Showing papers on "Extinction ratio published in 1979"

Remote Sounding of High Clouds: I. Calculation of Visible and Infrared Optical Properties from Lidar and Radiometer Measurements

Abstract: This article describes a method of determining the visible and infrared properties of high ice clouds using a ground-based lidar and infrared (IR) radiometer. A method of calibrating the lidar is described. This is followed by a method for the correction of the cloud backscatter coefficients for pulse attenuation in the clouds, using an experimentally determined backscatter to extinction ratio k. The IR emissivity is then calculated by assuming a value for the ratio between the visible extinction coefficient and the IR absorption coefficient which is invariant with altitude. This ratio is altered until the computed radiance is equal to the measured cloud radiance. Errors in the calculation of the backscatter coefficient, the visible and the IR optical depths and the IR emissivity are assessed for various errors in the backscatter to extinction ratio. It is found that errors in the cloud optical depth become extremely sensitive to errors in k when the cloud visible optical depth becomes large. How...

Efficient LiNbO3 balanced bridge modulator/switch with an ion‐etched slot

Abstract: A simple modified balanced bridge modulator or switch is reported. The modulator is comprised of only straight waveguides and an ion‐etched slot used for a conventional phase shifter. The slot excavated at the center of two coupled waveguides solves the coupling of them. 3‐dB coupler monitoring is performed here by a metal loading. The modulator is fabricated by diffusing Ti into z‐cut LiNbO3. Each patterned waveguide is fabricated by diffusing Ti into z‐cut LiNbO3. Each patterned waveguide is 7 μm wide and the spacing is 7 μm. The 3‐dB coupler is 2.9 mm long, and the excavated slot is 15 mm long, 4 μm wide, and 4.5 μm deep. The overall length is 20.8 mm. For the TM‐like fundamental mode, the half‐wave voltage was 2.8 V, the extinction ratio was −15 dB, and the optical insertion loss was as low as 2.6 dB at the 1.15‐μm wavelength.

Design and development of a high-speed electrooptic A/D converter

Abstract: A detailed analysis of a high-speed electrooptic guided wave analog-to-digital (A/D) converter has been performed. It is concluded that the development of converters in the 4-6 bit 1-2-GS/s range should be feasible. Analyses are presented which detail the design considerations for the electrooptic modulator chip, the laser sampler, and the analog signal amplifier. A design plan is presented for a 6-bit 1-GS/s converter which utilizes an array of 6 LiTaO_3 interferometric waveguide modulators to perform the conversion and a frequency-doubled mode-locked Nd:YAG laser to perform the sampling of analog signals having 500-MHz bandwidths. Preliminary waveguide device results are also reported, including the successful demonstration of an interferometric modulator with a 17-dB (98-percent) extinction ratio.

A large‐aperture electro‐optic diffraction modulator

Abstract: Efficient modulation of a large‐diameter light beam based on diffraction by an electro‐optic phase grating has been demonstrated. The modulator consists of a y‐cut lithium niobate crystal with interdigital electrodes on one surface. With a polarized HeNe laser beam incident normal to the surface, an extinction ratio of 100 : 1 was obtained for the zeroth‐order transmitted beam at an applied voltage of 1650 V for single‐pass transmission. This device has been used to modulate a retroreflected beam in an optical communications experiment, with good performance for aperture areas greater than 15 cm2 and incidence angles up to 30°.

GaAs Rib-Waveguide Directional-Coupler Switch with Schottky Barriers

Abstract: A new type of GaAs electro-optic directional-coupler switch for monolithic integrated optics has been proposed and demonstrated. The switch was fabricated from a pair of closely spaced low-loss (α2.2 dB/cm at 1.15 µm) single-mode rib-waveguides with Au Schottky barriers. A 30 dB extinction ratio in the input channel was measured at a reverse-bias voltage of24 V and the switches have a potential 3 dB-bandwidth of 4 GHz. By the bends of rib-waveguides, both waveguides at input and output end faces were separated by 22 µm, in order to form an optical switching network and couple to optical fibers.

High-Speed Electro-Optic Analog-To-Digital (A/D) Converter

Abstract: A detailed analysis of a high-speed electrooptic guided wave analog-to-digital (A/D) converter has been performed. It is concluded that the development of converters in the 4-6 bit 1-2 GS/sec range should be feasible. Analyses are presented which detail the design considerations for the electrooptic modulator chip, the laser sampler, and the analog signal amplifier. A design plan is presented for a 6-bit 1-GS/sec converter which utilizes an array of 6 LiTaO3 interferometric waveguide modulators to perform the conversion and a frequency-doubled mode-locked Nd:YAG laser to perform the sampling of analog signals having 500 MHz bandwidths. Preliminary waveguide device results are also reported, including the successful demonstration of an interferometric modulator with a 17-dB (98%) extinction ratio.