Physics

The cavernous nerves (CN) course along the prostate surface and are responsible for sexual function. Optical nerve stimulation (ONS) has recently been tested as a potential alternative to electrical nerve stimulation for identifying and preserving these delicate nerves during prostate cancer surgery. However, the optimal range of laser parameters for safe and consistent laser nerve stimulation is relatively narrow; low-level irradiation may not stimulate the nerve, while high-level irradiation may result in thermal damage to the nerve and loss of erectile function. The objective of this study is to design, build, and provide preliminary data on testing of a laparoscopic probe capable of delivering a collimated, flat-top spatial beam profile to the nerve surface for uniform, safe, and reproducible irradiation of the nerve. Chemical etching of the distal fiber optic tip in combination with an aspheric lens resulted in a 3.4-mm-OD laparoscopic probe capable of delivering a collimated 1-mm-diameter, flat-top laser beam over a working distance of about 20 mm. Successful ONS using this probe was observed in a rat prostate model, in vivo. Upon further testing, this probe may be useful for identifying and preserving the CN during laparoscopic nerve-sparing prostate cancer surgery.

Successful identification and preservation of the cavernous nerves (CN), which are responsible for sexual function and vulnerable to damage during prostate cancer surgery, will require subsurface detection of the CN's beneath a thin fascia layer. This study explores the feasibility of optical nerve stimulation (ONS) in the rat with a fascia layer placed over the CN. Two near-infrared diode lasers with wavelengths of 1455 and 1550 nm were operated in continuous-wave mode for stimulation of the CN in 8 rats, in vivo. Successful ONS was confirmed by an intracavernous pressure (ICP) response in the rat penis at 1455 nm through fascia with a thickness up to 110 μm and at 1550 nm through fascia with a thickness up to 450 μm. Higher incident laser power was required to produce an ICP response as fascia thickness was increased. Also, weaker and slower ICP responses were observed as fascia thickness was increased. Subsurface ONS of the rat CN at a depth of 450 μm using a 1550 nm laser i...

Optical-domain subsampling enables Fourier-domain OCT imaging at high-speeds and extended depth ranges while limiting the required acquisition bandwidth. To perform optical-domain subsampling, a wavelength-stepped rather than a wavelength-swept source is required. This preliminary study introduces a novel design for a rapid wavelength-stepped laser source that uses dispersive fibers in combination with a fast lithiumniobate modulator to achieve wavelength selection. A laser with 200 GHz wavelength-stepping and a sweep rate of 9 MHz over a 94 nm range at a center wavelength of 1550 nm is demonstrated. A reconfiguration of this source design to a continuous wavelength-swept light for conventional Fourier-domain OCT is also demonstrated. , "High-speed wavelength-swept semiconductor laser with a polygon-scanner-based wavelength filter," Opt. , 1981-1983 (2003), http://www.opticsinfobase.org/ol/abstract.cfm?id=74886. 2. W. Y. Oh, B. J. Vakoc, M. Shishkov, G. J. Tearney, and B. E. Bouma, ">400 kHz repetition rate wavelengthswept laser and application to high-speed optical frequency domain imaging," Opt. Lett. 35(17), 2919-2921 (2010), http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-35-17-2919. 3. R. Huber, M. Wojtkowski, and J. G. Fujimoto, "Fourier domain mode locking (FDML): A new laser operating regime and applications for optical coherence tomography," Opt.

Abstract Herein, we present vibronic excitation and detection of purely electronic zero-phonon lines (ZPL) of single molecules as a new tool for investigating dynamics at cryogenic temperatures. Applications of this technique to study crystalline and amorphous matrix materials are presented. In the crystalline environment, spectrally stable ZPLs are observed at moderate excitation powers.

Optofluidic components enable flexible routing and transformations of light beams in integrated lab-on-a-chip systems with the use of carefully shaped fluid parcels. For structural integrity reasons, the working fluid is typically contained within a solid-material chip. One of the outstanding challenges in optofluidics is the preparation and processing of optofluidic waveguides.

We report measurements of ultrahigh quality factors (Q-factors) of the optical whispering-gallery modes excited via a tapered optical-fiber waveguide in single glycerol–water microdroplets standing on a superhydrophobic surface in air. Owing to the high contact angle of the glycerol–water mixture on the superhydrophobic surface (> 155°), microdroplets with the geometry of a truncated sphere minimally distorted by gravity and contact line pinning effects could be generated.

Abstract We report optically pumped continuous-wave lasing from self-assembled InAs and InGaAs quantum dots (QDs) embedded in high-quality-factor microdisk laser structures. The microdisk emission spectra show lasing on 1–5 well separated modes in the wavelength range between 900 and 990 nm. The estimated threshold pump densities are between 20 and 200 W/cm 2. The lasing characteristics are discussed in terms of both inhomogeneously and homogeneously broadened QD transitions.© 2000 American Institute of Physics.

A fully reversible photothermal tuning of an inorganic salt (NaCl)–water microdroplet standing on a superhydrophobic surface is demonstrated. The size change of the microdroplet is caused by a focused infrared laser beam in a humidity-controlled chamber and a fully reversible large spectral tuning up to B40 nm is achieved.

Abstract We demonstrate large spectral tuning of glycerol/water microdroplets standing on a superhydrophobic surface using the optical scattering force exerted by a 1064 nm Nd 3+: YVO 4 solid-state laser. Spectral tuning up to 30 nm is presented in the whispering gallery modes as a result of the deformation of the microdroplets toward a truncated prolate spheroid geometry. Observed large spectral tuning is also reported to be highly reversible.

We demonstrate vibronic excitation combined with spectrally resolved zero phonon line detection of single terrylenediimide (TDI) molecules in both the Shpol'skii matrix hexadecane and the polymer PMMA at cryogenic temperatures. Spectral jumps as large as are recorded with a 1 s time resolution. This technique does not require a weak electron–phonon coupling, and promises applications in spectroscopy of a wide-range of single nanostructures in amorphous hosts including fluorescing proteins.

Abstract We demonstrate, for the first time to our knowledge, Raman lasing from stationary microdroplets on a superhydrophobic surface. In the experiments, glycerol–water microdroplets with radii in the 11–15 μ m range were pumped at 532 nm with a pulsed, frequency-doubled Nd: YAG laser. Two distinct operation regimes of the microdroplets were observed: cavity-enhanced Raman scattering and Raman lasing. In the latter case, the Raman lasing signal was higher than the background by more than 30 dB.

We demonstrate heralded single photon emission from a self-assembled InAs quantum dot (QD). Pulsed optical excitation (82 MHz) together with Coulomb renormalization effects allows for the realization of regular single photon emission at the excitonic transiton (1X) with nearly 100% efficiency. By temperature tuning, we are able to shift the 1X transition into resonance with a whispering gallery mode of a microdisk (Q∼ 6500) and achieve turnstile operation of the coupled QD-cavity system.

We characterized room-temperature fluorescence properties of single terrylene molecules embedded in anthracene thin films that were prepared by spin-coating on glass substrates. Our results show that terrylene molecules embedded in anthracene matrix are oriented nearly parallel to the substrate. Typical measured fluorescence lifetime of terrylene was 3.6 ns and photon count rate at saturation was 750kHz.

A self-stabilization mechanism locking the size of single inorganic salt (NaCl)–water microdroplets that are standing on a superhydrophobic surface and kept in a humidity-controlled chamber is demonstrated. The effect is based on the hysteretic behavior of a photothermal tuning cycle caused by the whispering gallery mode (WGM) absorption resonances that are observed when scanning the power of an infrared laser focused at the rim of a microdroplet.

Two photons which are sent to two different input channels of a 50/50 beam-splitter will interfere depending on their indistinguishability. Ideally indistinguishable photons will exhibit the bunching behavior, ie they will leave the beam splitter through the same output channel [1]. Apart from being a major demonstration of the quantum theory of light, this phenomenon has so far proven to be very suitable for applications in quantum information science.

Optical microcavities [1] promise important applications in optical communication systems based on wavelength division multiplexing as optical switches and add/drop filters. Various demonstrations have been performed using semiconductor or polymer microdisk and microring microcavities [2]. However, despite the inherent potential, microcavity based devices have not found wide use in modern optoelectronic networks. One of the main obstacles has been tunability.

Abstract. Glycerol/water microdroplets take almost spherical shapes when standing on a superhydrophobic surface. Hence they are suitable to function as optical microcavities. Using Rhodamine B doped water microdroplets, large spectral tunability of the whispering gallery modes (WGMs)(> 5 nm) was observed. Tunability was achieved by evaporation/condensation in a current controlled mini humidity chamber. Experiments revealed a mechanism stabilizing the volume of these microdroplets with femtoliter resolution.