A system and method are provided for optical homodyne detection in an optical fiber interferometer. A detection signal is obtained by interfering an optical data signal with a phase-modulated optical reference signal. The modulator for the optical reference signal is phase-locked to an oscillatory modulation waveform. In embodiments, the modulator includes a piezoelectric element. In more specific embodiments, the modulator is a piezoelectric optical fiber-stretcher.

A system and method are provided for optical homodyne detection in an optical fiber interferometer. A detection signal is obtained by interfering an optical data signal with a phase-modulated optical reference signal. The modulator for the optical reference signal is phase-locked to an oscillatory modulation waveform. In embodiments, the modulator includes a piezoelectric element. In more specific embodiments, the modulator is a piezoelectric optical fiber-stretcher.

A bending detecting system includes a light guide, a first grating and a light detector. The light guide has elongated shape and is configured to guide an incident light in a propagating direction. The light guide includes a core and a cladding disposed around the core. The first grating is disposed in a boundary area, the boundary area including an outer surface of the core, and an adjacent area that is adjacent to the outer surface. The first grating includes a first periodic structure along the propagating direction with a first pitch, and is configured to generate a first diffracted light from the incident light. The light detector is configured to detect the first diffracted light from the first grating, and detect a bending of the light guide based upon an optical feature amount of the first diffracted light.

Improvements to atom interferometers. An improved atom interferometer has a single polarization-preserving fiber, coupled for propagation of beams of two Raman frequencies, and a parallel displacement beamsplitter for separating the laser beams into respective free-space-propagating parallel beams traversing at least one ensemble of atoms. A reflector generates one or more beams counterpropagating through the ensemble of atoms. Other improvements include interposing a beam-splitting surface common to a plurality of parallel pairs of beams counterpropagating through the ensemble of atoms, generating interference fringes between reflections of the beams to generate a detector signal; and processing the detector signal to derive at least one of relative phase and relative alignment between respective pairs of the counterpropagating beams.

An atomic interferometer and methods for measuring phase shifts in interference fringes using the same. The atomic interferometer has a laser beam traversing an ensemble of atoms along a first path and an optical components train with at least one alignment-insensitive beam routing element configured to reflect the laser beam along a second path that is anti-parallel with respect to the first laser beam path. Any excursion from parallelism of the second beam path with respect to the first is rigorously independent of variation of the first laser beam path in yaw parallel to an underlying plane.

The present invention provides an interference measuring device with an optical system that can receive light reflected from a measurement object of a surface profile that is not perpendicular to an optical axis. An interference measuring device includes a light source for emitting light and an interferometric objective lens. The interferometric objective lens includes a reference mirror disposed in a reference beam path and a beam splitter that splits the incident light into a beam traveling along the reference beam path and a beam traveling along a measurement beam path. The beam splitter also combines the beam reflected off the reference mirror with the beam reflected off a measurement object disposed in the measurement beam path before emitting the combined beams. The interference measuring device further includes an imaging unit for taking an image of the combined beams forming on the unit and an aperture stop disposed in an optical path linking the interferometric objective lens, the light source, and the imaging unit together. The aperture stop is movable along an optical axis of the interferometric objective lens.

An interference observation apparatus includes a light source, a splitting beam splitter, a combining beam splitter, a beam splitter, a mirror, a beam splitter, a mirror, a piezo element, a stage, an imaging unit, an image acquisition unit, and a control unit. An interference optical system from the splitting beam splitter to the combining beam splitter forms a Mach-Zehnder interferometer. The mirror freely moves in a direction perpendicular to a reflecting surface of the mirror. The total number of times of respective reflections of first split light and second split light in the interference optical system is an even number.

Various optical systems equipped with diode laser light sources are discussed in the present application. One example system includes a diode laser light source for providing a beam of radiation. The diode laser has a spectral output bandwidth when driven under equilibrium conditions. The system further includes a driver circuit to apply a pulse of drive current to the diode laser. The pulse causes a variation in the output wavelength of the diode laser during the pulse such that the spectral output bandwidth is at least two times larger than the spectral output bandwidth under the equilibrium conditions.

A optical measurement apparatus includes: an optical system which generates a pupil image of a measurement target, using light; a polarization generator which generates a polarized light from the light; a self-interference generator which generates a plurality of beams divided from the pupil image, using the polarized light, and causes the plurality of beams to interfere with each other to generate a self-interference image; and an image analysis unit configured to extract phase data from the self-interference image, and to move the measurement target to a focus position on the basis of the phase data.

A system (1) for generating a signal from a surface (22) having a speed V in a direction U, comprising: a light source (2) emitting a Gaussian light beam along a first optical path (11); a sensor (3) able to evaluate the effects of the electromagnetic interference of the first beam; a means (2′, 4) for generating a second Gaussian light beam along a second optical path (12); a second sensor (3′) able to evaluate the effects of electromagnetic interference of the second beam; a focusing lens (5, 6) located on the first and/or the second optical path (11, 12), focusing the light beam at a distance f and defining an upstream optical path (11′, 12′); and a means (4′, 7) for routing the second beam able to redirect the second path (12′) in the direction of the first path (11′).