D. V. Yakovlev

Spectral Characteristics of Subcritical Carbon Dioxide in Nanopores

Coherent anti-Stokes Raman scattering spectra measured within the Q-branch of the vibrational transition ν1 are used to gain insights into the state of carbon dioxide molecules in nanopores of Vycor™ glass at room temperature (20.5°C) and a subcritical temperature of 30.5°C and gas pressures up to the saturation point Psat for each temperature. Along with the main spectral component, belonging to gaseous CO2 molecules, the spectra recorded at pressures close to Psat feature a second (low-frequency) component. The second component is associated with the contribution from the CO2 molecules trapped inside pores. A spectral deconvolution with account for the interference of these two bands makes it possible to estimate the spectral characteristics of the second (low-frequency) component at each temperature. At 20.5°C, the bandwidth of the low-frequency component decreases with CO2 pressure, a behavior that can be explained by the transition of CO2 from the adsorbed to the condensed state in the pore. At the subcritical temperature of 30.5°C, the spectral width of the second component is pressure-independent and close to the value measured in the bulk of the supercritical fluid, a result likely associated with a low-temperature shift of the critical point of the substance trapped in nanopores.

Parametric amplification of broadband radiation of a cw superluminescent diode under picosecond pumping

It is proposed to use cw superluminescent diodes with a spectral width of about 300 and high spatial coherence as seed radiation sources in parametric amplifiers with picosecond pumping in order to form broadband picosecond pulses. A two-cascade parametric amplifier based on (BBO) crystals is pumped by pulses of the second harmonic of an Nd : YAG laser. For a superluminescent diode spectral width of (centre wavelength ), the spectral width of picosecond pulses at the parametric amplifier output is . At a total pump energy of for BBO crystals, the energy of the enhanced emission of the superluminescent diode is found to be .

Application of optoelectronic negative feedback to ordering of the temporal structure of the diode-pumped Nd:YLF laser radiation

The conditions of the generation of radiation with ordered temporal structure are determined for a solid-state laser with external negative feedback. Experiments are performed based on the Nd:YLF laser longitudinally pumped by a high-power diode array. Lasing was controlled using an intracavity electro-optic modulator based on a lithium tantalate crystal. Intensity smoothing and self-mode-locking regimes with generation of several short pulses in the axial interval are implemented by varying the delay in the feedback circuit. Under conditions of amplification above the stability boundary, the secondary electro-optic effect manifestation was detected in the lithium tantalate crystal.

Precise synchronization of qcw pumped active-passive mode locked picosecond lasers

We present designing qcw diode pumped Nd:YAG picosecond laser with 50 ps jitter of output pulse relative to active mode locking signal. Adjustment of signal delay in negative feedback circuit provides generation of transform-limited laser pulses. Obtained level of jitter is mainly attributed to phase noise of radio-frequency active mode locking signal generator. Further jitter decrease by means of enhancement of radio-frequency signal filtering and suppressing of phase noise is discussed.

Thermolens manifestation in end-pumped picosecond Nd:YAG laser

Experimental and theoretical modeling results for pulsed diode-array end-pumped Nd:YAG laser with aberrational thermolens are presented. Millijoule level energy stable picosecond pulse generation is realized in a wide range of repetition rates. Limiting factors of stable laser operation and quantitative contribution of aberrations in beam quality degradation are discussed.

High-resolution spectroscopy of inhomogeneously broadened Raman resonances by time-domain CARS

Time-domain technique was used for experimental investigation of narrow molecular resonances of H2 and CO2 with total width about 10-2-10-3 cm-1 and with spectral shape profile governed by several physical mechanisms. Experimental pulse response were measured in delay time range up to 16 ns. Qualitative and of numerical analysis of the results will be discussed.