Spiral interferometry

Abstract

We present a surprising modification of optical interferometry. A so-called spiral phase element in the beam path of a standard microscope results in an interferogram of phase samples, for which the interference fringes have the shape of spirals instead of closed contour lines as in traditional interferograms. This configuration overrides the basic problem of interferometry, i.e., that elevations and depressions cannot be distinguished. Therefore a complete sample profile can be reconstructed from a single exposure, promising, e.g., high-speed metrology with a single laser pulse. The method is easy to implement, it does not require a spatially separated reference beam, and it is optimally stable against environmental noise.

Optical orbital angular momentum

“…The new possibilities offered by these techniques range from the identification of an object against a bright background [40] to omni-edge enhancement [41], the removal of up-down ambiguity in interferometry [42] and probing the properties of an object by separating the orbital angular momentum components of the reflected or transmitted light [43].…”

Orbital angular momentum vertical-cavity surface-emitting lasers

“…Beams carrying OAM are attractive as they offer a theoretically unbounded number of possible states, and have therefore been a subject of great interest for a variety of fundamental and applied research activities at both the classical and the single-photon level. Applications include communication [3], optical manipulation [4], optical microscopy [5], remote sensing [6], and quantum information [7]. Beams with a well-defined state of OAM have a complex field characterized by expilφ, where φ is the azimuthal around the optical axis, and l is the topological charge, an integer describing the number of 2π phase changes around the beam axis.…”

Controllable all-fiber generation/conversion of circularly polarized orbital angular momentum beams using long period fiber gratings

“…As one of the most fundamental physical quantities in classical and quantum electrodynamics, orbital angular momentum (OAM) of light has initiated widespread interest in many areas, including optical tweezers [1], atom manipulation [2][3][4], nanoscale microscopy [5], quantum information processing, and large-capacity optical communication [6][7][8]. A beam of light carrying OAM possesses a phase φ(l,ϕ) = exp(ilϕ) in the transverse plane, where ϕ is the azimuth angle and l is the topological charge number.…”