9 research outputs found
Structuring Light for Investigating Optical Vortices
Vortices are well known in our world: tornadoes, hurricanes, and quickly stirred iced tea all demonstrate the vortex phenomenon. In addition to these classical fluids, vortices exist in laser light. While classical fluid vortex dynamics is one of the oldest studied physics problems, the study of optical vortices is only a few decades old. Paralleling the community’s curiosity of quantized vortices in quantum fluids, such as super fluid helium and Bose-Einstein condensate, there is immense interest in the study of optical vortices. In this article, we cover the basic theory of structuring light to generate optical vortices and then discuss experiments performed to study their characteristics and dynamics
Quantized Optical Vortex-array Eigenstates in a Rotating Frame
Linear combinations of Bessel beams can be used to effectively trap light
within cylindrical domains. Such hard traps can be used to produce states that
exhibit stationary arrays of optical vortices from the perspective of a
steadily rotating frame. These patterned singularities can be engineered to
have singularities of the same or mixed charges and the requisite rotation
rates are quantized even though the setting is purely linear. A hydrodynamic
interpretation is that the vortices are at rest within a compressible,
two-dimensional fluid of light
The Anatomy of Geometric Phase for an Optical Vortex Transiting a Lens
We present an analytical means of quantifying the fractional accumulation of
geometric phase for an optical vortex transiting a cylindrical lens. The
standard fiber bundle of a Sphere of Modes is endowed with a Supplementary
Product Space at each point so that the beam waists and their positions can be
explicitly tracked as functions of lens transit fraction. The method is applied
to quantify the accumulation of geometric phase across a single lens as a
function of initial state and lens position within the beam. It can be readily
applied to a series of lenses as well.Comment: 10 pages, 13 figure
Pump-tailored Alternative Bell State Generation in the First-Order Hermite-Gaussian basis
We demonstrate entangled-state swapping, within the Hermite-Gaussian basis of
first-order modes, directly from the process of spontaneous parametric
down-conversion within a nonlinear crystal. The method works by explicitly
tailoring the spatial structure of the pump photon such that it resembles the
product of the desired entangled spatial modes exiting the crystal.
Importantly, the result is an entangled state of balanced HG modes, which may
be beneficial in applications that depend on symmetric accumulations of
geometric phase through optics or in applications of quantum sensing and
imaging with azimuthal sensitivity. Furthermore, the methods are readily
adaptable to other spatial mode bases
Initial Optical Vortex Amplitude Structure Determines Pair Annihilation
We show that annihilation dynamics between oppositely charged optical vortex
pairs can be manipulated by modifying only the initial size of the vortex
cores. When sufficiently close together, vortices with strongly overlapped
cores annihilate more quickly than vortices with smaller cores that must wait
for diffraction to cause meaningful core overlap. We present numerical
simulations and experimental measurements for vortices with hyperbolic tangent
cores of various initial sizes. We also show that decreasing the core size of
an annihilating pair can prevent the annihilation event
Experimental measurement of the geometric phase of non-geodesic circles
We present and implement a method for the experimental measurement of
geometric phase of non-geodesic (small) circles on any SU(2) parameter space.
This phase is measured by subtracting the dynamic phase contribution from the
total phase accumulated. Our design does not require theoretical anticipation
of this dynamic phase value and the methods are generally applicable to any
system accessible to interferometric and projection measurements. Experimental
implementations are presented for two settings: (1) the sphere of modes of
orbital angular momentum, and (2) the Poincar\'e sphere of polarizations of
Gaussian beams
Characterizing Vortex Beams from a Spatial Light Modulator with Collinear Phase-shifting Holography
We demonstrate collinear phase-shifting holography for measuring complex optical modes of twisted light beams with orbital angular momentum (OAM) generated by passing a laser through a spatial light modulator (SLM). This technique measures the mode along the direction of propagation from the SLM and requires no additional optics, so it can be used to aid alignment of the SLM, to efficiently check for the effects of beam wander, and to fully characterize generated beams before use in other experiments. Optimized error analysis and careful SLM alignment allow us to generate and measure OAM with purity as high as 99.9%