Showing papers on "Extinction ratio published in 1975"

GaAs electro‐optic directional‐coupler switch

Abstract: We report the fabrication and testing of a GaAs electro‐optic directional‐coupler (EDC) switch in which the fraction of light coupled from one waveguide channel to the other can be controlled by an applied electric field Ninety‐five percent amplitude switching and a maximum extinction ratio of 13 dB have been observed in an EDC switch, having a minimum 3‐dB bandwidth of ≳100 MHz and a drive power per unit bandwidth of <180 μW/MHz

Electro-optic light modulator with branched ridge waveguide

Abstract: A light modulator based on an electro‐optic phase modulation and an optical interference of Mach‐Zehnder type has been demonstrated. The modulator is constructed monolithically with a branching ridged optical waveguide on TiO2‐diffused LiNbO3. The half‐wave voltage is 19 V and the extinction ratio is 34%.

Electro‐optic amplitude modulation using three‐dimensional LiNbO3 waveguide fabricated by TiO2 diffusion

Abstract: An almost single‐mode waveguiding layer has been fabricated by thermal diffusion of TiO2 into LiNbO3. The refractive‐index change in the layer is 2–3×10−3 for both ne and no, and the propagation loss is 0.7–0.8 dB/cm. The electro‐optic coefficients are found to be nearly equal to those of the bulk crystal. An amplitude modulation has been made with a stripe waveguide 10 μm wide and planar electrodes. The half‐wave voltage is 17 V and the maximum extinction ratio is 12 dB.

Laser‐initiated krytron‐switched Blumlein structure for pulse selection

Abstract: A method is described for the selection of a mode‐locked pulse from a laser by the use of a laser‐initiated krytron‐switched Blumlein structure that replaces the usual high voltage spark gap. The main features are an all electronic circuit coupled to a longitudinal mode KD*P Pockels cell that has a fast risetime and high extinction ratio. The result is an inexpensive, noise‐free pulse selector that provides a stable source of switched out pulses.

Modulation and Switching of Light in Dielectric Waveguides

Abstract: In this chapter, we will discuss methods of electronically controlling the flow of light in optical waveguides. We will restrict our attention to devices that may be called either modulators or switches. Some of these devices are capable of performing both functions.

Prepulse extinction-ratio measurements on a CO 2 -laser system

Abstract: Prepulse extinction-ratio measurements performed on two pulse-selection systems at the input and the output of a CO 2 -amplifier chain are described.

Residual phase corrugation in total internal reflection diffraction devices

Abstract: A study is made of electro-optic total-internal-reflection diffraction device modulator electroding. This can cause reflection phase inequalities which can reduce transmission (zero order) and degrade the extinction ratio. Al, Cu, Au, and Cr electrodes are considered and Al/Cr appears the optimum choice for LiNbO3 devices. A practical LiNbO3/Cr device realization is shown to exhibit a 0.6% insertion loss contribution due to this effect and agrees with theory. Analysis shows that a reflection phase mismatch of 16 degrees adds to insertion loss by 2%, but at 28 degrees (mismatch) this addition rises to 6%. An extinction ratio >100:1 was noted.

Faraday rotation, optical isolation and modulation at 10.6 μm using hot-pressed CdCr2S4 and CoCr2S4

Abstract: Measurements performed on hot-pressed samples of ferromagnetic CdCr2S4 and ferrimagnetic CoCr2S4 indicate that they would be useful as optical isolators and modulators for CO2 lasers at 10.6 μm. Based on the Faraday effect, large aperture devices could be fabricated which would operate under modest cooling and drive power requirements. The various figures of merit needed to evaluate the performance of these materials as isolators and modulators have been determined optically with a low power CO2 laser. D.C. applied magnetic fields were used to determine the variations in measured Faraday rotation as a function of sample thickness. Figures of merit pertinent to isolation were also obtained, such as the passive extinction ratio and forward to backward transmitted energy ratio. A.C. applied magnetic fields were used to determine the frequency response of the materials, their modulation depths, and drive powers up to 100 kHz. Short duration pulses were used to analyze higher frequency behavior.

Passive anti-return device for high power ruby laser

Abstract: The high power ruby lasers with an amplifier chain must be protected of the light returns towards the oscillator. After description of the most used devices, we show that it is possible to use a process mixing an saturable absorber and a prism polarizer followed by a plate retarder. We are leading to observe again the transmission curves of saturable glasses RG715 type from Schott, versus lightning and time. The transmission factors derived from this studies are compared to be measures done with a 80 MW ruby laser. With anti-reflection coatings on the optical elements, the transmission factor of the direct laser wave is 75% whereas the extinction ratio of the return wave is 2.10-5.