Abstract: This invention provides a tunable laser in which a plurality of gain elements (e.g., semiconductor diodes) with a plurality of gain spectra are optically coupled to a splitting-combining means (e.g., a wavelength router or fiber-optic coupler) in parallel, and the splitting-combining means is in optical communication with a wavelength-selecting means (e.g., a diffraction grating optically coupled to a movable mirror). The tunable laser of the present invention further comprising an optical fiber, optically coupling the splitting-combining means to the wavelength-selecting means. The use of a plurality of distinct gain spectra greatly enhances the tuning range of the tunable laser in the present invention.

Abstract: A method for automatically limiting access of a client computer to data objects accessed through a server computer dynamically prevents robots or webcrawlers from obtaining too much of the server database and from dramatically reducing server performance. The method includes the steps of receiving a request for a data object, recording a log entry for the request, calculating client request values, and refusing the request if a client request value exceeds one of a set of corresponding predefined maximum request values. Each log entry contains a client identifier, timestamp, and at least one data object identifier for the request. The client request values preferably include a request frequency, which is compared with a predefined maximum request frequency, and a cumulative data request, which is compared with a data access threshold. If the client is refused access, the client identifier is added to a deny list, and future requests from the client are automatically denied.

Abstract: A laser suitable for intra-cavity laser absorption spectroscopy and for telecommunication system comprises a Bragg mirror, a multiple quantum well active region and an anti-reflective coating together with a second mirror spaced from the coating to define an external cavity, the free spectral range of the sub-cavity defined by the coating and the active region being less than two times the bandwidth of the coating and the bandwidth of the Bragg mirror being at least as great as the free spectral range of the sub-cavity.

Abstract: The present invention provides a radiation device that includes a device for retaining therein the body part in a uniform position. In addition, at least two reference materials that have attenuation characteristics are used and retained in the retaining device. The reference materials are being positioned for the comparative determination during a simultaneous irradiation of the body part and the reference materials. The attenuation characteristics of the reference materials are selected in correspondence to the attenuation characteristics of the body materials in the body part. A radiation device for simultaneously irradiating the body part and the reference materials is used to create attenuated beams. A detector is used to detect the attenuated beams as attenuated values. A calculating device is included for calculating the proportion of the body materials that define a particular body part of interest based on the attenuated values of the materials and the body part.

Abstract: A high efficiency optical interconnect (OI) deposited directly on a silicon based IC by a low temperature process that utilizes a heterogeneous crystalline structure of a III-V compound material to convert light pulses into electrical signals. The high efficiency is established by pulsing the light beams with a shorter duration than the life time of the generated carriers and by reducing the structural volume and consequently the internal capacitance of the III-V compound to a functional height of approximately 1 micron. The analog MSM characteristic of the OI is bypassed by differential two-beam signal processing, wherein the intensity difference of two synchronous light beams is transformed in two parallel OI's into two electrical signals that compensate in a central node. The resulting polarity in the node switches either a PMOS or a NMOS transistor, which connect either a positive or negative voltage to the output node.

Abstract: An intracavity frequency converted, Q-switched laser and method for operating such laser to obtain high output power in secondary pulses at a converted frequency. The secondary pulses are generated by a intracavity frequency conversion element from primary pulses at the fundamental wavelength. In accordance with the invention, after the primary and secondary pulses are generated the Q-switch is turned back on before the gain is fully depleted in the generation of the primary pulse. In particular, the Q-switch is turned back on such that a certain amount of energy of the primary pulse is retained in the laser, but late enough so that a majority of the secondary pulse is out-coupled from the laser. The Q-switched laser is well-suited for use at pulse repetition rates larger than 1/&tgr;, where &tgr; is an upper state lifetime (fluorescence lifetime) of the laser. Specifically, the laser can be operated at repetition rates of 10 kHz and higher, e.g.

Abstract: A system for automatically generating user interest profiles and delivering information to users learns a user's interests by monitoring the user's outbound communication streams, i.e., the information that the user produces either by typing (e.g., while a user is composing an e-mail message or editing a word processor document) or by speaking (e.g., while a user is engaged in a phone conversation or listening to a lecture). The system uses the monitored text to build (and possibly update) a user interest profile. The profile is constructed from current text generated by the user, so that the retrieved information reflects present user interests. In addition, the profile may also retain past user interests, so that the profile reflects a combination of past and present user interests. The system then automatically queries diverse databases for information relevant to the interest profile.

Abstract: An optical resonator has a piezoelectric element attached to a quasi-monolithic structure. The quasi-monolithic structure defines an optical path. Mirrors attached to the structure deflect light along the optical path. The piezoelectric element controllably strains the quasi-monolithic structure to change a length of the optical path by about 1 micron. A first feedback loop coupled to the piezoelectric element provides fine control over the cavity length. The resonator may include a thermally actuated spacer attached to the cavity and a mirror attached to the spacer. The thermally actuated spacer adjusts the cavity length by up to about 20 microns. A second feedback loop coupled to the sensor and heater provides a “coarse” control over the cavity length. An alternative embodiment provides a quasi-monolithic optical parametric oscillator (OPO). This embodiment includes a non-linear optical element within the resonator cavity along the optical path.

Abstract: A dual speed hard drive system with an actuator retract system capable of retracting the actuator at approximately the same speed and power in both speed modes. In one embodiment, the control of resistance is used to control the amount of back-emf current supplied to the voice coil motor. In another embodiment, the circuit selectively restrict which spindle motor winding is allowed to supply back-emf current to the voice coil motor. In yet another embodiment, a voltage or a current regulator is used to control the current flowing into the voice coil motor. In all three embodiments, the amount of back-emf current supplied to the voice coil motor is proportional to the power and speed at which the actuator is being retracted.

Abstract: An ellipsoidal solid immersion lens (ESIL) for use as a collimator for a waveguide. The ESIL has a refractive index n, an ellipsoidal surface portion defining a geometrical ellipsoid with geometrical foci F1, F2 along a major axis of length M. The ESIL has an attachment surface portion for joining to the waveguide. The attachment surface portion passes near or through the second geometrical focus F2. The geometrical foci F1, F2 are separated by a distance S=M/n, such that a substantially collimated light beam exhibiting a Gaussian type intensity profile propagating along the major axis M and entering the ESIL through the ellipsoidal surface portion converges to a Gaussian beam waist substantially at the second geometrical focus F2.

Abstract: A functional block for a CMOS circuit within the core of an integrated circuit chip and a method of making the same is disclosed. The functional block uses both thick and thin gate oxide transistors which reduces the leakage current and increases the voltage swing while permitting the device scaling in circuits made in CMOS technology. Within the functional block, the distance between a thick oxide transistor and a thin oxide transistor is chosen based on a transistor stability criterion. The thick and thin oxide transistors can be connected to identical or different voltage sources. Further, a transistor within a functional block can be chosen to be thick or thin oxide transistor based on a leakage current threshold or a voltage swing threshold.

Abstract: A deinterleaver includes three polarization interferometers and a dispersion compensator, the input light beam containing all channels passing through the dispersion compensator and the first polarization interferometer, the light beam being separated by a polarization beam splitter into an even channel beam and an odd channel beam with the even channel beam passing through a second polarization interferometer and the odd channel beam passing through a third polarization interferometer. A dispersion compensated deinterleaver as above in which all three polarization interferometers have pass bands corresponding to all channels and in which there are two output ports. A dispersion compensated deinterleaver in which the first polarization interferometer has pass bands for all channels, the second polarization interferometer has pass bands for even channels, the third polarization interferometer has pass bands for odd channels and in which there are four output ports.

Abstract: The magnetic surfaces of the magnetoresistive or magnetic tunnel junction and inductive write head and magnetic recording disk of a hard disk drive are protected from corrosion by inserting a vapor phase corrosion inhibitor (VPCI) package into the disk drive for providing additives in the vapor phase of the disk drive enclosure to maintain an equilibrium and renewable adsorbed film of metal passivators on the head and disk surfaces. The VPCI package includes at least one vapor phase corrosion inhibitor (VPCI) embedded in a polymeric matrix.

Abstract: A system and method for document retrieval is disclosed. The invention addresses a major problem in text-based document retrieval: rapidly finding a small subset of documents in a large document collection (e.g. Web pages on the Internet) that are relevant to a limited set of query terms supplied by the user. The invention is based on utilizing information contained in the document collection about the statistics of word relationships (“context”) to facilitate the specification of search queries and document comparison. The method consists of first compiling word relationships into a context database that captures the statistics of word proximity and occurrence throughout the document collection. At retrieval time, a search matrix is computed from a set of user-supplied keywords and the context database. For each document in the collection, a similar matrix is computed using the contents of the document and the context database.

Abstract: In a T-head design, it is desirable to reduce the side-writing that occurs during the write operation. The side-writing causes the track width to increase and therefore reduces the track density that can be achieved. The side-writing is caused by certain corners of the T-head producing extraneous fluxes over the magnetic disk. The extraneous fluxes write to the magnetic disk, causing the track width to be increased. The present invention recesses part of the T-head from the air bearing surface by a focused ion beam milling, an ion milling, or an etching process. The extraneous fluxes are therefore recessed from the magnetic disk by a shallow distance sufficient to prevent writing to the magnetic disk, but not so great a distance to inhibit the flux carrying capacity of the structure to the actively writing pole tip.

Abstract: A flux guided magnetic tunnel junction head includes a ferromagnetic pinned layer having an active region with a front edge recessed from a sensing surface, and a non-active region located between the sensing surface and the active region. The non-active region of the ferromagnetic pinned layer is rendered substantially non-conducting by chemically processing the ferromagnetic material of the ferromagnetic pinned layer in this region. The flux guided MTJ head also includes a ferromagnetic free layer having a front edge substantially coplanar with a sensing surface. The ferromagnetic free layer can function as a flux guide to direct magnetic flux from a recording medium to the tunnel junction. The location of the front edge of the ferromagnetic pinned layer prevents any shorting of the flux guided MTJ head occurring when the head is lapped at the sensing surface.

Abstract: A monolithically integrated, mode-locked vertical cavity surface emitting laser (VCSEL) for emitting ultrafast high power pulses. The resonator of the VCSEL has an active medium for emitting a radiation, a spacer for extending the resonator to a length L at which a significant number N of axial modes of the radiation are supported in the resonator and a saturable absorber for mode-locking. The VCSEL has an arrangement for stabilizing the resonator such that one transverse mode of the radiation is supported within the resonator. The VCSEL also has an arrangement for compensating dispersion of the radiation occurring in the resonator.

Abstract: An optical channel monitor (OCM) or filter for analyzing an incident light carrying a number of narrow band signal channels such as WDM or DWDM channels. The OCM or filter use an acousto-optic tunable filter to receive and refract from an incident light a refracted light such that the refracted light contains a test channel with a center frequency &ngr;0. A first birefringent element is provided for filtering from the refracted light a first polarized light and a second polarized light orthogonal to the first polarized light. The transmission curves are engineered such that the transmissions of the first and second polarized light are substantially equal at the center frequency &ngr;0 of the test channel. The OCM or filter has a second birefringent element for filtering from the first polarized light a first polarized portion and a second polarized portion.

Abstract: A method of fabricating multiple superimposed Bragg gratings in the core of a portion of a photosensitive fiber is provided where only one common phase-mask is used. The multiple superimposed Bragg gratings are inscribed in the portion of the photosensitive fiber by applying different predetermined longitudinal stresses to the portion for each corresponding writing. The different predetermined longitudinal stresses are applied to the portion of the photosensitive fiber by stretching the portion along its longitudinal axis bi-directionally and simultaneously such that the centers of all fiber Bragg gratings imprinted in the portion are substantially superimposed at the center of the portion of the photosensitive fiber.

Abstract: A spectrometer for determining a spectrum of a light by using a mirror to reflect the light so that the light forms an intensity standing wave pattern through superposition of an incident portion of the light and a reflected portion of the light. The spectrometer is equipped with an intensity detector whose thickness is less than a shortest wavelength of the light being examined and which is semitransparent over the spectrum. The spectrometer has a mechanism to provide relative movement between the mirror and the intensity detector such that the intensity detector registers a variation of the intensity standing wave pattern. An analyzer, such as a Fourier transform analyzer, is employed to determine the spectrum of the light from that variation of the intensity standing wave pattern.