ABSTRACT
A simple and compact spectral-broadening system is presented that is based on a single-stage statically pressurized Ar filled hollow core fiber. By optimizing the inner diameter of the hollow core fiber, a bandwidth of 300 nm is obtained. This is the broadest bandwidth known to date with millijoule level energy near the 1-µm wavelength by a single stage gas filled hollow core fiber.
ABSTRACT
Stimulated Raman scattering driven by differential coupling of two phonon modes has been demonstrated. These phonon modes are coherently and strongly coupled by external fields via two-phonon excitation at the first Brillouin zone boundary. Up to 11th order of sidebands and a supercontinuum covering entire visible region have been observed. The original Stokes and anti-Stokes lines by the single-phonon stimulated Raman scattering were significantly suppressed.
ABSTRACT
A two-dimensional spectral-shearing interferogram has been acquired instantaneously by frequency- and time-resolved sum-frequency conversion where the phase-matching angle and transverse-delay of crossed-pump beams in a nonlinear crystal serve as frequency-time decomposed imaging. The two spectrally sheared components travel the same path after upconversion. A picoseconds delay-scanned interferogram is accumulated on a 2D image sensor.
ABSTRACT
A long-time-range spectral-shearing interferometry has been demonstrated by frequency mixing with two-color monochromatic fields. Strongly chirped pulses with quadratic and cubic phase distortion have been characterized. A linearly chirped pulse having 2.2 ps (full duration of 6 ps) has been measured with a coaxial two-color field generated by a narrow-gap passive etalon. Substantial extensions in the time range can be expected with a highly coherent two-color source, i.e., frequency stabilized lasers, or two longitudinal modes in the frequency comb.
Subject(s)
Interferometry/instrumentation , Lasers , Optical Devices , Signal Processing, Computer-Assisted/instrumentation , Computer Simulation , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Light , Models, Theoretical , Scattering, RadiationABSTRACT
Oxidative mutation is mainly induced by reactive oxygen species (ROS), such as the superoxide anion radical (O(2)(-)) and hydrogen peroxide (H(2)O(2)). However, in Escherichia coli (E. coli), ROS are eliminated by enzymes such as superoxide dismutase and catalase, which are coded by sodAB and katEG genes. In this study, to detect mutagens that induce oxidative mutation, a mutant (WP2katEGsodAB) with katEG and sodAB deleted was constructed by gene manipulation of E. coli WP2. H(2)O(2) and menadione sodium bisulfite generated mutation in WP2katEGsodAB but not in WP2. o-Phenylphenol (OPP) and its metabolites (phenylhydroquinone (PHQ) and phenyl-1,4-benzoquinone (PBQ)), which had been shown to be negative in the Ames test but reported to be carcinogenic, induced mutation in WP2katEGsodAB but not in WP2. These results suggest that the new assay may be useful for the detection of oxidative mutagens.
Subject(s)
Biphenyl Compounds/toxicity , Escherichia coli/genetics , Fungicides, Industrial/toxicity , Mutation , Oxidative Stress , Bacterial Proteins/genetics , Benzoquinones/toxicity , Biphenyl Compounds/metabolism , Catalase/genetics , DNA Damage , Drug Resistance, Bacterial/drug effects , Drug Resistance, Bacterial/genetics , Escherichia coli/drug effects , Escherichia coli Proteins/genetics , Fungicides, Industrial/metabolism , Hydrogen Peroxide/toxicity , Hydroquinones/toxicity , Methylnitronitrosoguanidine/toxicity , Microbial Viability/drug effects , Organisms, Genetically Modified , Superoxide Dismutase/genetics , Vitamin K 3/toxicityABSTRACT
Femtosecond pulse amplification by a two-photon arranged photorefractive amplifier (TAPA) has been demonstrated. A gain bandwidth of 32 THz has been achieved with an extraction efficiency of 27 %.
ABSTRACT
All-optical phase correction scheme for few-cycle optical pulses has been proposed. The temporal phase structure of a phase-modulated pulse is recorded as spatial index modulation in a two-photon recording medium. This scheme drastically relaxes complicacy in stretcher design for few-cycle chirped pulse amplification (CPA) systems.
Subject(s)
Amplifiers, Electronic , Fiber Optic Technology/instrumentation , Models, Theoretical , Signal Processing, Computer-Assisted/instrumentation , Computer Simulation , Equipment Design , LasersABSTRACT
A diode-pumped chirped-pulse regenerative amplifier with a cooled Yb:YLF crystal has been developed. The output pulse energy is 30 mJ at 20-Hz repetition rate. A high effective extraction efficiency of 68% is obtained, which is attributed to reduced saturation fluence at low temperature and to a high effective pulse energy fluence during regenerative amplification. After pulse compression by use of a parallel grating pair, 18-mJ pulse energy and 795-fs pulse duration are obtained.
ABSTRACT
We have demonstrated a diode-pumped Yb:LiYF4 laser oscillator at liquid nitrogen temperature in free-running mode. The obtained laser gain was 21 cm-1, which was 15 times as high as that at room temperature. The effective tuning range was broadened to 35 nm due to absorption spectral narrowing.
ABSTRACT
Schemes to generate a frequency-domain phase-conjugate pulse by frequency mixing prechirped pulses are proposed. A femtosecond timereversed replica is generated by the temporal-frequency-converted optical parametric processes.
