A method for providing a search result list. The method includes receiving a search request from a searcher (12). In a database of search listings (24) in which each search listing is associated with an advertiser (30) and includes at least one search term and a bid amount by the advertiser, search listings generating a match with the search request are identified. A predetermined number of identified search listings (38) are selected according to bid amount for display to the searcher (16). The identified search listings are arranged for display in a random order as the search result list. The search result list is then communicated to the searcher.

Improved system and method for influencing a position on a search result list generated by a computer network search engine

Squeezed states of the electromagnetic field have been generated by nondegenerate four-wave mixing due to Na atoms in an optical cavity. The optical noise in the cavity, comprised of primarily vacuum fluctuations and a small component of spontaneous emission from the pumped Na atoms, is amplified in one quadrature of the optical field and deamplified in the other quadrature. These quadrature components are measured with a balanced homodyne detector. The total noise level in the deamplified quadrature drops below the vacuum noise level.

Observation of squeezed states generated by four-wave mixing in an optical cavity

The control of the broadband frequency comb emitted from a mode-locked femtosecond laser has permitted a wide range of scientific and technological advances--ranging from the counting of optical cycles for next-generation atomic clocks to measurements of phase-sensitive high-field processes. A unique advantage of the stabilized frequency comb is that it provides, in a single laser beam, about a million optical modes with very narrow linewidths and absolute frequency positions known to better than one part in 10(15) (ref. 5). One important application of this vast array of highly coherent optical fields is precision spectroscopy, in which a large number of modes can be used to map internal atomic energy structure and dynamics. However, an efficient means of simultaneously identifying, addressing and measuring the amplitude or relative phase of individual modes has not existed. Here we use a high-resolution disperser to separate the individual modes of a stabilized frequency comb into a two-dimensional array in the image plane of the spectrometer. We illustrate the power of this technique for high-resolution spectral fingerprinting of molecular iodine vapour, acquiring in a few milliseconds absorption images covering over 6 THz of bandwidth with high frequency resolution. Our technique for direct and parallel accessing of stabilized frequency comb modes could find application in high-bandwidth spread-spectrum communications with increased security, high-resolution coherent quantum control, and arbitrary optical waveform synthesis with control at the optical radian level.

/pdf/molecular-fingerprinting-with-the-resolved-modes-of-a-54pbyogvoq.pdf

Molecular fingerprinting with the resolved modes of a femtosecond laser frequency comb

https://engineering.purdue.edu/~fsoptics/articles/Ultrafast_optical_pulse_shaping_tutorial-Weiner.pdf

Ultrafast optical pulse shaping: A tutorial review

The application of reciprocity principles in optics has a long history that goes back to Stokes, Lorentz, Helmholtz and others. Moreover, optical applications need to be seen in the context of applications of reciprocity in particle scattering, acoustics, seismology and the solution of inverse problems, generally. In some of these other fields vector wave propagation is, as it is in optics, of the essence. For this reason the simplified approach to light wave polarization developed by, and named for, Jones is explored initially to see how and to what extent it encompasses reciprocity. The characteristic matrix of a uniform dielectric layer, used in the analysis of interference filters and mirrors, is reciprocal except when the layer is magneto-optical. The way in which the reciprocal nature of a characteristic matrix can be recognized is discussed next. After this, work on the influence of more realistic attributes of a dielectric stack on reciprocity is reviewed. Some of the numerous technological applications of magneto-optic non-reciprocal media are identified and the potential of a new class of non-reciprocal components is briefly introduced. Finally, the extension of the classical reciprocity concept to systems containing components that have nonlinear optical response is briefly mentioned.

https://iopscience.iop.org/article/10.1088/0034-4885/67/5/R03/pdf

Reciprocity in optics

A new scheme that shows large angular dispersion is proposed and demonstrated. The key idea to this method is a virtually imaged phased array (VIPA). The angular dispersion of a VIPA is 10–20 times larger than those of common diffraction gratings, which have blaze angles of ~30 deg. With the VIPA, wavelength demultiplexing for 10 channels with 0.8-nm spacing is achieved. Low polarization-state dependence (~0.1 dB) is also confirmed.

Large angular dispersion by a virtually imaged phased array and its application to a wavelength demultiplexer.

A symmetric nonlinear Mach–Zehnder interferometer containing a Kerr medium performs the operation of squeezing. The operation is performed by the interference of cotraveling waves, and the pump wave is removed. This mechanism is broadband. We analyze the operation of the interferometer and determine the degree of shot-noise reduction achieved in a balanced detector. A modification of the interferometer into a fiber ring reflector is described that accomplishes the squeezing and the pump separation.

Squeezing of pulses in a nonlinear interferometer

An optical apparatus for producing chromatic dispersion. The apparatus includes a virtually imaged phased array (VIPA) generator, a mirror and a lens. The VIPA generator receives an input light at a respective wavelength and produces a corresponding collimated output light traveling from the VIPA generator in a direction determined by the wavelength of the input light, the output light thereby being spatially distinguishable from an output light produced for an input light at a different wavelength. The mirror has a cone shape, or a modified cone shape. The lens focuses the output light traveling from the VIPA generator onto the mirror so that the mirror reflects the output light. The reflected light is directed by the lens back to the VIPA generator. In this manner, the apparatus provides chromatic dispersion to the input light. The modified cone shape of the mirror can be designed so that the apparatus provides a uniform chromatic dispersion to light in the same channel of a wavelength division multiplexed light.

Optical apparatus which uses a virtually imaged phased array to produce chromatic dispersion

A new type of optical isolator for fibers is proposed in this paper. A birefringent wedge used to separate and combine the polarized light is developed, giving the isolator low forward loss and high isolation. The antireflection process at the fiber endface reduces the forward loss and reflected return. A forward loss of 0.8 dB, a backward loss of 35 dB, and a reflected return of −32 dB were obtained. These characteristics were measured from fiber to fiber using multimode fibers with 50-μm core diam at a wavelength of 1.3 μm. Details of the design, fabrication, and characteristics of this isolator are presented.

Compact optical isolator for fibers using birefringent wedges

A polarization rotation compensator and an optical isolator using the same are described. The optical isolator comprises a first birefringent wedge plate; a polarization rotation compensator composed of a combination of a half-wave plate whose principal axis is inclined at an angle of θ/2 with respect to the plane of polarization of the incident light and a quarter-wave plate whose principal axis is inclined at an angle of θ with respect to the plane of polarization of the incident light; a Faraday rotator; and a second birefringent wedge plate; wherein the Faraday rotator, quarter wavelength plate, and half-wavelength plate are respectively arranged in the order of propagation of the backward light or of the forward light.

Masataka Shirasaki

Papers

Large angular dispersion by a virtually imaged phased array and its application to a wavelength demultiplexer.

Squeezing of pulses in a nonlinear interferometer

Optical apparatus which uses a virtually imaged phased array to produce chromatic dispersion

Compact optical isolator for fibers using birefringent wedges

Polarization rotation compensator and optical isolator using the same