Tunable Ultrashort Pulses Research Articles

Intense subpicosecond pulses tunable between 4 μm and 20 μm generated by an all-solid-state laser system

The generation of widely tunable ultrashort mid-infrared pulses with intensities sufficient for a substantial excitation of infrared states is discussed. Single pulses of 1 ps duration and an energy of 7 mJ from an APM mode-locked Nd:glass laser with regenerative amplifier (repetition rate 4 Hz) serve as pump pulses. A three-path optical parametric generator pumped by the second harmonic of the Nd-laser produces tunable near infrared pulses. Subsequent down conversion in GaSe provides pulses of 0.7 ps duration tunable between 4 μm and 20 μm. Energies up to 25 μJ are measured.

Parametric generation of femtosecond and picosecond pulses for spectroscopic applications

Parametric three-photon interaction provides continuously tunable ultrashort pulses in extended spectral regions from the UV to the mid-IR. We focus on parametric systems operating in the pulsed mode. Optical parametric oscillators pumped by intense microsecond trains of subpicosecond pulses exhibit favorable properties. We present data on a pulsed optical parametric oscillator that has a wide tuning range from 0.7 to 1.8 μm, a conversion efficiency of a few percent, and a minimum pulse duration of as low as 65 fs. Larger tuning ranges are covered by subsequent downconversion or parametric amplification. We discuss the generation of ≲1-ps pulses at wavelengths between 2 and 18 μm. Finally, the potential of parametrically generated IR pulses is demonstrated by several applications.

Generation of tunable ultrashort light pulses by a laser with dynamic distributed feedback in an external ring resonator

Experimental and theoretical studies were made of the time and energy characteristics of a rhodamine 6G dye ring laser with optically induced distributed feedback, pumped synchronously by a train of ultrashort pulses from an actively mode-locked YAG:Nd laser with intracavity second harmonic generation. Narrow-band (~ 0.08 nm) generation of ~ 10 ps ultrashort pulses, tunable in the 568–602 nm range, and with a divergence of ~ 0.4 mrad was achieved. The energy efficiency was ~ 4% for each of the two output beams at a pump energy of 25 μJ. Under optimal conditions the duration of the output pulse was approximately twenty times shorter than that of the pump pulse. The results of the calculations using the proposed model show a good agreement with the experiments.

Picosecond phosphate glass laser with controlled parameters

Tunable ultrashort laser pulses were generated in GLS22P phosphate neodymium glass with a total pumped length of 160 mm emitting at wavelengths 1.046?1.09 ? and KNFS glass of length 40 mm emitting at wavelengths 1.05?1.07 ?. The ultrashort pulses were almost bandwidth-limited, had durations in the range 6?250 psec, and were characterized by a spectral width 0.15?6 cm?1. Moreover, tunable ultrashort pulses with a spectral width 30?40 cm?1 were also generated.

Efficient generation of tunable infrared ultrashort light pulses by nonlinear frequency conversion in atomic cesium vapor

Electron stimulated Raman scattering in atomic cesium vapor was used in efficient conversion of the freqeuncy of the second harmonic to the infrared range in the case of picosecond YAG and neodymium phosphate glass lasers. The tuning range of ultrashort pulses was 2.21-2.55μ, the spectral width of the output pulses did not exceed 2 cm−1, and the quantum efficiency of the conversion process was 10%. In addition to tunable ultrashort pulses, picosecond pulses at fixed wavelengths of 3.1 and 0.88μ were generated.

Generation of synchronized independently tunable ultrashort light pulses using an antiresonant ring cavity

Various solutions have been proposed in recent years to the problem of producing two synchronous but independently tunable trains of ultrashort light pulses. We suggest that the use of a single saturable absorber situated at the midpoint of an antiresonant ring shared by the different cavities of two mode-locked lasers may offer another approach to the problem.

Optically biased tunable femtosecond dye laser and spectral windowing of the compressed second harmonic of Nd:YAG

We describe a technique for enhancing tunable ultrashort pulse pumped dye laser performance based on the use of "long" pump pulses to optically bias the cavity toward minimal losses. Increases in dye laser output power of 155 percent and powers as high as 125 mW have been measured with pulse durations under 300 fs. Optical pulses as short as 180 fs are reported for this ultrashort pulse pumped dye laser oscillator. We also report the first measurements of the spectral windowing of compressed 532 nm pulses for temporal pulse shaping, in the optimal group velocity dispersion limit. Temporal pulse shaping is demonstrated with small losses in power and minimal pulse broadening.

Generation of tunable ultrashort pulses in the ultraviolet with the aid of distributed feedback dye laser excited by an N2 laser

The aim of the study is to analyze spectral concentration of radiation (SCR) on the basis of the assumption that it arises on account of nonlinear resonant self-action of the radiation generated in the in-resonator cuvette with absorbing gas. SCR in a dye laser with an in-resonator cuvette close to the absorption line of the material filling this cuvette is of considerable interest both for quantum electronics and for in-resonator spectroscopy. The authors show that if the basic mechanism responsible for SCR is assumed to be resonant self-action of the laser radiation in the cuvette with absorbing gas, the spectral picture depends significantly on the magnitude and sign of the repolarization coefficient of the transition close to which SCR is formed.

Electron stimulated Raman scattering and four-wave interaction in barium atomic vapor pumped by tunable ultrashort light pulses

A phosphate neodymium glass laser emitting picosecond pulses tunable in the 1.05–1.07 μ range was developed to study nonlinear optical processes in atomic barium vapor. Its temporal characteristics were investigated using a modified second harmonic beam method. Electron stimulated Raman scattering and four-photon parametric conversion in atomic barium vapor were used to obtain efficient conversion of the third harmonic of the picosecond phosphate laser (350–356 nm) to the Stokes (580–600 nm) and anti-Stokes (250–253 nm) waves. The highest conversion quantum efficiency for the Stokes wave was 15%. Electron stimulated Raman scattering in an (6s2)1S–(6s7s)1S–(6s6p)1P0 system, having a strongly forbidden first transition, was recorded for the first time. In the same system, two-photon pumping generated four-photon parametric superradiance and it was found that the signal and idler waves had anomalously broad spectra (wider than 100 cm−1).

Generation of tunable ultrashort pulses in a dynamic distributed feedback laser

A study was made of the operation of a dynamic distributed feedback (DFB) laser utilizing dye-activated polyurethane and pumped by a train of ultrashort pulses from a YAG:Nd3+ laser. An interference system with division of the pump pulse duration was used to produce the dynamic DFB. Direct measurements were made of the duration of the generated pulses using an Agat-SF streak camera and it was found that the duration of the output pulses was considerably shorter (up to four times) than that of the pump pulses. Tuning in the 560-600 nm range with an ultrashort pulse duration of ~8 psec, a divergence of ~1 mrad, and a lasing efficiency of ~ 3 % were achieved. The evolution of the ultrashort pump and lasing pulse trains indicated that a thermal phase grating had no influence on the operation of this laser.

Applications of synchronously pumped dye-lasers to time-resolved emission and absorption spectroscopy

Methods of generation and measurement of tunable ultrashort light pulses from c.w. synchronously pumped dye-lasers are described. Conditions for optimal pulse shape are discussed and experiments to determine absolute dye-laser cavity length, pulse-to-pulse reproducibility and pulse substructure are described. Methods of applying synchronously pumped dye-lasers to time-resolved emission and absorption spectroscopy are described. Results on the orientational motion of oxazine in a variety of solvents are described and discussed, in terms of the hydrodynamic boundary condition. Fluorescence data on the solvent-dependent excited-state dynamics of anilinonaphthalene sulphonate are presented and discussed. It is suggested that the very rapid radiationless transition observed in aqueous solution corresponds to electron transfer from the excited molecule to a nearby solvent trap.

Generation of tunable ultrashort pulses by synchronous pumping of dye lasers

An experimental investigation was made of some relationships governing the generation of tunable ultrashort pulses by synchronous pumping of dye lasers. The synchronous pumping was provided by trains of ultrashort pulses of 20–25 psec duration at the second harmonic of a YAG:Nd3+ laser with a repetition frequency of up to 100 Hz. Measurements were made of the power resonances found in the vicinity of equal and multiple resonator lengths, and of the durations, spectral widths, and tuning ranges of the generated pulses.

Generation of a single tunable ultrashort light pulse

A novel system for generating single tunable ultrashort light pulses of high power is described. The pulse train from a mode-locked flashlamp pumped dye laser passes through an amplifier, which is pumped by an N 2 laser. As gain is only available for a few nsec, only one pulse in the train gets amplified. The energy of the resulting single pulse is about 100 μJ.

Temporally coincident ultrashort pulses from synchronously pumped tunable dye lasers

The temporal and spectral character of the picosecond pulses from a dye laser which was synchronously pumped by a frequency-doubled mode-locked Nd:glass laser was studied with an ultrafast streak camera. For matched pump and dye laser cavity lengths, the observed dye pulses were of 15-psec duration and were in very close temporal synchronism with the pump pulses. For deviations from match >0.1 mm, severe aberrations in pulse character began to occur. Spectral tuning of the dye laser was achieved with a narrow-gap etalon. The utility of such lasers in producing two independently tunable time-synchronized ultrashort pulses for parametric frequency generation and spectroscopic studies is discussed.