Embodiments relate to characterizing underwater turbulence. Initially, multispectral laser light (MLL) is generated and then converted to output laser light (OLL). The OLL is received at a polarization rotator that causes the OLL to be emitted in one of multiple modes of polarization. Next, the OLL is directed toward a target medium, where the OLL causes backscattered light to be emitted from the target medium. While using the polarization rotator to switch between the multiple modes of polarization, Stokes parameters of the backscattered light are detected and then used to characterize the underwater turbulence of the target medium.

Embodiments relate to characterizing underwater turbulence. Initially, multispectral laser light (MLL) is generated and then converted to output laser light (OLL). The OLL is received at a polarization rotator that causes the OLL to be emitted in one of multiple modes of polarization. Next, the OLL is directed toward a target medium, where the OLL causes backscattered light to be emitted from the target medium. While using the polarization rotator to switch between the multiple modes of polarization, Stokes parameters of the backscattered light are detected and then used to characterize the underwater turbulence of the target medium.

A light detection and ranging system includes a first optical source and a second optical source configured to emit respectively a first optical beam and a second optical beam that have opposite polarizations. The system also includes a first tap and a second tap configured to split respectively the first optical beam and the second optical beam into a first high-power path optical beam and a first low-power path optical beam, and a second high-power path optical beam and a second low-power path optical beam. The system also includes a first polarization beam splitter configured to combine the first high-power path optical beam and the second high-power path optical beam into a single spatial mode optical beam.

A light detection and ranging system includes a first optical source and a second optical source configured to emit respectively a first optical beam and a second optical beam that have opposite polarizations. The system also includes a first tap and a second tap configured to split respectively the first optical beam and the second optical beam into a first high-power path optical beam and a first low-power path optical beam, and a second high-power path optical beam and a second low-power path optical beam. The system also includes a first polarization beam splitter configured to combine the first high-power path optical beam and the second high-power path optical beam into a single spatial mode optical beam.

A method of performing surface profilometry includes receiving one or more polarization raw frames of a printed layer of a physical object undergoing additive manufacturing, the one or more polarization raw frames being captured at different polarizations by one or more polarization cameras, extracting one or more polarization feature maps in one or more polarization representation spaces from the one or more polarization raw frames, obtaining a coarse layer depth map of the printed layer, generating one or more surface-normal images based on the coarse layer depth map and the one or more polarization feature maps, and generating a 3D reconstruction of the printed layer based on the one or more surface-normal images.

A light detection and ranging (LIDAR) pixel includes a polarization controller, a grating coupler, and an optical mixer. The polarization controller includes a phase shifter that sets a phase of light in a first arm of the polarization controller and a second arm of the polarization controller.

A lidar system includes a laser emitting light source-044, a scanning unit, a transmitting-receiving-coaxial optical unit and a differential reception unit. The laser emitting light source includes a laser and a modulator. The transmitting-receiving-coaxial optical unit is configured to receiving receive a frequency-modulated emission light signal, and pass the same to the scanning unit and the differential reception unit, and is also configured to pass a reflected light signal to the differential reception unit. The scanning unit is configured to reflecting the frequency-modulated emission light signal to a target object at a deflectable angle, and reflect the reflected light signal from the target object to the transmitting-receiving-coaxial optical unit. The differential reception unit is configured to differentially receive the reflected light signal based on the received frequency-modulated emission light signal. With a differential reception, the laser radar system reduces noise, increases the signal-to-noise ratio, and increases the detection distance.

An optical sensing system for sensing a target object is provided. The optical sensing system includes a light source, an optical wave plate, a polarizing beam-splitting element, a reflecting element, and a sensing element. The light source provides a first linearly polarized light beam. The optical wave plate is adapted to convert the first linearly polarized light beam into a circularly polarized light beam and convert the circularly polarized light beam into a second linearly polarized light beam. The polarizing beam-splitting element is adapted to allow the first linearly polarized light beam to pass and reflect the second linearly polarized light beam. The reflecting element is adapted to reflect the circularly polarized light beam to the target object and to reflect the circularly polarized light beam from the target object. The sensing element is disposed on a transmission path of the second linearly polarized light beam.

Apparatus and associated methods relate to determining metrics of water particles in clouds by directing light pulses at a cloud and measuring a peak, a post-peak value and a high-frequency fluctuation of light signals reflected from the cloud. The light pulses include: a first pulse having circularly polarized light of a first wavelength; and a second pulse of a second wavelength. The reflected light signals include: a first reflected light signal having left-hand circular polarization of the first wavelength; a second reflected light signal having right-hand circular polarization of the first wavelength; and a third reflected light signal of the second wavelength. An extinction coefficient and a backscatter coefficient are determined based on the measured peak and post-peak slopes of the first and second reflected light signals. The measured high-frequency fluctuations of the three reflected light signals can be used to calculate cloud particle sizes.

A sensor diagnostic system includes a first sensor configured to receive a reflected signal that corresponds to a portion of a transmitted signal transmitted from a second sensor and reflected from a surface, a wavelength determination module configured to determine a first wavelength of the reflected signal that is indicative of a second wavelength of the transmitted signal, a wavelength shift detection module configured to determine a shift in at least one of the first wavelength and the second wavelength, and a sensor health analysis module configured to perform diagnostics on the second sensor based on the determined shift.