1,720,995 research outputs found
Generation of a broad amplified spectrum in a femtosecond terawatt Ti : sapphire laser by a long-wavelength injection method
No full textA long-wavelength injection method is proposed that will yield a broad amplified spectrum in a femtosecond terawatt Ti:sapphire laser. By injecting a seed pulse on the red side of the gain peak and amplifying it to a saturated fluence level, we could significantly compensate for the spectral narrowing that is due to the gain-narrowing effect by use of the amplifying characteristics of a positively chirped pulse in a gain-saturated regime, and 20-fs, 3-TW pulses could be demonstrated from a Ti:sapphire laser with two multipass amplifiers. (C) 1999 Optical Society of America [S0740-3224(99)01407-1].This study was supported by the Agency for Defense Development through the Center for Electro-Optics of the Korea Advenced Institute of Sciene and Technology and the ministry of Science and Technology, Kore
Incorporation of a cavity-dumped oscillator in a long-wavelength injected femtosecond terawatt Ti : sapphire laser
No full textA cavity-dumped Ti:sapphire laser was utilized as a front-end oscillator in a femtosecond terawatt Ti:sapphire laser. The increase of the oscillator energy by 30 times helped to reduce the gain narrowing and to suppress the amplified spontaneous emission in a preamplifier. In combination with the long-wavelength injection method (J. Opt. Sec. Am. B 16 (1999) 1220), an amplified spectrum broad enough to support sub-20 fs could be generated at a multiterawatt level, and 20-fs, 3-TW pulses were demonstrated. (C) 2000 Published by Elsevier Science B.V.This work is supported by the Minstry of Science and Technology of Korea Through the Creative Research Initiative Program
Regenerative third-harmonic frequency modulated(FM) mode-locking in a bulk Nd : YLF laser
No full textWe have demonstrated a regenerative harmonic frequency modulated(FM) mode-locking in a bulk Nd:LiYF4 (YLF) laser for the first time. After suppressing the mode competition between positive (up-chirped) and negative (down-chirped) modes using an etalon, a third-harmonic FM mode-locking based on a regenerative feedback loop was realized in a Nd:YLF laser. Stable, self-starting pulses were generated with a duration of 6.5 ps at 1-GHz repetition rate and an average output power of 240 mW at a 1-W laser diode pumping power.This work is supported by the Minstry of Science and Technology of Korea Through the Creative Research Initiative Program
13-fs, 1-MW Ti : Sapphire laser oscillator in a long-cavity configuration
No full textWe generated 13-fs pulses with a peak power of I MW from a long-cavity femtosecond Ti:sapphire laser with 3.7-W pumping. To boost laser energy without degrading the pulse quality from that of a standard laser cavity of 100 MHz, the cavity length was extended by adding four concave mirrors using an image relay scheme, lowering the repetition rate of the oscillator to 27 MHz. The long-cavity laser operating stably with 120-nm spectral width was suitable for the front-end oscillator of a femtosecond chirped-pulse amplification laser.This work is supported by the Minstry of Science and Technology of Korea Through the Creative Research Initiative Program
Generation of nonadiabatic blueshift of high harmonics in an intense femtosecond laser field
No full textBy applying intense 30-fs Ti:sapphire laser pulses to Ar gas well above the saturation intensity for optical-field ionization, a strong blueshift of high harmonics 2 times as large as the laser frequency was generated. A semiclassical calculation showed that the observed large blueshift resulted from a rapidly increasing electric field, existing much earlier in time than the peak of the laser pulse, i.e., a nonadiabatic effect.This research was supported by the Ministry of science and Technology, Korea and by the Agency for Defense Development through the Center for Electro-Optics at KAIS
Time-Frequency Analysis of Chirped Femtosecond Pulses Using the Wigner Distribution Function
No full textInvestigation of soft X-ray emission from Ar clusters heated by ultrashort laser pulses
No full textWe report soft X-ray spectra (4-18 nm) produced by the interaction of 25-100-fs laser pulses at an intensity of up to 7 X 10(16) W/cm(2) with a cryogenically cooled Ar gas jet. New spectral lines from Ar8+, Ar9+, and Ar10+ charge states appeared with decreasing preexpansion gas temperature. A nonlinear increase of X-ray line emission from Ar7+, Ar8+, and Ar9+ was observed with cooling, which saturated below a certain temperature. The drastic change in the spectrum is attributed to efficient collisional heating and collisional ionization of growing, small- to medium-sized (10(2)-10(3) atoms) Ar clusters from the cooled jet. When the laser pulse was extended from 25 to 100 fs we observed considerably stronger emission on lines from high charge states, such as Ar8+, Ar9+, and Ar10+, which suggests that the resonance absorption condition could be reached for the 100-fs pulse
Nonadiabatic blueshift of high-order harmonics from Ar and Ne atoms in an intense femtosecond laser field
No full textA strong blueshift of high-order harmonics was observed when intense femtosecond Ti:sapphire laser pulses were applied to Ar and Ne. The blueshift was systematically investigated for various experimental parameters, such as laser intensity, laser-pulse duration, and gas density. We observed the harmonic blueshifts of two times the laser frequency in the 39th harmonic from Ar and four times the laser frequency in the 85th harmonic from Ne. A semiclassical calculation predicted the inverse proportionality of the blueshift to the laser-pulse duration, which was confirmed in the experiment done with 30 fs and YB fs pulses. The density dependence of blueshift showed that the self-phase modulation in an ionizing medium was not a major factor of the observed blueshift. The experimental results along with theoretical calculations confirmed that the observed blueshift resulted mainly from the nonadiabatic effect due to the rapid increase in the femtosecond laser electric field.This work is supported by the Minstry of Science and Technology of Korea Through the Creative Research Initiative Program
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