In contrast to paraxial waves, strongly confined light can carry significant transverse spin angular momentum. Here we
report on its direct detection in the evanescent electromagnetic field near the ultrathin waist of an optical nanofiber
waveguide. We demonstrate the spin by its contribution to rotation of an anisotropic microsphere held and spun near the
nanofiber waist by optical tweezers. By setting the driving spin angular momentum in the optical tweezers to be parallel
or antiparallel with respect to the transverse spin near the nanofiber, we can speed up or slow down the particle’s rotation
by about a half of the rotation rate observed without the light in the fiber. We also explore the dependence of this
optomechanical effect on the propagation direction and polarization of the guided light.
Elliptically polarized evanescent electromagnetic fields can exert a transverse optical force on scattering objects immersed in such fields. We demonstrate this experimentally by setting isotropic, dielectric microspheres into orbital motion around a single-mode ultrathin fiber waveguide. In accordance with the theoretical results, the observed orbiting frequency is proportional to the helicity parameter, which is controlled by the degree of circular polarization of the light coupled to the fiber. The microparticles are rotating against the direction of the energy flow circulation around the fiber, thus verifying the theoretically expected negative optical torque. An important prerequisite for the measurements was the complete polarization control for the ultrathin fiber.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.