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Filament-induced periodic surface structures are generated on a wide variety of materials with near-IR and UV lasers. The surface structure features demonstrate the relation to laser wavelength and polarization and energy distribution in a filament.
Multi-Joule level SBS sub-phonon lifetime pulse compression is demonstrated with a energy-scalable generator-amplifier setup to obtain 1.3J, 170ps (close to half of the phonon lifetime) laser pulses at 532nm.
Ultrashort pulse diagnostic require a nonlinear crystal satisfying the conflicting requirements of fidelity in reconstruction and efficiency. It is shown that correct autocorrelations can be obtained with longer crystals than generally assumed.
Intracavity phase interferometry measures a beat frequency between two counter circulating pulses within a mode-locked cavity. A modification of sensitivity through insertion of resonant linear dispersion is experimentally demonstrated, while the pulse velocity remains unchanged.
The shock wave created by a high energy UV filament is sufficient create a low pressure absorber enabling higher resolution laser induced breakdown spectroscopy, through reduction or pressure broadening. Isotopic selectivity is demonstrated.
A new type of interferometric spectrograph is realized by placing a transmission grating into a Sagnac interferometer. Two diffracted orders propagate in opposite directions; the Fizeau interferogram at the output yields a heterodyned spectrum.
When a transmission grating is placed in a Sagnac interferometer, two diffracted wavefronts propagate in opposite directions and interfere at the output, forming a Fizeau fringe pattern. This interferogram contains spectral information heterodyned around a center wavelength. By changing the design, high resolving power or broad spectral range can be accomplished.
We discuss implementations of mode-locked ring lasers, their stabilization via passive optical cavities, and their applications to the development of ultrasensitive sensors.
Measuring the continuum polarization against pulse ellipticity of a laser filament is introduced as a new paradigm for quantifying nonlinearities in filamentation such as ionization paths, molecular alignment, nonlinear index and field intensity.
An uncoated glass etalon inserted in a mode-locked laser results generating two nested frequency combs. The ratio of their frequencies, insensitive to external parameters, is an accurate measure of the optical path in the etalon.
Pulse-front-tilt and negligible pulse-width spread across the laser beam are reported, both experimentally and numerically, for pulses from a Q-switched unstable resonator with a variable-reflectivity-mirror under different operation conditions.
Supercontinuum generation by filamentation in molecular gases is optimized by studying the ellipticity of the pulse polarization during the interaction with the species of the gas medium via strong field ionization and molecular alignment effects.
Impulsive rotational/vibrational Raman scattering of molecules excited by IR filaments and thereafter probed by a narrow line-width UV beam is proposed. We show results of rotational Raman scattering of air molecules for preliminary demonstration.
A modified Spatial Heterodyne Spectrometer (SHS) is used for measuring atomic emission spectra for instance in LIBS experiments. This device is basically a Fourier Transform Spectrometer, but the Fourier transform is taken in the directions perpendicular to the optical propagation and heterodyned around one specific wavelength. Therefore, this device uses no movable parts. The resolution of the device...
Nonlinear interaction resulting in unusual propagation properties of high power pulsed lasers beams can be exploited for remote and high resolution spectroscopy. Long range interrogation of solids and vapors, for instance by stimulated backward Raman scattering, requires a thorough understanding of the propagation of intense pulses in the atmosphere. Self trapping of femtosecond (in the near IR) and...
It is shown that auto-stabilization of an intracavity pumped Optical Parametric Oscillator can be achieved by exploiting the cascaded nonlinearities that are at the root of phase instabilities of this system.
We experimentally demonstrate SBS pulse compression in water from 10 ns, 2.3 J to 300 ps, 1.2 J. To our best knowledge, this is the highest compressible energy that has been achieved at 532 nm.
We study the dynamics of the plasma generated with 800nm filaments of 60fs in a pump-probe system in nitrogen cell. We see the effect of molecular revival and plasma dynamics on beam profile and spectrum.
Using a streak camera, and combining over 1,000 synchronized frames, 4D (2 D space, time in ps and wavelength) movies of the light and plasma emission in the wake of filaments are produced.
A simple real-time resonance tracking method is described and experimentally demonstrated for stable single axial mode operation of an injection-seeded Q-switched Nd:YAG laser. We have achieved stable single axial mode operation with mW of seeding power in noisy environment over hours. The mode selectivity dependence on finite Q-switch opening time is demonstrated and quantitatively modeled for Q-switch...
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