We present an idea to use optical vortex as a spatial light modulator (SLM) phase modulation depth marker. It can open a way to fast and efficient SLM calibration, which is required especially for SLMs that are able to change between introduced phase shift. Additionally, it may be used to control optical system aberrations and proper SLM phase shift, simultaneously. In this paper, the typical calibration method is discussed in brief. Next the new method based on vortex quality inspection is presented. The idea of the new method is preliminary verified in experiment, which is followed by a discussion of further research, that need to be done.
Optical vortex microscope is an optical system in which the beam illuminating the sample contains the optical vortex- a characteristic structure which contains a point of zero amplitude and undefined phase. Such a beam is very sensitive to the phase or amplitude defects which are introduced into it. In this paper we analyze experimentally the response of the optical vortex microscope to the small phase changes introduced into the beam.
One of the challenges for the Optical Vortex Scanning microscope is to find the effective procedures for surface
topography reconstruction. We proposed an experimental setup to support solution of this problem. The Spatial Light
Modulator (SLM) is used as a phase object. SLM allows to generate phase disturbance in the range 0-2π, which can be
easily introduced into the beam carrying optical vortex. Our system gives an opportunity to measure optical vortex
response due to phase modifications introduced by the SLM and investigate vortex sensitivity. We tested how the object
position, size affects vortex and position of the vortex point inside the beam.
We present the analytical model describing the Gaussian beam propagation through the off axis vortex lens and the set of axially positioned ideal lenses. The model is derived on the base of Fresnel diffraction integral. The model is extended to the case of vortex lens with any topological charge m. We have shown that the Gaussian beam propagation can be represented by function G which depends on four coefficients. When propagating from one lens to another the function holds its form but the coefficient changes.
The optical system working with focused Gaussian beam carrying a higher order optical vortex is considered. Additionally the optical vortex movement inside the beam is proposed allowing the precise scanning of the sample inserted into the beam. The analytical formula for the Fresnel diffraction integral with the shifted optical vortex has been calculated and compared with the numerical results. The experimental validation of this problem has been also presented.
We consider an optical system in which the optical vortex moves inside the focused Gaussian beam. The vortex movement is due to the vortex lens inserted in front of the focusing objective. We gradually shift the vortex lens along the x-axis which is perpendicular to the axis of laser beam propagation (z-axis). This causes that in the image plane vortex moves along a straight line but the line inclination depends on the position of the observation plane. There is a characteristic position of the observation plane, in which the vortex trajectory is perpendicular to the vortex plate shift. We call this plane a critical plane. The critical plane is sensitive to small phase variations which can be introduce by a transparent sample. We propose a way of retrieving the phase profile (at the critical plane) of such a beam. Our procedure is based on the Fourier transform phase demodulation method. We also investigate how the system reacts to the known phase variations introduced into the critical plane.
In this paper we present the Optical Vortex Scanning Microscope (OVSM) in which the new scanning method induced by vortex lens movement is introduced. This method allows to scan the sample in a simple way. The behavior of the vortex position at the sample plane and phase retrieval algorithm is discussed. The new experimental results confirming the progress in the OVSM building are presented.