Agilent Technologies, Inc.

Hewlett-packard Company

Other

Agilent Inc.

Leonard S Cutler

Miao Zhu

Robin P Giffard

James L Johnson

John Edwin Berberian

John C Eidson

William R Trutna, Jr

William David Holland

Richard Keith Karlquist

Geraint Owen

Stanley P Woods

Joseph Alexander Dara-Abrams

Eric Stephen Johnstone

Alan B Ray

James B Prince

Richard A Baugh

Theodore Parisek

James R Collin

Lawrence J Wuerz

An apparatus and method for measuring displacement includes a light beam directed to an interferometer core that splits the light beam into first and second component beams. The first component beam is directed to a diffraction grating at approximately a Littrow angle. A diffraction is received by the interferometer core and is combined with the second component beam. The combination of the first and second component beams is measured to determine displacement of the diffraction grating.

Littrow interferometer

An apparatus and method for measuring CPT is disclosed. The apparatus includes a quantum absorber that is irradiated by radiation from an electromagnetic radiation source. The quantum absorber includes a material that exhibits CPT. The electromagnetic radiation source generates electromagnetic radiation having first and second CPT-generating frequency components. The first CPT-generating frequency component has a frequency &#x3bd;L&#x2212;&#x3bd;, and a first CPT component amplitude. The second CPT generating frequency component has a frequency &#x3bd;+&#x3bd; and a second CPT component amplitude. The apparatus also includes a detector for generating a detector signal related to the power of electromagnetic radiation that leaves the quantum absorber. The detector signal exhibits an asymmetry as a function of frequency &#x3bd; in a frequency range about a frequency &#x3bd;. The apparatus includes an asymmetry servo loop that alters one of &#x3bd;, the first CPT component amplitude, and the second CPT component amplitude to reduce the asymmetry.

Method and apparatus for reducing errors due to line asymmetry in devices utilizing coherent population trapping

An apparatus for generating a stabilized frequency signal is disclosed. The apparatus includes a quantum absorber having first, second, and third energy states. The quantum absorber is irradiated by a first radiation source that generates electromagnetic radiation having a frequency, &#x3bd;, that induces transitions between the first and third energy states. The quantum absorber is also irradiated by a second radiation source that generates electromagnetic radiation having a frequency, &#x3bd;, that induces transitions between the first and second energy states. A detector that generates a detector signal indicative of the level of radiation leaving the quantum absorber in a frequency range including &#x3bd;is used by a number of servo loops. One of the servo loops determines the value of &#x3bd;that minimizes or maximizes the detector signal and a second servo loop determines an offset signal that reduces the dependence of &#x3bd;on the intensity of the first radiation source.

Optically pumped frequency standard with reduces AC stark shift

A quantum absorber is provided having transitions that include a first transition between a first lower quantum state and an upper quantum state, and a second transition between a second lower quantum state and the upper quantum state. The first transition and the second transition have energies that correspond to frequencies of &ohgr; and &ohgr; , respectively. The lower quantum states differ in energy by an energy difference subject to a total a.c. Stark shift. Incident electro-magnetic radiation is generated. The incident electro-magnetic radiation includes main frequency components and additional frequency components. The main frequency components are at frequencies of &OHgr; and &OHgr; , equal to &ohgr; and &ohgr; , respectively, and differ in frequency by a frequency difference. The additional frequency components collectively have a spectrum. The quantum absorber is irradiated with the incident electro-magnetic radiation. Electro-magnetic radiation from the quantum absorber is detected to generate a detection signal. The frequency difference is controlled to obtain an extremum in the detection signal. The extremum indicates that the frequency difference corresponds to the energy difference between the lower quantum states. The spectrum of the additional frequency components is set to reduce the magnitude of the total a.c. Stark shift, and a frequency standard signal related in frequency to the frequency difference is provided.

Coherent population trapping-based method for generating a frequency standard having a reduced magnitude of total a.c. stark shift

A detection signal that quantifies a resonant interaction between a quantum absorber and incident electro-magnetic radiation is generated. The quantum absorber is irradiated with the incident electro-magnetic radiation. The quantum absorber absorbs a portion of the incident electro-magnetic radiation and generates fluorescent electro-magnetic radiation in response to it. The quantum absorber additionally transmits the unabsorbed portion of the incident electro-magnetic radiation. The unabsorbed portion of the incident electro-magnetic radiation is detected to generate a first signal that has a first signal-to-noise ratio. The fluorescent electro-magnetic radiation is detected to generate a second signal that has a second signal-to-noise ratio. The first signal and the second signal are combined to generate the detection signal. The detection signal has a signal-to-noise ratio greater than the first signal-to-noise ratio and the second signal-to-noise ratio.

Detection method and detector for generating a detection signal that quantifies a resonant interaction between a quantum absorber and incident electro-magnetic radiation

The frequency standard comprises a quantum absorber, a source of incident electro-magnetic radiation, a detector, a frequency difference controller, a spectrum controller and a frequency standard output. The quantum absorber has transitions including a first transition between a first lower quantum state and an upper quantum state, and a second transition between a second lower quantum state and the upper quantum state. The first transition and the second transition have energies that correspond to frequencies of &ohgr;,and &ohgr;,, respectively. The lower quantum states differ in energy by an energy difference subject to a total a.c. Stark shift. The source of incident electro-magnetic radiation is arranged to irradiate the quantum absorber. The incident electro-magnetic radiation includes main frequency components at frequencies of &OHgr;,and &OHgr;,, equal to &ohgr;,and &ohgr;,, respectively, and additionally includes additional frequency components collectively having a spectrum. The detector is arranged to receive electro-magnetic radiation from the quantum absorber and generates a detection signal in response to the received electro-magnetic radiation. The frequency difference controller controls the source to generate the main frequency components with a difference in frequency that obtains an extremum in the detection signal. The extremum indicates that the difference in frequency corresponds to the energy difference. The spectrum controller sets the spectrum of the additional frequency components to reduce the magnitude of the total a.c. Stark shift. The frequency standard output a frequency standard signal related in frequency to the difference in frequency.

Coherent population trapping-based frequency standard having a reduced magnitude of total a.c. stark shift

An oven assembly for a crystal resonator and oscillator utilizes a thermally symmetrical design to provide a high thermal gain. The oven assembly includes an encasement that forms a hermetically sealed oven chamber that is substantially cylindrical. Concentric with the oven chamber is an annular oven mass that functions as a heat reservoir for the crystal resonator that is contained within the oven mass. The cylindrical oven chamber and the concentric annular oven mass provide two levels of circular symmetry that help achieve a thermally isotropic oscillator environment. Wide-area uniform heat transfer promotes high thermal gain and minimizes thermal gradients. Another factor is the geometry and circuitry for temperature monitoring. Temperature sensors are equidistantly spaced from each other and are equidistant from the center of the oven chamber. Signals from the various thermistors are averaged to provide a more accurate temperature determination for regulating the heaters.

High thermal gain oven with reduced probability of temperature gradient

The local clocks within each node of a loosely distributed network system may be synchronized and syntonized by any of the nodes in the network. Each of the nodes contains a time packet detector (TPD) that detects and recognizes timing data packets and produces a recognition signal. This signal may be used to cause an action in the detecting node, in particular the node may contain a time service block (TSB) containing a local clock that may be used to record the time of the recognition signal. The recorded times may be used as the basis for correcting the local clocks of the nodes in the system. Transfer devices such as gateways, bridges, and routers may include TSBs and TPDs to allow for correction for the transit time of time packets through the transfer device. The TPD is normally connected within the media access device at the point of final encoding for transmission or recovery of the clock and data for receiving where the time jitter will be at a minimum.

Method for recognizing events and synchronizing clocks

A remote receiver for laser interferometer systems is split into two parts connected by a fiber optic link. The front-end of the receiver, located near the remote interferometer optics, houses only the optical components for focusing and mixing the laser beam, and transmits the beam through an optical fiber cable. The back-end of the receiver, located remotely, houses the electronic components for detecting and measuring the frequency difference to produce the signal for the measurement electronics.

Fiber-optic based remote receiver for laser interferometer systems

A method and apparatus are disclosed for optically pumping the atoms of an atomic beam into a single trap state. An atomic beam is produced and is passed through a region of weak magnetic field to produce a magnetic splitting of energy levels. The beam is illuminated with a laser beam to produce selected excitations. The spectral distribution of the laser light is selected (1) to excite the atoms of the atomic beam to excited levels from which the atoms can decay into the trap state and (2) to avoid exciting atoms out of the trap state. Particular applications of the method and apparatus are described for atomic or ionic clocks and masers.

Atomic beam device using optical pumping

A differential detection device is provided for detecting the presence of magnetic bubbles in a data stream circulating on a magnetic wafer. The device utilizes an array of columns of permalloy elements to enlarge the magnetic bubbles being detected. A change in resistance of each of a pair of adjacent permalloy columns as a bubble traverses the detector is sensed and differentially detected to signify the presence of the bubble. In one embodiment of the invention, a second detector is used in conjunction with the first detector to provide operation in a mode in which bubbles in alternate positions in the data stream are directed into alternate channels including the first and second detectors respectively. After detection, the bubbles are redirected into a single data stream, while the output signals from the two detectors are merged to produce a data output signal reproducing the original data stream.

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Los Altos Hills, CA, United States of America

Leonard S Cutler