Generation of a doughnut-shaped beam using a spiral phase plate

Abstract

To generate a doughnut-shaped beam, i.e., the first order of a Bessel beam, a spiral phase plate with 8 divided etching areas is fabricated with an etching accuracy of better than 6 nm. The etching depth of each area is designed so that the phase distribution of the laser beam passing through has a phase difference of π at a symmetric position with respect to the optical axis. Using a laser beam with a wavefront aberration of 1/10λ, the phase distribution of the beam passing through the plate is measured by a Shack Hartman wavefront sensor. It has been found that the beam has a spiral phase change of 2π along the optical axis. The focused beam has a circular doughnut pattern, as predicted by a theoretical calculation, and we succeeded to generate the ideal first-order of a Bessel beam.

Visible-super-resolution infrared microscopy using saturated transient fluorescence detected infrared spectroscopy

“…A pulsed IR laser beam is focused on the sample. The beam of a visible laser is divided into two parts, and a spiral phase plate (SPP) [23] is introduced in one of the arms. The task of the SPP is to create the LG profile of beam Vis1 of Eq.…”

High resolution imaging with differential infrared absorption micro-spectroscopy

“…We further consider that the IR beam is focused on the sample so that it exhibits a node along the optical axis, which is readily made experimentally with a vortex phase plate [45][46][47][48]. A vortex absorption point-spread function (PSF) is then defined by 0, ( , ) ( , )…”

Development of Super-Resolution Microscopy—Application of Laguerre-Gaussian Beam to Microscopy—

“…It is easy to generate a circularly polarized LG beam by passing a linearly one through only a λ/4-plate and a spiral-phase-plate (SPP). In the SPP, the surfaces of the quartz plates are divided into multiple areas spokewise around the center [9]. Each area is etched, so that the optical path length changes stepwise from 0 to λ at a given wavelength.…”

“…The pump (100µW) and erase beams (25mW) were modulated to a light pulse with a width of 20 nsec by two electro-optical modulators. Passing through a λ/4-plate and SPP with 8 etched areas [9], the erase pulse beam was transformed into a circularly polarized 1st-order LG beam. Both beams were co-axially combined and focused onto the micro-beads on a scanning stage by an objective lens.…”