Interpulse coherence of picosecond pulses

Interferometric studies of trains of picosecond pulses from dye mode-locked Nd: glass lasers have been made. Both autocorrelation and cross correlation measurements of pulses have been recorded. Even for non-minimum width pulses very high fringe contrast ratios have been obtained for both cases indicating considerable similarity between pulses. It is also concluded that the relative phase shift from pulse to pulse is constant.     

Generator of picosecond laser pulses

The design of the generator of picosecond laser pulses and the results on semiconductor target (ZnSe, CdS, and others) excitation by electric field and electron beam pulses are presented. The maximum power of laser radiation reached 10 kW at pulse durations of 100–200 ps.     

Generation of chirp-free picosecond pulses

The frequency spectrum of moderately chirped laser pulses depends upon the portion of the beam which is accepted by the spectrometer. Observation of the development of the chirp in a mode-locked pulse train allows to determine the small incipient chirp of early pulses. A product, bandwidth times pulse duration, of 0.47 ± 0.03 is consistently observed for single pulses switched from a passively mode-locked Nd-glass system.     

Amplification of picosecond dye laser pulses

Small signal and saturated gains of picosecond pulses in Rhodamine dye amplifiers have been measured. A 17 cm amplifier produces a maximum small signal gain of ≈20, and with three amplifiers in series, peak pulse powers of > 3 GW are obtained. Mode-locking of Rhodamine 6G in the spectral range 575–600 nm is improved by employing DQOCI as saturable absorber.     

Controlling the width of picosecond laser pulses

The relaxation time τ_R of the saturable dye used to mode-lock a Nd: YAG laser has been changed using different dyes or dye solvent mixtures and the laser bandwidth Δω changed by the insertion of an etalon. The pulse duration τ_p was approximately transform-limited for τ_R<2π/Δω but increased to about twice this value when 2π/Δω<τ_p<τ_R. No significant increase in pulse duration was observed for τ_R?2π/Δω but multiple pulses were generated within each round-trip-transit-time.     

Acoustic activity effect for picosecond soliton-like pulses

A theoretical analysis is made of the acoustic activity for interfering picosecond acoustic soliton-like pulses of down to a single oscillation period. An analysis is made of the case where these pulses propagate parallel to an external magnetic field and one of the acoustic axes in a cubic crystal containing paramagnetic impurities having effective spin S = 1. Allowance is made for natural, magnetic (Faraday), and cross acoustic activity. This cross activity is caused by the significant spatial nonlocality of the spin-phonon interaction for such short pulses in crystals having no center of inversion in the presence of paramagnetic impurities. A system of nonlinear equations is obtained for the transverse and longitudinal components of the strain in the form of a coupling between the “differentiated” nonlinear Schrödinger equation (with nonlinearity after the derivative sign) and the Korteweg-de Vries equation which generalizes the known systems of long-short-wavelength resonance to the case where the slowly varying envelope approximation is not valid. An approximate solution of this system is used to study the structure of an elastic soliton-like pulse whose transverse component has a rotating plane of polarization, which propagates under conditions of nonlinear coupling with the longitudinal strain.     

Spatial photorefractive solitons with picosecond laser pulses

We report on the formation of spatial optical solitons in photorefractive media using picosecond laser pulses. Solitons are generated with laser pulses in the visible and infrared wavelength region using photorefractive strontium barium niobate. The dynamics of the soliton formation and the region of existence is studied in detail.     

Direct ninth harmonic conversion of picosecond laser pulses

Direct ninth harmonic conversion of picosecond laser pulses is obtained for the first time. Using sodium vapor, phase- matched ten-photon process by Nd³⁺: glass laser pumping is realized. Effective ninth-order nonlinear susceptibility of the order of x⁽⁹⁾_eff ～ 10^-64 ESU is estimated.     

大芯径石英光纤中皮秒脉冲激光的自聚焦

本文报道了对大芯径石英光纤中皮秒脉冲激光自聚焦现象的实验研究和理论分析.文中测量了自聚焦先场的近场光强轮廓,研究了自聚焦光场的时域和频域性质,并对环形自聚焦光场的成因进行了解释.     

Heating of opaque surfaces by picosecond laser pulses

Received: 5 June 1997/Accepted: 13 June 1997     

ps参量放大效应

本文报道用0.53μm波长超短脉冲序列泵浦角度调谐的LiNbO_3参量晶体,获得1%单程参量放大能量转换效率,并在0.8～1.6μm范围测得参量信号光和空载光波长调谐曲线.     

Dynamics of Na clusters in picosecond laser pulses

We investigate the electronic and ionic dynamics of Na clusters under the influence of a laser pulse in the range 100 femtoseconds to picoseconds. The dynamics is described by means of the time-dependent local-density approximation coupled to ionic molecular dynamics (TDLDA-MD). Variation of pulse length allows us to explore the time scales of ionic motion in a manner similar to pump and probe experiments. Resonant enhancement of electron emission serves as a measure for the time scale of Coulomb explosion. Received: 3 July 2001 / Published online: 10 October 2001     

Generation of rayleigh waves by picosecond laser pulses

In this paper we present the fundamental mechanism which we hold responsible for generation of high frequency Rayleigh waves by picosecond laser pulses on a single crystal surface of Silicon. These Rayleigh waves have been recorded as ripples frozen out on the surface of the crystal upon irradiation with a focused cw mode-locked laser.     

新型金属团簇(Et_4N)_3WOS_3Cu_3I_4的皮秒光限幅特性研究

应用波长为532nm,脉冲宽度为40ps的激光脉冲研究了新型金属团簇(Et4N)3WOS3Cu3I4的光限幅性能。实验结果表明,该金属团簇在皮秒激光脉冲的作用下,具有很强的光限幅特性。利用非线性吸收的唯象理论对实验结果进行了分析。     

Spectral holography of pico- and nanosecond optical pulses

Recording and reconstruction of pico- and nanosecond pulses have been accomplished with spectral holography. The development of spectral holography in the nanosecond time-domain was achieved while using high-spectral-resolution equipment based on a Fabry-Perot etalon with a side entrance/exit. The recognition of the shaped nanosecond light pulses was also realized.     

Efficient generation of narrow-bandwidth picosecond pulses by frequency doubling of femtosecond chirped pulses

We demonstrate efficient generation of picosecond narrow-bandwidth pulses by frequency mixing of broadband opposite chirped pulses in a type I doubling crystal. This procedure allows us to produce picosecond pulses that are perfectly synchronized with femtosecond pulses. The experiment shows a decrease of the initial bandwidth by a factor of more than 30, while a high conversion efficiency is maintained.     

Optical and photocurrent spectroscopy with picosecond strain pulses

This paper gives an overview of optical experiments using picosecond strain pulses. The strain pulses, which propagate with the sound velocity, are incident on a semiconductor nanostructure and induce an ultrafast shift of the exciton resonance energy by an amount, that exceeds the spectral width of the corresponding optical transition. When the duration of the high-amplitude strain pulse is long enough compared with the coherence time of the optical resonance, modulation of the resonance takes place adiabatically and exciton energy can be accurately defined at each momentary position. If the coherence time exceeds the characteristic time of the strain pulse, a non-adiabatic regime is realized and the exciton cannot be related to an optical transition with a specific photon energy. In more detail, we describe the recent experiments on the gating of photocurrent in a tunneling p-i-n device and the generation of THz polariton sidebands in an optical microcavity strongly coupled to the excitons in an embedded quantum well. These two experiments represent, respectively, examples of adiabatic and non-adiabatic behaivior of excitons in the presence of the high-amplitude picosecond strain pulse.