Optics and Quantum Electronics

Contains reports on ten research projects.Joint Services Electronics Program (Contract DAALO3-86-K-0002)National Science Foundation (Grant ECS 83-05448)National Science Foundation (Grant ECS 83-10718)National Science Foundation (Grant ECS 82-11650)National Science Foundation (Grant ECS 84-13178)National Science Foundation (Grant ECS 85-52701)US Air Force - Office of Scientific Research (Contract AFOSR-85-0213)National Institutes of Health (Contract 5-RO1-GM35459)U.S. Navy - Office of Naval Research (Contract N00014-86-K-0117

III-V waveguides and couplers for integrated optics

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 1987Bibliography: leaves 180-183.by Nadir Dagli.Ph. D.Ph. D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Scienc

0.77-V drive voltage electro-optic modulator with bandwidth exceeding 67 GHz.

A 0.77-V drive voltage (V(π)) electro-optic modulator with bandwidth exceeding 67 GHz is described. Modulator is a compound semiconductor device fabricated using substrate removal technology. This allows placement of metal electrodes on both sides of an optical waveguide containing a p-i-n diode. Hence ohmic losses are reduced significantly. Electrode gap is essentially the same as i layer thickness, which can be kept very uniform and small. Waveguide core also contains a MQW, which improves electro-optic efficiency. Lack of p doping in the waveguide and large detuning between MQW absorption peak and operating wavelength keep the propagation loss low. Large size of the waveguide also helps to keep coupling loss low. Modulator is designed as a traveling wave device using the loaded line approach, which is used for velocity matching. Combination of these approaches yields a device with the lowest V(π) and widest bandwidth

0.77-V drive voltage electro-optic modulator with bandwidth exceeding 67 GHz.

A 0.77-V drive voltage (V(π)) electro-optic modulator with bandwidth exceeding 67 GHz is described. Modulator is a compound semiconductor device fabricated using substrate removal technology. This allows placement of metal electrodes on both sides of an optical waveguide containing a p-i-n diode. Hence ohmic losses are reduced significantly. Electrode gap is essentially the same as i layer thickness, which can be kept very uniform and small. Waveguide core also contains a MQW, which improves electro-optic efficiency. Lack of p doping in the waveguide and large detuning between MQW absorption peak and operating wavelength keep the propagation loss low. Large size of the waveguide also helps to keep coupling loss low. Modulator is designed as a traveling wave device using the loaded line approach, which is used for velocity matching. Combination of these approaches yields a device with the lowest V(π) and widest bandwidth

Novel T-rail electrodes for substrate removed low-voltage high-speed GaAs/AlGaAs electrooptic modulators

A novel traveling-wave electrode utilizing capacitively loaded T-rail elements was developed for low-voltage high-speed substrate-removed GaAs/AlGaAs electrooptic modulators. Electrodes with varying dimensions were fabricated and characterized. Electrode phase velocity, characteristic impedance, loss coefficient, and capacitive loading were extracted from the measured s-parameters up to 40 GHz. Electrode was also simulated using a finite-element solver. The measured and calculated electrode capacitance values were found to be in excellent agreement, showing that the electrode can be precisely designed. Approaches were outlined to provide a group velocity-matched very high-speed modulator electrode suitable for a low drive-voltage substrate-removed GaAs/AlGaAs electro-optic modulator