Using methods of pulsed laser ablation from a silicon target in helium (He)-nitrogen (N2) gas mixtures maintained at reduced pressures (0.5–5 Torr), we fabricated substrate-supported silicon (Si) nanocrystal-based films exhibiting a strong photoluminescence (PL) emission, which depended on the He/N2 ratio. We show that, in the case of ablation in pure He gas, Si nanocrystals exhibit PL bands centered in the “red - near infrared” (maximum at 760 nm) and “green” (centered at 550 nm) spectral regions, which can be attributed to quantum-confined excitonic states in small Si nanocrystals and to local electronic states in amorphous silicon suboxide (a-SiOx) coating, respectively, while the addition of N2 leads to the generation of an intense “green-yellow” PL band centered at 580 nm. The origin of the latter band is attributed to a radiative recombination in amorphous oxynitride (a-SiNxOy) coating of Si nanocrystals. PL transients of Si nanocrystals with SiOx and a-SiNxOy coatings demonstrate nonexponential decays in the micro- and submicrosecond time scales with rates depending on nitrogen content in the mixture. After milling by ultrasound and dispersing in water, Si nanocrystals can be used as efficient non-toxic markers for bioimaging, while the observed spectral tailoring effect makes possible an adjustment of the PL emission of such markers to a concrete bioimaging task.
Experimental results on 1D and 2D phase-locking of laser diode arrays are presented. Attention is paid to the employment of the arrays consisting of wide aperture lasers diodes. Selection of the "in-phase" supermode, preferable for most of the cases, is attained in the external quarter Talbot (Lc=ZT/4=d 2 /2l) cavity due to the output mirror tilt at the angle jm=l/2d. Analysis of the parameters that influence on the phase-locking is given. Our experiments confirm theoretical predictions of the system stability and adequate selectivity for the laser diode array fill factor (FF) FF=0.6.
We derive the general formula, at a finite cutoff, for the change in the boundary condition of a scalar field in AdS under a Multiple-trace deformation of the dual CFT. Our analysis suggests that fluctuations around the classical solution in AdS should not be constrained by boundary conditions.
The overview of the phase-locking technique is presented. Analysis of the parameters that influence on the phaselocking is given. Admissible range of the deviation of the linear laser diode array, external cavity parameters is estimated. Comparison of the external Talbot cavity configuration with the other ones is held. Attention is paid to both investigation and employment of the laser diode arrays consisting of wide aperture lasers that opens an avenue to high power output radiation in a phase-locked mode. Special consideration is given to the cavity supermodes selection.Our experiments both confirm actual feasibility of 1D and 2D phase-locking of LDA's with specified parameters in the external Talbot (LC=ZT/4) cavity and illustrate theoretical predictions ofthe system stability and selectivity, so that:. phase-locking in 1D configuration allowed difractional limited lobes width W=O.5 mrad;. tiltingof the output mirror provided "in-phase" supermode selection;. phase-locking in 2D configuration of the two LDA's of N=8 lasers, separated by 1600 mkm resulted in diffractional lobes full width at halfmaximum '=O.5 mrad in slow axis and 8'3!=O.25 mrad in fast axis.
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