An optical coherence tomography (OCT) engine includes a digital Fourier-Transform (dFT) spectrometer, a tunable delay line, and a high-speed optical phased array (OPA) scanner integrated onto a single chip. The broadband dFT spectrometer offers superior signal-to-noise ratio (SNR) and fine axial resolution; the tunable delay line ensures large imaging depth by circumventing sensitivity roll-off; and the OPA can scan the beams at GHz rates without moving parts. Unlike conventional spectrometers, the dFT spectrometer employs an optical switch network to retrieve spectral information in an exponentially scaling fashion—its performance doubles with every new optical switch added to the network. Moreover, it also benefits from the Fellgett's advantage, which provide a significant SNR edge over conventional spectrometers. The tunable delay line balances the path length difference between the reference and sample arms, avoiding any need to sample high-frequency spectral fringes.

A laser interferometer includes a laser light source configured to emit first laser light; an optical modulator that includes a resonator element and is configured to generate second laser light including a modulation signal; a light receiving element configured to receive the second laser light and third laser light including a sample signal; and a calculation unit configured to calculate a displacement of an object to be measured from a light reception signal based on a reference signal, in which the calculation unit includes a preprocessing unit configured to execute a preprocessing of extracting a frequency modulation component from the light reception signal and output a preprocessing signal, a demodulation processing unit configured to mix the preprocessing signal with orthogonal signals to obtain a mixed signal and then execute a demodulation processing of extracting the sample signal from the mixed signal, and an orthogonal signal generation unit configured to generate the orthogonal signals based on a phase of the reference signal and an amplitude of the preprocessing signal.

A LiDAR process executed by a signal processing component of a LiDAR apparatus, including: receiving LiDAR signal data representing a signal received at an optical receiver of a LiDAR apparatus and including a scattered and/or reflected portion of an optical signal transmitted by an optical transmitter of the LiDAR apparatus and encoded with a known digital signal, the scattered and/or reflected portion of the transmitted optical signal having been scattered and/or reflected from an object spaced from the LiDAR apparatus by a distance, and having a Doppler shifted angular frequency due to radial motion of the object relative to the LiDAR apparatus; processing the LiDAR signal data to generate corresponding frequency compensated signal data representing a frequency compensated signal corresponding to the received signal, but in which the Doppler shifted angular frequency has been removed and the known digital signal is encoded into the amplitude of the frequency compensated signal; and correlating the frequency compensated signal with a template of the known digital signal to generate a corresponding measurement of the distance of the object from the LiDAR apparatus.

A frequency shift light modulator includes a resonator and a diffraction grating including a plurality of grooves arranged in parallel in a displacement direction of the resonator, and the diffraction grating is provided on the resonator. By providing the diffraction grating on the resonator, it is easy to realize miniaturization and increase in accuracy of the frequency shift light modulator. Further, it is easy to realize application to a high frequency region in a MHz band, that is, high frequency modulation. It is possible to efficiently obtain an effect based on a combination of the resonator and the diffraction grating.

A frequency shift light modulator includes a resonator and a diffraction grating including a plurality of grooves arranged in parallel in a displacement direction of the resonator, and the diffraction grating is provided on the resonator. By providing the diffraction grating on the resonator, it is easy to realize miniaturization and increase in accuracy of the frequency shift light modulator. Further, it is easy to realize application to a high frequency region in a MHz band, that is, high frequency modulation. It is possible to efficiently obtain an effect based on a combination of the resonator and the diffraction grating.

A polarization-separated, phase-shifted interferometer can generate interferograms without moving parts. It uses a phase shifter, such as an electro-optic phase modulator, to modulate the relative phase between sample and reference beams. These beams are transformed into orthogonal polarization states (e.g., horizontally and vertically polarized states) and coupled via a common path (e.g., polarization-maintaining fiber) to a polarizing beam splitter (PBS), which sends them into separate sample and reference arms. Quarter-wave plates in the sample and reference arms rotate the polarization states of the sample and reference beams so they are coupled out of the PBS to a detector via a 45° linear polarizer. The polarizer projects the aligned polarization components of the sample and reference beams onto the detector, where they interfere with known relative phase to produce an output that can be used to map surface topography of the test object.

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 method performs phase shift interferometry to detect irregularities of a surface of a wafer after the wafer has been placed into an interferometer and while the wafer is vibrating. Additionally, a system and a non-transitory computer-readable storage medium have computer-executable instructions embodied thereon for performing phase shift interferometry to detect irregularities of a surface of a wafer after the wafer has been placed into an interferometer and while the wafer is vibrating.

A laser interferometer includes: a laser light source configured to emit first laser light; an optical modulator that includes a resonator and that is configured to modulate the first laser light using the resonator and to generate second laser light including a modulation signal; a photodetector configured to receive the second laser light and third laser light including a sample signal generated by reflecting the first laser light from an object to be measured, and to output a light reception signal; an optical coupler that has a function of splitting the first laser light and a function of splitting combined light of the second laser light and the third laser light; a first collimator configured to collimate the first laser light split by the optical coupler; a second collimator configured to collimate the first laser light split by the optical coupler; a first optical wiring; a second optical wiring; a third optical wiring; and a fourth optical wiring.

A refractive index measurement method uses an interference optical system which divides light from a light source having a plurality of discrete wavelengths into test light and reference light, causes the test light transmitted through the target to interfere with the reference light, and detect the interference light. The refractive index measurement method determines a first optical delay amount of the interference optical system so that a first and a second wavelength become adjacent to a wavelength corresponding to an extremal value of a phase of the interference light, measures phases of interference light at the first and second wavelengths at the first optical delay amount, and calculates a phase difference between a plurality of the discrete wavelengths at a predetermined optical delay amount using the first optical delay amount, the phases of the interference light at the first and second wavelengths to calculate the refractive index of the target.