A device and method for phase imaging and element detection based on wavefront modulation are provided to overcome the disadvantages of an existing interferometry such as twin image elimination, limit resolution, under-sampling wavefront measurement, and multi-modal measurement. From the perspective of light field encoding, the accurate measurement to a complex amplitude of a light field to be measured is completely achieved by the iterative calculation, and at the same time, a twin image problem may be effectively eliminated, and it has the multi-modal (multi-wavelength) reconstruction ability. Theoretically, it is able to reach the diffraction limit resolution, may be widely used in phase imaging, optical element surface-type detection, polarization distribution measurement and the like, and it has a wide range of applications.

An entanglement-enhanced interferometry system includes a source of correlated photons configured to two-mode squeezed vacuum (TMSV), a polarizing splitter or off-axis polarizing coupler configured to separate the correlated photons into two paths, a polarization control device configured to rotate polarization of photons on one of the two paths relative to the photons on the other of the two paths in order to make photons indistinguishable, a coupler configured to entangle the indistinguishable photons, and a polarization maintaining fiber-based interferometer configured to use the entangled photons as the input state. The source of correlated photons might be a nonlinear element such as a periodically poled element such as a lithium niobate bulk crystal or waveguide. The interferometer might be a Mach-Zehnder or a common path configuration. The coupler might be a 50:50 coupler or a polarizing coupler 45 degrees off-axis.

An interferometer for use in remote sensing systems includes a beam splitter that separates an input wave into a reflected wave, which travels along a first optical path within an upper interferometer arm, and a transmitted wave, which travels along a second optical path within a lower interferometer arm. The reflected and transmitted waves are subsequently recombined by the beam splitter for imaging onto a sensor. A highly dispersive element is incorporated into at least one of the pair of interferometer arms. Due to anomalous dispersion, a frequency shift in a wave transmitted through a dispersive element changes the optical path length within its corresponding arm. As a result, the recombined wave produces an interference pattern with a measurable phase change that can be utilized to calculate the original frequency shift in the input wave with great precision and potential sub-Hertz sensitivity.

A simultaneous phase-shift point diffraction interferometer and method for detecting wave aberration. The interferometer comprises an ideal spherical wave generation module, an optical system to be measured, an image plane mask, a polarization phase shift module, a two-dimensional polarization imaging photodetector and a data processing unit. Single photodetector is adopted to realize simultaneous detection of more than three phase shift interference patterns, and has the advantages that environmental interference suppression, a flexible optical path, high measurement accuracy, and calibration of system errors of the interferometer may be realized.

Apparatus and associated methods relate to determining the wavelength of a narrow-band light beam. The narrow-band light beam is passed through an optical filter. The optical filter has complementary and monotonically-varying transmission and reflection coefficients within a predetermined band of wavelengths. The predetermined band of wavelengths includes the wavelength of the narrow-band light beam. A first photodetector detects amplitude of a first portion of the narrow-band light beam transmitted by the optical filter. A second photodetector detects amplitude of a second portion of the narrow-band light beam reflected by the optical filter. The wavelength of the narrow-band light beam is determined, based on a ratio of the determined amplitudes of the first and second portions of the narrow-band light beam transmitted and reflected, respectively.

The present disclosure provides a phase sensitivity calibration method based on a phase generated carrier (PGC) technology, which is characterized in that in the operation process of a PGC algorithm, an additional calibration signal with a phase of known magnitude is applied through a phase modulator. This signal is demodulated through an arctangent algorithm or a differential cross multiplication algorithm, and a demodulated output value corresponding to a unit phase in the algorithm is obtained. The phase of known magnitude can be obtained by converting a carrier modulation depth parameter according to a certain ratio.

The present disclosure relates to an integrated phase detector. In an embodiment, a first multi-mode interference coupler that receives the optical signal and outputs optical signals with a plurality of modes, and a second multi-mode interference coupler that receives one of the optical signals with the plurality of modes and a modulated signal generated through performing a phase modulation on another of the optical signals with the plurality of modes by the microwave signal, and outputs a first optical interference signal and a second optical interference signal may be included.

The present disclosure provides a phase sensitivity calibration method based on a phase generated carrier (PGC) technology, which is characterized in that in the operation process of a PGC algorithm, an additional calibration signal with a phase of known magnitude is applied through a phase modulator. This signal is demodulated through an arctangent algorithm or a differential cross multiplication algorithm, and a demodulated output value corresponding to a unit phase in the algorithm is obtained. The phase of known magnitude can be obtained by converting a carrier modulation depth parameter according to a certain ratio.

Method and apparatus for determining the wavelength of a light beam are provided. An input light beam is received, and light from the input light beam is distributed to multiple channels. At a first pair of interferometer cavities that has a first free spectral range, two of the multiple channels of light are received. The intensity of light reflected from the first pair of cavities is measured, and a first estimate of the wavelength or optical frequency of the input light beam is determined based on measurements of interference signals from the first pair of cavities and an initial estimate of the wavelength or optical frequency. At a second pair of cavities that has a second free spectral range smaller than the first free spectral range, another two of the multiple channels of light are received. The intensity of light from the second pair of cavities is measured, and a second estimate of the wavelength or optical frequency of the input light beam is determined based on the first estimate and measurements of interference signals from the second pair of cavities, in which the second estimate is more accurate than the first estimate.

A system comprises an electromagnetic radiation source, a polarizing element, a mode converter, an optical fiber, and a measurement device. The polarizing element receives electromagnetic radiation produced by the electromagnetic radiation source and outputs linearly-polarized electromagnetic radiation having a linear polarization angle .sub.1. The mode converter converts the linearly-polarized electromagnetic radiation to an orbital angular momentum (OAM) mode of linearly-polarized electromagnetic radiation with topological charge L.sub.i. The OAM mode of linearly-polarized electromagnetic radiation is a superposition of first and second OAM modes with topological charges L.sub.i and opposite circular polarizations. The optical fiber supports propagation of the first and second OAM modes with an absolute effective index difference n.sub.eff greater than or equal to 510.sup.3, such that linearly-polarized electromagnetic radiation with linear polarization angle .sub.2 is emitted by the optical fiber. The measurement device is configured to determine a property of the electromagnetic radiation based on the polarization angle .sub.2.