We propose to exploit a self-focusing effect in the atmosphere to assist delivering powerful laser beams from orbit to the ground. We demonstrate through numerical modeling that when the self-focusing length is comparable with the atmosphere height the spot size on the ground can be reduced well below the diffraction limits without beam quality degradation. The density variation suppresses beam filamentation and provides the self-focusing of the beam as a whole. The use of light self-focusing in the atmosphere can greatly relax the requirements for the orbital optics and ground receivers.
[Show abstract][Hide abstract] ABSTRACT: Using the weak nonparaxial approximation, we derive explicit analytical relationships for three projections of the electric field vector of a hypergeometric (HyG) laser beam. For the HyG beams with topological charge n = 0, 1 we derive explicit formulae for the axial intensity, which suggest that the waist position is related to the parameters of the HyG beam and shifted with respect to the plane z = 0. Such a displacement of the axial intensity peak has been given the name 'HyG beam lensless focusing' and formulae for calculating the said shift magnitude (focus distance) are deduced. The propagation of the HyG beam at n = 0 is simulated using the finite-difference time-domain method. The waist shift and the axial intensity magnitudes are shown to agree with those predicted by the approximate relations.
Journal of optics 04/2011; 13(7):075703. DOI:10.1088/2040-8978/13/7/075703 · 2.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We investigate quasi-steady-state (QSS) self-focusing in nonlinear left-handed metamaterials (NL-LHMs) theoretically. We have found that the negative refraction property of LHMs leads to the fact that the changes of the self-focusing distance and the focus appearing time with the spatial-focusing property of the input pulse are contrary to their counterparts for a conventional self-focusing medium. It is further shown that, as the convergence of the input pulse decreases, the first focus appears earlier and corresponds to smaller self-focusing distances, and that the focus moves more slowly at the smallest self-focusing distance, indicating a relatively higher risk of optical damage formation, in sharp contrast with a conventional self-focusing case. Besides, the divergent incidence cases have finite focus moving ranges.
Journal of the Optical Society of America B 11/2009; 26(12):B68-B73. DOI:10.1364/JOSAB.26.000B68 · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The modulation instability (MI) is one of the main factors responsible for the degradation of beam quality in high-power laser systems. The so-called B-integral restriction is commonly used as the criteria for MI control in passive optics devices. For amplifiers the adiabatic model, assuming locally the Bespalov-Talanov expression for MI growth, is commonly used to estimate the destructive impact of the instability. We present here the exact solution of MI development in amplifiers. We determine the parameters which control the effect of MI in amplifiers and calculate the MI growth rate as a function of those parameters. The safety range of operational parameters is presented. The results of the exact calculations are compared with the adiabatic model, and the range of validity of the latest is determined. We demonstrate that for practical situations the adiabatic approximation noticeably overestimates MI. The additional margin of laser system design is quantified.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.