laser pulses were obtained. Pulse compression was achieved using a pair of high diffraction efficiency volume phase transmission holographic gratings.
TL;DR: In this article, femtosecond optical pulses are used to discriminate temporally among the different processes involved in the third-order-induced polarization, and tensor elements deduced from the instantaneous measured components are compared with previous frequency-domain experimental results.
Abstract: Intense femtosecond optical pulses are used to discriminate temporally among the different processes involved in the third-order-induced polarization. The tensor elements deduced from the instantaneous measured components are compared with previous frequency-domain experimental results.
01 Mar 1985
TL;DR: In this paper, femtosecond techniques allowing to generate intense optical pulses from the near UV to the near infrared and their use in the monitoring of ultrafast photochemical reactions at this same time scale.
Abstract: We present femtosecond techniques allowing to generate intense optical pulses from the near UV to the near infrared and their use in the monitoring of ultrafast photochemical reactions at this same time scale. Chromophores embedded in micellar solution are photoionized by femtosecond UV pulses. After the charge separation (electron), photoelectrons are shown to react with water molecules in aqueous phase of micelles and are then used to trigger and monitor the first steps of electron transfer in semi-organized micellar solutions.
TL;DR: Theoretical and experimental investigations were made of chirping (linear frequency modulation of the carrier frequency in a pulse) of radiation from an optical parametric oscillator pumped by linearly chirped pulses as mentioned in this paper.
Abstract: Theoretical and experimental investigations were made of chirping (linear frequency modulation of the carrier frequency in a pulse) of radiation from an optical parametric oscillator pumped by linearly chirped pulses. It is shown that such an oscillator is an efficient converter of a pump chirp into a linear chirp of the output pulses. The latter may be stronger than the pump chirp, which provides new opportunities for mastering the femtosecond range.
TL;DR: Femtosecond laser pulses and dye fluorescence kinetics were used to characterize the time response of an ultrafast streak camera system as a function of an entrance slit in this article.
Patent•
28 Feb 1985
TL;DR: In this article, the authors present a system for measuring laser pulse durations in the range of ten nanoseconds to one femtosecond to an accuracy of one femtocond.
Abstract: A system for measuring laser pulse durations in the range of ten nanoseconds to one femtosecond to an accuracy of one femtosecond, includes a primary pulse sampler, a ten component beam splitter array, optical delay lines whose settings are microprocessor controlled, a ten section interaction chamber with ten sets of ion detectors and a pulse envelope and pulse energy display monitors. The system has applications in chemistry, calibration of fast timing circuits and in the development of short pulse lasers.
TL;DR: In this paper, a mathematically more rigorous treatment of this problem is presented where a nonlinear differential equation is derived for the general solution in the approximation of Klima and Petrzilka.
Abstract: A mechanism has been discussed before by Dragila and Hora where very short laser pulses in a homogeneous plasma can be absorbed without collisions by the action of time dependent nonlinear forces. The resulting absorption lengths are of interest for the study of femtosecond neodymium glass laser pulses or the sub-picosecond carbon dioxide laser pulses which are now available. A mathematically more rigorous treatment of this problem is presented where a nonlinear differential equation is derived for the general solution in the approximation of Klima and Petrzilka. The ordinary differential equation can be solved exactly. With reasonable initial conditions, the solutions are similar to those of Dragila and Hora and are evaluated numerically for cases of experimental interest.
01 Feb 1985
TL;DR: In this paper, a magnetic focusing streak tube has been developed aiming at femtosecond time resolution, and an unique focusing method was used in order to improve the defocusing of the beam induced under such sweeping conditions.
Abstract: A magnetic focusing streak tube has been developed aiming at femtosecond time resolution. In focusing of photoelectron beam swept very fast, an unique focusing method has been used in order to improve the defocusing of the beam induced under such sweeping conditions. The limiting time resolution better than 500fs has been experimentally obtained.
TL;DR: In this paper, a numerical investigation is made of the spreading of femtosecond light pulses in some nonlinear optical crystals, and also in air and water, and the published experimental values of the refractive index are used in these calculations.
Abstract: A numerical investigation is made of the spreading of femtosecond light pulses in some nonlinear optical crystals, and also in air and water The published experimental values of the refractive index are used in these calculations The dispersion spreading lengths are determined The characteristics of spreading of frequency-modulated femtosecond pulses are established
Journal Article•
01 Jan 1985
TL;DR: In this paper, the application of femtosecond optics to the measurement and characterization of the electronic properties of materials and devices is reviewed with emphasis on new approaches to the generation and detection of extremely fast electromagnetic transients.
Abstract: The application of femtosecond optics to the measurement and characterization of the electronic properties of materials and devices is reviewed with emphasis on new approaches to the generation and detection of extremely fast electromagnetic transients. Specific topics discussed are: (i) the use of the inverse electro-optic effect for electrical pulse generation, (ii) the intrinsic speed of response of electro-optic materials, and (iii) a new approach to far-infrared spectroscopy which uses time-domain measurements of single-cycle pulses.
TL;DR: In this paper, the femtosecond measurement techniques and the application of these methods to the study of highly excited semiconductors are described, and the authors describe the recent advances in femto-conditional measurement techniques.