Vladimir Kartazaev

Ultrashort Laguerre-Gaussian pulses with angular and group velocity dispersion compensation

Coherent optical vortices are generated from ultrashort 6.4 fs pulses. Our results demonstrate angular dispersion compensation of ultrashort 6.4 fs Laguerre-Gaussian (LG) pulses as well as what is believed to be the first direct autocorrelation measurement of 80 fs LG amplified pulses. A reflective-mirror-based 4f-compressor is proposed to compensate the angular and group velocity dispersion of the ultrashort LG pulses.

Spectral, temporal, and coherence properties of supercontinuum generation in microstructure fiber

Spectral, temporal, and coherence properties of supercontinuum (SC) generation in a microstructure fiber were experimentally studied with low-peak-power femtosecond pump pulses. By a spectral interferometry approach, the degree of mutual (axial) spectral coherence was observed to be low for solitons with a pump wavelength region close to the zero-dispersion wavelength (ZDW) and was observed to be high for the solitons with a pump wavelength region far from the ZDW. The generation of multiple frequency channels was experimentally demonstrated by dual time-delayed low-peak-power pump pulses near and far from the ZDW for possible application in a wavelength-division-multiplexing network.

Supercontinuum generated in calcite with chirped femtosecond pulses

Effects of pulse chirping on the dynamic of supercontinuum (SC) spectra generated by femtosecond laser pulses at 800 nm in calcite are studied. When an 80 fs laser pulse is stretched to more then 130 fs by introducing positive or negative chirp, a strong and sharp spectral peak in the blue wing of the SC spectra is generated. The wavelength of this spectral peak is tuned by introducing chirp and pulse energy.

Changes of collagen, elastin, and tryptophan contents in laser welded porcine aorta tissues studied using fluorescence spectroscopy

The emission spectra from welded and un-welded (normal) porcine aorta tissues were measured on both sides of intima and adventitia layers. A tunable Forsterite laser and a Cr4+: YAG laser with wavelengths of 1250nm, 1455nm and 1460nm were used to weld porcine aorta tissues. Three emission bands emitted from three key fluorophores were studied under different welding and excitation conditions. With excitation wavelength of 340nm, the 395nm band is associated with the emission from the structural proteins of collagen type III and type I. The 445nm band obtained is associated with the emission of the structural protein of elastin. The 350nm band recorded with excitation wavelength of 300nm is associated with the amino acid of tryptophan. The relative emission intensities of collagen, elastin and tryptophan at their fluorescence peaks changes with laser tissue welding wavelengths indicate the change of contents of those tissue molecules. The ratio of emission peak intensities of collagen to elastin with welding laser wavelength of 1250nm increases by 0.13 as compared to the normal aorta tissue at the intimal side. For the adventitial side of aorta tissue, this ratio decreases by 0.38 in comparison with the normal tissue. These results indicate that content of collagen changes relative to elastin due to laser tissue welding. The peak fluorescence intensity of tryptophan for both sides of welded tunica intima and adventitia increases significantly in comparison with the normal tissue when the optimum laser welding wavelength of 1455 nm was used.

UV supercontinuum excitation source generated by SPM and XPM in photonic crystal fibers

The supercontinuum spectrum generated by femtosecond Ti:Sapphire laser in photonic crystal fiber (PCF) can be increased into the UV by using small core diameter PCF with zero dispersion wavelength (ZDW) shorter 600nm. SC is generated in the region 350 to 1200nm with modulation less than 10 dB and with maximum spectral intensity near 350- 450nm. It is further shown that spectral intensity in the UV spectral region can be increased by employing dualwavelength pumping using the second harmonic of Ti:Sapphire laser beam as a second pumping wavelength.

UV extended supercontinuum source for time resolved and steady state spectroscopy for biological and chemical molecules

The spectrum of the supercontinuum generated by a femtosecond Ti:Sapphire laser beam in photonic crystal fiber (PCF) is increased into the UV using small core diameter PCF with zero dispersion wavelength (ZDW) shorter 600 nm. A flat spectrum is generated that spans from 350 to 1000 nm. The SC was used as an excitation source for fluorescence spectroscopy. Fluorescence spectra can be detected from dye molecules, and native molecules in tissues samples with excitation from wavelengths extracted from ultrafast SC light in the spectral range between 350 to 500 nm using narrow bandpass filters. A Streak Camera was used for time-resolved fluorescence measurements.

Ultrashort Lagguere-Gaussian Pulses With Angular and Group Velocity Dispersion Compensation

Coherent optical vortices are generated from ultrashort 6.4 fs pulses with carrier envelope phase control. The properties of angular dispersion and temporal chirp compensated pulses are consistent with a monochromatic Laguerre-Gaussian beam.

Coherence properties of supercontinuum generation in microstructure fiber

Coherence, spectral and temporal properties of the supercontinuum (SC) generation in microstructure fiber were experimentally studied by low peak-power femtosecond pump-pulses propagated in the anomalous and normal dispersion regions.

Supercontinuum multiple frequency channel generation for WDM system

The coherent multiple-frequency channels generation is experimentally demonstrated using two time-delayed, 120 fs pump pulses at 1560 nm. When the pump wavelength is in the anomalous dispersion region far from the zero-dispersion wavelength, stable variable-frequency channels generation using two time delayed pump pulses is achieved.

Spectral, temporal and coherence properties of supercontinuum generation in a photonic crystal fiber

Spectral, temporal and coherence properties of the supercontinuum generation in the photonic fiber were investigated using a novel spectral interferometry approach. It is shown that the coherence is high for the blue-shifted radiation and low for the soliton wavelength region. The multiple channels generation is demonstrated using two time-delayed pulses.