We measure and stabilize the relative angle of (anti-)parallel laser beams to 5 nanoradian per root Hertz resolution by comparing the phases of radio frequency beat notes on a quadrant photodetector. The absolute accuracy is 5.1 microradian and 2.1 microradian for antiparallel and parallel beams, respectively, which is more than 6 and 16 times below the Rayleigh criterion.
This paper quantifies the rate at which laser shot noise energy is delivered to a nanoparticle for the various scenarios commonly encountered in levitated optomechanics. While previous articles have the same form and dependencies, the proportionality constants often differ in the literature. This paper resolves these discrepancies. The rate at which energy is delivered to an optically trapped particle's respective degrees of freedom depends on the radiation pattern of scattered light as well as the direction of laser propagation. For a traveling plane wave with linearly polarized light, in the…
We demonstrate the measurement of nanoparticle shape by angularly resolved Rayleigh scattering of single optical levitated particles that are oriented in space via the trapping light in vacuum. This technique is applied to a range of particle geometries, from perfect spherical nanodroplets to octahedral nanocrystals. We show that this method can resolve shape differences down to a few nanometers and be applied in both low-damping environments, as demonstrated here, and in traditional overdamped fluids used in optical tweezers.
We demonstrate that an ultrashort high intensity laser pulse can propagate for hundreds of Rayleigh ranges in a prepared neutral hydrogen channel by generating its own plasma waveguide as it propagates; the front of the pulse generates a waveguide that confines the rest of the pulse. A wide range of suitable initial index structures will support this "self-waveguiding" process; the necessary feature is that the gas density on axis is a minimum. Here, we demonstrate self-waveguiding of pulses of at least $1.5\times10^{17} W/cm^2$ (normalized vector potential $a_0\sim0.3)$ over 10 cm, or $\sim10…
We present a detailed study of the fields and propagation characteristics around the focus of ultrashort radially-polarized laser beams (RPLBs) having low-order spatio-temporal couplings (STCs). The three STCs considered are the focusing of the different frequencies to different positions along the longitudinal coordinate, the focusing of the frequencies to different positions along one transverse coordinate, and the beam waist or Rayleigh range having a power-law frequency dependence. The STCs considered are deemed low-order because they are generally linear in frequency. The combination of a…
