We present direct observation of the velocity-selective optical pumping Rb ground state hyperfine levels induced by 5S(1/2) --> 5P(1/2) femtosecond pulse-train excitation. A modified frequency comb spectroscopy based on fixed and a weak cw scanning probe laser was developed. The excitation Doppler-broadened four-level atomic vapor is investigated theoretically in context density matrix formalism results are compared with experiment.

In this work we investigate operation in the Geiger mode of new single photon avalanche photo diode (SPAD) SAP500 manufactured by Laser Components. This SPAD is sensitive range 400-1000 nm and has a conventional reach-through structure which ensures good quantum efficiency at long end spectrum. By use passive active quenching schemes detection efficiency, timing jitter, dark counts, afterpulsing, gain other important parameters compare them to "standard" low noise C30902SH from Perkin Elmer....

A mode-locked femtosecond laser is used to physically map the frequency comb into velocity of excited Rb atoms at room temperature. Upon resonant excitation by discrete optical frequencies distribution shows comblike structure. Simultaneously, velocity-selective population transfer occurs between ground-state hyperfine levels. Both facts are observed modified direct spectroscopy and verified a detailed density matrix treatment multilevel system in field.

Abstract This study aimed to investigate polymerization kinetics and curing light transmittance of two series experimental dental resin composites filled with 0–40 wt% either 45S5 bioactive glass (BG) or a customized low-Na F-containing BG. Polymerization in 0.1-mm 2-mm thick layers were investigated through real-time degree conversion measurements using Fourier transform infrared (FTIR) spectrometer. FTIR spectra continuously collected at rate 2 s −1 during light-curing (1340 mW/cm ). Light...

We demonstrate a method based on unique sinusoidally shaped phased grating for efficient and nearly alignment free detection of both signs modulus the orbital angular momentum (OAM) light. OAM efficiency is almost same over whole area. The capability robustness this are demonstrated by optical vortices with topological charge up to 150 using reflective phase-only liquid crystal silicon spatial light modulator.

To monitor the real-time changes in light transmittance during composite curing and to use data determine times required for a complete polymerization.Three conventional three bulk fill composites were cured with two light-emitting diode units at layer thicknesses of 2 mm 4 mm. The collected by UV-Vis spectrometer wavelength range 350-550 nm, plotted against time (t) fitted an exponential function f(t), whose first derivative ΔT(t) = df(t)/dt represented rate change. As changing reflects...

A method for determining the topological charge of an optical vortex using off-axis parabolic mirror (OPM) is reported. The results diffraction patterns obtained in reflected focal point OPM show intensity pattern and its orientation depend on as well sign. experimental agree with simulation results. capability robustness this are demonstrated by detection high ±250.

Recording of digital holograms a weak signal [0.44 counts per second (cps)] hidden below the detector's noise (21 cps) is investigated by employing high dynamic range photon-counting detector. conditions are discussed in terms most important holographic measures, namely, fringe visibility (or contrast) and signal-to-noise ratio (SNR), relation to main parameters. Theoretically evaluated curves tested recording for wide parameter values. We found that (i) optimum set parameters can be...

Time-averaged holography has been using photo-emulsions (early stage) and digital photo-sensitive arrays (later) to record holograms. We extend the recording possibilities by utilizing a photon-counting camera, we further investigate possibility of obtaining accurate hologram reconstructions in rather severe experimental conditions. To achieve this, derived an expression for fringe function comprising main parameters affecting recording. Influence parameters, namely exposure time number...

Directed by successfully manufacturing the computer-generated hologram (CGH) using computer-to-film (CtF) process, we present, to best of our knowledge, a new method for low-cost and fast manufacturing. This allows advances in CtF process techniques production. These include computer-to-plate, offset printing, surface engraving utilizing same CGH calculations prepress. With an advantage cost possibility be mass manufactured, aforementioned combined with presented have solid foundation...

Abstract The potential of femtosecond time‐resolved CARS for the determination J ‐dependent line broadening coefficients is demonstrated. With well‐developed technique H 2 Q‐branch ro‐vibrational transitions are measured in pure and + He N mixtures. results show excellent agreement with values obtained by other groups using high‐resolution wavenumber domain. dependence experimental on perturber density also shows good behavior found literature: a linear case hydrogen helium as explicit...

We report on the observation of three RbCs satellite bands in blue and green ranges visible spectrum. Absorption measurements are performed using all-sapphire cell filled with a mixture Rb Cs. compare high resolution absorption spectrum Rb-Cs vapor pure Cs spectra from literature. After detailed analysis, new molecule at 418.3 nm, 468.3, 527.5 nm identified. The origin these is discussed by direct comparison difference potentials derived quantum chemistry calculations potential energy...

To investigate the effects of bleaching agent on microhardness, color and light transmission different restorative materials. Specimens (n=20) Tetric EvoCeram (TEC), Bulk Fill (TECBF) Equia (EQUIA) were treated with either 40% hydrogen peroxide Opalesence Boost or destilled water for 45 min. stained in tea solution stored deionized one two weeks. Color, microhardness monitored at baseline, after immersion storage water. After a significant reduction surface (p<0.001) was recorded all...

Abstract Femtosecond time‐resolved degenerate four‐wave mixing (DFWM) spectroscopy with ultrashort laser pulses was applied to probe pure rotational Raman transitions of the H 2 molecule. Owing broad bandwidth sub‐20 fs pulse, several Stokes and anti‐Stokes are simultaneously excited same making experiment relevant for thermometry in combustion processes. Simulations DFWM signal accurately predict how change population distribution due changes temperature influences shape transients...

We investigated the coherence accumulation in Rb atoms excited by a train of femtosecond pulses. The results velocity selective optical pumping hyperfine levels, observed cw probe laser. effects pulse excitation on laser transmission were investigated, depending power. absorption increase strong case, followed reduction modulations absorption. Results show that population and can be effectively reduced eventually destroyed increasing intensity. A therefore serve as switch from pulse-train to...

We studied the emission from dense rubidium vapor under 100-fs pulsed laser excitation in 730--820 nm range. Self-focusing along with a conical (CE) was observed for blue wing of $D2$ atomic resonance. Self-defocusing occurred red-wing excitation. This is accordance theory intensity dependent nonlinear refraction index. In case CE observation, our experimental results are attributed to self-phase modulation beam interacting near-resonant medium.

In time-averaged digital holography (TADH), one records a hologram of periodically oscillating object by using the exposure time typically much longer than period. Problems arise when total available is restricted or oscillation period unknown. this work we investigate effects short to quality recorded and show that, record high fidelity information in shortest possible time, close estimates phase are required. To that end propose an advanced procedure based on exposures allows obtaining...