Fast calculation of the line-spread-function by transversal directions decoupling

Abstract

We propose a simplified method to calculate the optical spread function of a paradigmatic system constituted by a pupil-lens with a line-shaped illumination (‘line-spread-function’). Our approach is based on decoupling the two transversal directions of the beam and treating the propagation by means of the Fourier optics formalism. This requires simpler calculations with respect to the more usual Bessel-function-based method. The model is discussed and compared with standard calculation methods by carrying out computer simulations. The proposed approach is found to be much faster than the Bessel-function-based one (CPU time % of the standard method), while the results of the two methods present a very good mutual agreement.

Practical two‐photon‐absorption cross sections and spectra of eosin and hematoxylin

“…The employed laser source is a mode‐locked Ti:Sapphire (Ti : Al 2 O 3 ) laser (Tsunami, Spectra‐Physics) emitting light pulses of 110 fs at a repetition rate f p of nearly 80 MHz. The illumination line impinging on the sample has a “flat‐top” shape, being 1.18 μm wide in the x direction, with an estimated Rayleigh length of ≃1 μm [38]. The illuminated volume of solution is estimated 1.18 μm × 2 μm × 300 μm ≃ 7.08 × 10 −16 m 3 , that is, ≃708 fl.…”

“…The cuvette has been placed on a microscope slide lying on a suitable micrometric actuator. Further details on the apparatus can be found in [36][37][38][39][40]. The detection setup exploits a Nikon oil-immersion 60× objective with a numerical aperture of 1.4 and a working-distance of '130 μm.…”

Measurement of two‐photon‐absorption spectra through nonlinear fluorescence produced by a line‐shaped excitation beam

“…Our method exploits the phenomenon of two-photon-induced fluorescence emission and belongs to the so-called indirect methods for the TPA detection. The devised technique utilizes a line-shaped illumination to excite the nonlinear fluorescence, with an optical configuration similar to what recently proposed in the nonlinear microscopy domain (Tomaselli et al, 2014;Parravicini et al, 2016). The proposed approach has the advantage to require an optical system being easier than the standard nonlinear fluorescence-based methods.…”

“…The microcuvette has been assembled on a microscope slide, which has been placed on the microscopy actuator. The measurement setup developed by us exploits a two-photon line-excitation-scanning fluorescence microscope developed in our laboratories (Tomaselli et al, 2014;Parravicini et al, 2016). It is equipped with one galvanic silver mirror Galvo-Scanner Thorlabs GVS002 powered by a Galvo-System GPS011, an oil immersion Nikon objective 60×, with a numerical aperture of 1.4, and a working distance of 130 μm.…”

“…The illumination line has a measured width in x direction ('flat-top') of 1.18 μm, with an estimated Rayleigh length of 1 μm (Parravicini et al, 2016). The calculated illuminated volume of solution is therefore 1.18 μm × 2 μm × 300 μm 7.08 × 10 −16 m 3 , i.e.…”