Generating autofocused aberration laser beams with different spectral performance

Abstract

We present a flexible approach for generating autofocused aberration laser beams (ALBs) of different wavelengths based on the diffractive optical element (DOE) design with distinct phase transmittance that has radial power q and periodic angular dependence sin(mφ). The diffraction pattern of ALBs strongly depends on the periodic angular power controlled phase of the DOE. During free-space propagation, the ALBs with different wavelengths convert into different light distributions that have mth-order symmetry (for odd m) and 2mth-order symmetry (for even m). The ALBs exhibit autofocusing properties that significantly differ at longer wavelengths relatively with smaller wavelengths. The formation of light intensity distributions in free-space propagation has a sharp focusing feature that strongly depends on the radial power q. The numerically simulated results are presented for wavelengths in the infrared, visible, and ultra-violet regimes. The experimental findings measured at a wavelength of λ = 1064 nm, show good agreement with the numerically simulated results and thus verifying our approach.

Generating asymmetric aberration laser beams with controlled intensity distribution

“…The asymmetry induced variation in the intensity distribution has also been observed with other beams such as LG, Bessel, Bessel-Gauss and Kummer laser beams [47][48][49][50][51]. For an ideal ALB, the relationship between the beam parameters and auto-focusing distance is given as [34]…”

“…The diffractive version of such a phase element will be equivalent to a classical lens (quadratic phase dependence) [33]. As pointed by earlier studies [34,35], the ALB shows more abrupt focusing for q = 2, therefore in the present work the numerical simulations and experiment are performed for q = 2. However, for other values of q a general expression of aALB has been provided in Appendix A.…”

“…It has been shown that for q > 1, ALBs possess an abrupt auto-focusing. The spectral dependence of auto-focusing of ALBs has also been studied, indicating that auto-focusing distance decreases with the increase in wavelength [34]. A study on the robustness of propagation of ALBs in a disorder media has been performed, and several special characteristics such as good self-healing abilities, invariance of auto-focusing distance on disorder strength, controlled variation of auto-focusing distance from a small to large values, have been observed [35].…”

Generating asymmetric aberration laser beams with controlled intensity distribution

“…It has been shown that for q > 1, ALBs possess an abrupt autofocusing. The spectral dependence of ALBs showed that longer wavelength possesses shorter autofocusing distance [43]. The ALBs are also found to be turbulence resilient [24].…”

“…In ALBs, the autofocusing enables to obtain high-power density focused spot, but spatially it always occurs at the center of the beam, irrespective of parameters of ALB [23,24,43].…”