摘要:
A device for optically detecting and distinguishing airborne liquid water droplets and ice crystals includes an illumination portion and a detection portion. The illumination portion outputs a circularly polarized illuminating beam. The detection portion receives circularly polarized backscattered light from moisture in the cloud, in response to the illuminating beam. The circularly polarized backscattered light is passed through a circular polarizer to convert it into linearly polarized backscattered light, which is split into two components. Each of the two components is optionally subject to further linear polarization to filter out any leakage-type orthogonal polarization. The two components are then optically detected and the resulting detection signals are used to calculate one or more parameters reflective of the presence or absence of airborne ice crystals and/or water droplets.
摘要:
A device for optically detecting and distinguishing airborne liquid water droplets and ice crystals includes an illumination portion and a detection portion. The illumination portion outputs a circularly polarized illuminating beam. The detection portion receives circularly polarized backscattered light from moisture in the cloud, in response to the illuminating beam. The circularly polarized backscattered light is passed through a circular polarizer to convert it into linearly polarized backscattered light, which is split into two components. Each of the two components is optionally subject to further linear polarization to filter out any leakage-type orthogonal polarization. The two components are then optically detected and the resulting detection signals are used to calculate one or more parameters reflective of the presence or absence of airborne ice crystals and/or water droplets.
摘要:
An airborne multiple field-of-view water droplet sensor includes an illumination portion and a detection portion. The illumination portion includes a first optical beam emitter configured to output a light beam. The detection portion includes a kaleidoscope configured to channel a first portion of the backscattered light towards an inner reflective surface of a circle-to-line converter, a multiple field of view subsystem having at least a first detector configured to receive light reflected by the circle-to-line converter, and a single field-of-view subsystem configured to receive a second portion of the backscattered light, the second portion not having been reflected by the circle-to-line converter. The single field-of-view subsystem may include a dual channel circular polarization detector for distinguishing between liquid water droplets and ice crystals based on information in the single field-of-view.
摘要:
In one aspect, methods of determining a size distribution of water droplets in a cloud are described herein. In some embodiments, a method of determining a size distribution of water droplets in a cloud comprises sampling a depth of a cloud with a beam of electromagnetic radiation, measuring echo intensities of the electromagnetic radiation returned from the cloud with a detector, determining a measured optical extinction coefficient from the measured echo intensities, determining a measured backscatter coefficient from the measured echo intensities, determining a lidar ratio from the measured optical extinction coefficient and the measured backscatter coefficient, determining from the lidar ratio a value pair comprising a shape parameter (μ) and median volume diameter (DMVD) of the water droplets, and determining a size distribution of the water droplets using the value pair (μ, DMVD).
摘要:
In one aspect, methods of determining a size distribution of water droplets in a cloud are described herein. In some embodiments, a method of determining a size distribution of water droplets in a cloud comprises sampling a depth of the cloud with a beam of electromagnetic radiation, measuring a scattering signal of the electromagnetic radiation returned from the cloud over a range of field of view angles to provide a measured scattering curve [ptotal(θ)], removing a portion of the measured scattering curve, replacing the removed portion with an extrapolation of the remaining measured scattering curve to provide an estimated scattering curve, and determining a first estimate droplet size distribution [n(1)(D)] from the estimated scattering curve.
摘要:
An airborne multiple field-of-view water droplet sensor includes an illumination portion and a detection portion. The illumination portion includes a first optical beam emitter configured to output a light beam. The detection portion includes a kaleidoscope configured to channel a first portion of the backscattered light towards an inner reflective surface of a circle-to-line converter, a multiple field of view subsystem having at least a first detector configured to receive light reflected by the circle-to-line converter, and a single field-of-view subsystem configured to receive a second portion of the backscattered light, the second portion not having been reflected by the circle-to-line converter. The single field-of-view subsystem may include a dual channel circular polarization detector for distinguishing between liquid water droplets and ice crystals based on information in the single field-of-view.
摘要:
A waveguide (10) is provided having a two-dimensional optical wavelength Bragg grating (20) embedded within a semiconductor laser medium (16). More particularly, the waveguide (10) includes an active region (16) sandwiched between n-doped and p-doped cladding layers (14, 22). The two-dimensional Bragg grating (20) is formed in the active region (16). Upper and lower electrodes (24, 26) are defined on opposite sides of the cladding layers (14, 22) to complete the waveguide structure (10). The two-dimensional grating (20) provides simultaneous frequency selective feedback for mode control in both the longitudinal and lateral directions.
摘要:
A method of fabricating a membrane structure for a diffractive phased array assembly is provided. The method includes the steps of providing a wafer having a body and at least a membrane layer and a backside layer disposed on opposite faces of the body, forming a grating pattern on a surface of the membrane layer, and forming a window through the wafer to expose a back surface of the membrane, thereby allowing light to pass through the membrane.
摘要:
A method of fabricating a membrane structure for a diffractive phased array assembly is provided. The method includes the steps of providing a wafer having a body and at least a membrane layer and a backside layer disposed on opposite faces of the body, forming a grating pattern on a surface of the membrane layer, and forming a window through the wafer to expose a back surface of the membrane, thereby allowing light to pass through the membrane.
摘要:
As edge-emitting semiconductor laser incorporating a narrow waveguide design is disclosed. The narrow waveguide expands the lateral mode size, creates a large modal spot size, and insures higher-order modes are beyond cutoff. Separate current confinement allows the current injection region to match the mode size. The resulting device exhibits single-mode operation with a large spot-size to high output powers.