Search

A Gaussian-wave theory is developed for the classical and quantum analysis of the z-scan method that is often used to measure third-order nonlinearities. The theory allows us to compute the transmittance in the z scan and the associated regimes of amplitude squeezing. The classical limits of our theory are in perfect agreement with the previous theoretical results. We show that amplitude squeezing of 1.2dB can be obtained using the z scan with a careful selection of the signal power and the aperture size.

We present a quantum theory of nondegenerate phase-sensitive parametric amplification in a χ(3)nonlinear medium. The nonzero response time of the Kerr (χ(3)) nonlinearity determines the quantum-limited noise figure of χ(3)parametric amplification, as well as the limit on quadrature squeezing. This nonzero response time of the nonlinearity requires coupling of the parametric process to a molecular vibration phonon bath, causing the addition of excess noise through spontaneous Raman scattering. We present analytical expressions for the quantum-limited noise figure of frequency nondegenerate and frequency degenerate χ(3)parametric amplifiers operated as phase-sensitive amplifiers. We also present results for frequency nondegenerate quadrature squeezing. We show that our nondegenerate squeezing theory agrees with the degenerate squeezing theory of Boivin and Shapiro as degeneracy is approached. We have also included the effect of linear loss on the phase-sensitive process.

We present a quantum theory of nondegenerate phase-sensitive parametric amplification in a χ^(3) nonlinear medium. The nonzero response time of the Kerr (χ^(3)) nonlinearity determines the quantum-limited noise figure of χ^(3) parametric amplification, as well as the limit on quadrature squeezing. This nonzero response time of the nonlinearity requires coupling of the parametric process to a molecular vibration phonon bath, causing the addition of excess noise through spontaneous Raman scattering. We present analytical expressions for the quantum-limited noise figure of frequency nondegenerate and frequency degenerate χ^(3) parametric amplifiers operated as phase-sensitive amplifiers. We also present results for frequency nondegenerate quadrature squeezing. We show that our nondegenerate squeezing theory agrees with the degenerate squeezing theory of Boivin and Shapiro as degeneracy is approached. We have also included the effect of linear loss on the phase-sensitive process.

We investigate the generation of amplitude-squeezed states with degenerate optical parametric amplifiers that are pumped by focused Gaussian beams. We present a model that facilitates the calculation of the squeezing level for an experimentally realistic configuration in which there is a Gaussian input signal beam that has the same confocal parameter and waist location as the Gaussian pump beam, with no restriction on the interaction length-to-confocal parameter ratio. We show that the 3-dB squeezing limit that was thought to be imposed by the Gaussian pump profile can be exceeded in the (previously uninvestigated) tight-focusing regime. We find the maximum possible amplitude squeezing in this regime to be 4.65 dB. However, it is possible to increase the squeezing level further by spatially filtering the tails of the output signal beam, resulting in squeezing levels in excess of 10 dB.

We report a synchronously pumped optical parametric oscillator that generates the sum frequency of the pump and the signal wavelengths. A single KTiOPO_4 (KTP) crystal is used for both parametric generation and sum-frequency generation in which these two processes are simultaneously phase matched for the same direction of propagation. The parametric oscillator, pumped by a femtosecond Ti:sapphire laser at a wavelength of 827 nm, generates a blue output beam at 487 nm with 43% power-conversion efficiency. The polarization geometry of simultaneous phase matching requires rotation of the pump polarization before the cavity. Adjusting the group delay between the two orthogonally polarized pump components to compensate for the group-velocity mismatch in the KTP crystal increases the photon-conversion efficiency more than threefold. Angle tuning in conjunction with pump wavelength tuning provides output tunability in the 484–512-nm range. A plane-wave model that takes group-velocity mismatch into account is in good agreement with our experimental results.

Zusammenfassung: Problemstellung: In der vorliegenden Arbeit wurde eine faltbare bikonvexe hydrophile „one-piece“ Acryllinse 6 Monate nach Implantation überprüft. Patienten und Methode: In dieser Studie wurde 30 Kataraktpatienten eine hydrophile „one-piece“ Corneal Acrygel® Intraokularlinse nach Phakoemulsifikation durch eine temporale 3.2 mm Clear-Corneal-Incision mittels Implantationspinzette implantiert. Die Operationsmethode und das postoperative Management waren standardisiert. Alle Operationen wurden von einem erfahrenen Chirurgen durchgeführt. Die postoperative Inflammation wurde mit dem Laser-Flare-Cellmeter KOWA FC-1000 am 1., 3., 7., 28. Tag und nach 6 Monaten in dilatiertem Zustand gemessen. Die biomikroskopische Untersuchung erfasste semiquantitativ die Zentrierung und die vordere und hintere Linsenkapselmorphologie. Weiters wurden der bestkorrigierte Visus und der Augendruck erhoben. Ergebnisse: Die Tyndallometrie ergab einen postoperativen Anstieg der Messwerte bis zur ersten Woche postoperativ, um nach 6 Monaten wieder auf annähernd präoperative Werte zu sinken. Die Linse war in allen Fällen gut zentriert. In 86,3% beobachten wir eine Fibrose des Rhexisrandes, wobei sie in 52,6% nur Grad 1 von 4 erreichte. Ein Vorwachsen von Linsenepithelzellen auf die Linsenvorderfläche fand sich in 77,2% aller Augen. In 36,3% beobachteten wir Spannfalten im Bereich der hinteren Kapsel und eine minimale regeneratorische Nachstarrate in 72,7%. Einen bestkorrigierten Visus über 6/12 erreichten alle Patienten. Komplikationen, insbesondere ein Druckanstieg oder Fibrinreaktionen, konnten nicht beobachtet werden. Diskussion: Die Linse weist gute Biokompatibilität und gutes Zentrierungsverhalten auf. Das Haptikdesign und das Linsenmaterial mögen für die Form der Regeneratbildung auf der hinteren Kapsel verantwortlich sein. Summary: Purpose: To describe a foldable biconvex hydrophilic „one-piece“ acrylic intraocular lens 6 month after implantation. Patients and methods: Thirty patients were included for this study. The operation method and the postoperative therapy were standardized. Photometric measurements with the laser-flare-cell-meter KOWA FC-1000 were performed on day before the operation, on the 1st, 3rd, 7th, 14th, 28th day and 6 month after surgery. Cellular reactions on the anterior and posterior capsule as well as centration of the lens were examined by using a slitlamp. Visual acuity and intraocular pressure were performed in all cases. Results: Flare values increased on the first postoperative days and successively decreased on the following days. Centration of the lens was satisfactory. A low degree of fibrosis on the anterior capsular rim occured in 86,3% of all cases. Lens epithel cells on the anterior optic surface could be found in 77,2% of the cases. Folds in the posterior capsule were demonstrated in 36,3% and a low degree of posterior capsule opacification was seen in 72,7% of all eyes. All patients reached best corrected visual acuity 6/12 or better. At no time we observed complications such as an increase of intraocular pressure or fibrin reactions. Discussion: This lens shows a good biokompatibility. Clinically results are satisfactory. Type of regeneration on the posterior capsule might be the results of haptic-design and lense material.

DifferentialUBV observations of the small amplitude (0.12 mag inV) single-lined active binary V350 Lac are presented. It was observed that the light minima occur in conjunction time. A shift of the light curve (0.05 in orbital phase) towards lower phases could be due to a small error in the light elements. The primary minimum is about 0.04 mag deeper than the secondary. It was shown that different depths of two light minima are not produced by the reflection effect but due primarily to gravity darkening on the tidally elongated and synchronously rotating visible component. An O'Connel effect observed as the brighter primary maximum could be an indication of starspot activity or gas streaming between the components.

Using spontaneous optical parametric downconversion, we experimentally demonstrate heralded generation of shaped single photons, whose modes are tailored indirectly by applying amplitude modulation on the pump field that drives the downconversion process. Our experiment opens a door to creating high-quality, mode-shaped single photons at a substantially higher efficiency than is possible with the existing method of direct single-photon shaping.

Abstract Abstract An hepatomesenteric trunk, formed by the common hepatic and superior mesenteric arteries, was found in a 50-year-old male cadaver. The left gastric and splenic arteries arose as a common trunk, the gastrosplenic trunk, from the abdominal aorta; no typical celiac trunk was present. In addition, the hepatomesenteric trunk passed posterior to the portal vein. A knowledge of variations of the common hepatic artery may be important in pancreaticoduodenectomy, as well as during hepatic artery infusion chemotherapy.

We report a synchronously pumped intracavity frequency-doubled optical parametric oscillator that employs a single KTiOPO_4 crystal for both parametric generation and frequency doubling. Both nonlinear processes are phase matched for the same direction of propagation in the crystal. The parametric oscillator, pumped by a femtosecond Ti:sapphire laser at a wavelength of 745??nm, generates a green output beam at 540??nm with a 29% power conversion efficiency. Angle tuning in conjunction with pump wavelength tuning provides output tunability in the 530–585-nm range.

We report a femtosecond optical parametric oscillator based on a periodically poled KTiOPO_4 crystal for which quasi-phase matching is achieved with a 24-µm poling period. The singly resonant parametric oscillator, synchronously pumped by a Ti:sapphire laser at a wavelength of 758??nm, generates a signal at 1200??nm and an idler at 2060??nm. The maximum signal power conversion efficiency of the device is 22% with a pump depletion of 69%. We tune the signal wavelength over a 200-nm band by changing the cavity length. In addition, pump wavelength tuning provides output tunability in the 1000–1235-nm range.