Charlotte Stahl

Complete representation of a correlation singularity in a partially coherent beam.

An understanding of phase singularities of correlation functions is important in optical coherence theory and imaging science, but to date such singularities have only been theoretically studied in a single transverse plane, at most. In this Letter we evaluate the complete structure of a correlation singularity of a partially coherent Laguerre-Gauss beam, describing it in both the transverse and the propagation directions. These results agree with previously found solutions, and introduce new aspects of correlation singularities.

Partially coherent vortex beams of arbitrary order

We derive analytic solutions for an infinite set of partially coherent vortex beams (PCVBs) of any azimuthal order and for any propagation distance. The correlation singularities of the beams and their orbital angular momentum are investigated. This detailed study of PCVBs opens the possibility of using such beams for remote sensing and free-space optical communications.

Analytic calculation of vortex diffraction by a triangular aperture

We present an analytic calculation of the diffraction of a vortex beam by a triangular aperture. This calculation is used to study the diffraction of multimode vortex beams and off-axis vortex beams. Implications of these results for the effectiveness of diffraction as a vortex detection method are discussed.

Comparison of three pulsed infrared lasers for optical stimulation of the rat prostate cavernous nerves

Optical nerve stimulation (ONS) is being explored for identification and preservation of the cavernous nerves (CN), responsible for erectile function, during prostate cancer surgery. This study compares three pulsed infrared lasers to determine whether differences in spectral linewidth and/or temporal pulse profile influence successful ONS of CN. Infrared laser radiation from the Capella diode laser (1873 nm, 5 ms, 10 Hz), Thulium fiber laser (TFL) (1873 nm, 5 ms, 10 Hz), and solid-state Holmium:YAG laser (2120 nm, 200 μs, 5 Hz) were transmitted through 400-μm-corediameter optical fibers, producing a 1-mm-diameter-spot on the nerve surface. Successful ONS was judged by an intracavernous pressure (ICP) response in the penis (n =10 rats) during a total stimulation time of 30 s. The narrow linewidth TFL (Δλ ~ 0.5 nm) and broad linewidth Capella laser (Δλ ~ 12 nm) performed similarly, producing ICP responses with a threshold radiant exposure of ~ 0.45 J/cm2, and ICP response times of 12-17 s, while the Holmium laser stimulated at ~ 0.59 J/cm2, and ICP response times of about 14-28 s. All three lasers demonstrated successful ONS of CN. ICP response time was dependent on the rate of energy deposition into the CN, rather than linewidth or temporal pulse profile.

Subsurface optical stimulation of rat prostate cavernous nerves using a continuous wave, single mode, 1490 nm diode laser

Successful identification of the cavernous nerves (CN’s) during radical prostatectomy requires detection of the CN’s through a thin layer of overlying fascia. This study explores the 1490 nm infrared (IR) diode laser wavelength for rapid and deep subsurface CN stimulation in a rat model, in vivo. A 150-mW, 1490-nm diode laser providing an optical penetration depth of ~ 520 μm was used to stimulate the CN’s in 8 rats through a single mode fiber optic probe with 1-mm-diameter spot and 15 s irradiation time. Successful ONS was judged by an intracavernous pressure response (ICP) in the rat penis. Subsurface ONS at 1490 nm was also compared with previous studies using 1455 and 1550 nm IR diode laser wavelengths. ONS was observed through fascia layers up to 380 μm thick using an incident laser power of ~ 50 mW. ICP response times as short as 4.6 ± 0.2 s were recorded using higher laser powers bust still below the nerve damage threshold. The 1490-nm diode laser represents a compact, low cost, high power, and high quality infrared light source for use in ONS. This wavelength provides deeper optical penetration than 1455 nm and more rapid and efficient nerve stimulation than 1550 nm.