ABSTRACT. This paper discusses the process of light absorption by cold atoms and evaluates the Signal-to-Noise Ratio (SNR). Several noise components are identified and modelled mathematically. The impact of the detector’s effective saturation and optical density on the SNR is analysed, providing insights for optimizing experimental parameters and sensor performance.

ABSTRACT. Based on experimental studies of the physical characteristics of semiconductor materials, the conditions (temperature, concentration of photogenerated minority carriers) required for efficient melting of thin surface layers by pulsed laser action are determined. It is shown that the pulsed laser melting process is athermic in nature and is governed by the concentration of antibonding electron-hole pairs generated by light [1-6]. A hypothesis for low-temperature laser annealing (LA) of semiconductors is proposed, based on the concept of a change in the quantum state of valence electrons affecting a chemical bond. The existence of a critical concentration, ncr, such that the initial state of the semiconductor becomes unstable once the density of antibonding quasi-particles exceeds this value (n>ncr), appears entirely natural. Depending on the experimental conditions — power and duration of LA — low-temperature melting, accelerated diffusion, recrystallization of the amorphous layer, or a structural phase transition to the metallic state, etc., can occur (for Si and GaAs, ncr ≈ 1021 cm-3 and (7–9)·1021cm-3, respectively, were obtained). It is shown that for “melting via the electronic mechanism” to occur, the degree of bond weakening and isotropy must reach a certain critical value. Experimental results are presented demonstrating that, once ncr is reached in shallow semiconductor layers due to light absorption, melting occurs at significantly lower energies than those required to reach the melting temperature by thermal heating alone.