Leland Stanford Junior University

Varian Associates, Inc.

United States of America As Represented by the Secretary of the Air Force

Marvin Chodorow

Herbert J Shaw

Loren F Stokes

Michel J Digonnet

Robert Spencer Symons

Ross A Lemons

Rudolf Kompfner

A pair of small diameter optical fibers are arranged in a side-by-side configuration, the first fiber providing a pumping source, and the second fiber doped with a material which will lase at the signal frequency. The signal to be amplified propagates through the second fiber to stimulate emission of coherent light from the lasing material, resulting in amplification of the signal. The refractive index of the first and second fibers are selected such that the signal in the second fiber is well guided, while the pumping light in the first fiber is unguided, yielding low losses in the second fiber but high transfer of the pumping light from the first fiber to the second fiber.

Fiber optic amplifier

A fiber optic sensor comprises a length of optical fiber, forming a loop, and a fiber optic directional coupler for optically closing the loop. The loop and coupler form a resonant cavity for light circulating therethrough. A PZT cylinder, about which the fiber loop is wrapped, is utilized to control the total round trip phase delay of the circulating light, and thus, control the intensity of the optical output signal. The phase delay is adjusted to a point where the optical output signal is at maximum sensitivity to changes in phase. When the fiber loop is exposed to, e.g., acoustic waves, the loop length changes correspondingly, thereby causing the phase delay, and thus, the optical output signal to vary. By detecting variations in output signal intensity, the frequency and intensity of the acoustic waves may be determined. The sensor also includes a feedback system for stabilizing the fiber loop against low frequency thermal drift.

Stabilized fiber optic sensor

A Brillouin ring laser comprises a fiber optic resonator formed from a loop of fiber optic material and a fiber optic directional coupler for optically closing the loop.

Brillouin ring laser

An optical fiber bidirectional amplifier includes a pair of small diameter optical fibers, arranged in a side-by-side configuration, the first fiber providing a pumping source and the second fiber doped with a material which will lase at the frequency of the signal to be amplified. The signal to be amplified propagates through the second fiber to stimulate emission of coherent light from the lasing material, resulting in amplification of the signal. The refractive indexes of the first and second fibers are substantially identical, but the coupling characteristic provided by the geometrical relationship between the pair of fibers yields a wavelength dependent coupling efficiency. Specifically, the coupling efficiency at the wavelength of the pumping source is relatively high, while the coupling efficiency at the wavelength of the signal to be amplified is relatively low. Thus, the pumping illumination is coupled from the first fiber to the second fiber to stimulate the doping material in the second fiber, while the signal to be amplified remains relatively uncoupled, and is amplified by the coherent light emitted by the lasing material.

An electron-beam tube for generating high microwave power at high frequencies comprises a fast-wave circuit such as a hollow waveguide. The circuit wave has a component of electric field perpendicular to its propagation axis. This field interacts with motions of the electrons transverse to the axis, in particular cyclotron rotation in an axial magnetic field. The above features are common to the well-known 'gyrotrons'. In the inventive tube the fast-wave circuit has means for locking a linearly polarized transverse-electric mode to the orientation of a circuit member such as the ridge in a ridged waveguide. The member (ridge) rotates spirally with distance along the guide. The added periodicity permits interaction with a space harmonic of the circuit wave. The -1 harmonic has a dispersion characteristic which provides beam-wave interaction over a wider frequency range than is possible in prior-art tubes of the gyrotron type.

Electron tube with transverse cyclotron interaction

A fiber optic resonator comprises a single strand of optical fiber forming a loop and a fiber optic directional coupler for optically closing the loop. The length of the loop is selected to cooperate with the phase shift of the coupler to provide a resonant cavity, and the coupling constant is selected to provide full or maximum resonance with zero output power.

Fiber optic resonator

In a gyrotron electron tube of the gyro-klystron or gyro-monotron type, having a cavity supporting an electromagnetic mode with circular electric field, spurious resonances can occur in modes having noncircular electric field. These spurious resonances are damped and their frequencies shifted by a circular groove in the cavity parallel to the electric field.

Mode suppression means for gyrotron cavities

A fiber optic rotation sensing interferometer based on the Sagnac effect in which mechanical rotation introduces measurable shifts in the phase of optical signals transversing a closed path. The interferometer includes the closed optical path made up of a multi-turn fiber optic loop, a directional coupler or couplers, and an amplifier. A pulse of electromagnetic radiation is fed into the optical path by means of a pulsed electromagnetic source such as a laser and a beam splitter. The beam splitter splits the pulse into two pulses which undergo multiple circulations about the optical path in opposite directions. The directional couplers non-destructively sample the two pulses after each pass therethrough and send the pair of pulse samples to the beam splitter once each circulation. The beam splitter sends these pulse pair samples to a detector and signal processor once each circulation. The detector measures the instantaneous relative phase shift between the two pulse samples in each of the multiple pulse pairs and outputs phase information once each circulation. This phase information is converted by the signal processor into the angle of rotation or into rotation rate of the interferometer.

Fiber optic rotation sensing interferometer

A method of and apparatus for imaging objects utilizing acoustic waves wherein an acoustic beam or beams are generated at one or more frequencies and are focused into proximity with the object to generate output acoustic energy at a different frequency or frequencies resultant from nonlinear interactions with the resultant production, after detection and conversion to electric output signals, of high resolution, enhanced images.

Growing community of inventors

Stanford, CA, United States of America

Marvin Chodorow