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Prelims 2016 Prof. Candler 1) Have student explain his/her research area and background. Ask questions based on this. 2) Show your tuning fork resonator. It rings at some frequency, f, described by 𝑥 = 𝑥! 𝑒 !!!"# . Exactly how would you expect the resonant frequency to change as you scaled the device down? Perform same analysis for LC resonator and compare the two, focusing on fundamental similarities of these two systems PhD Preliminary Examination 2016 Professor Frank Chang PhD Preliminary Examination 2016 Professor Frank Chang PhD Preliminary Examination 2016 Professor Frank Chang Prof. Iyer 2016 Prelim Exam Questions: 1. Fig 1 below shows a tiled view of Samsung’s FINFET process in 14 nm ’ Let’s discuss this picture. a. b. c. d. e. f. g. h. Can you point out where the fin is its direction? Where are the source-drain contacts? Where are the gate contacts? Is the FINFET a symmetric device? Can you say something about the gate material? Can you draw a model for the FINFET? Why is the FINFET an “ideal device”? What are the key drawbacks of the FINFET? 2016 PhD Preliminary Exam Prof. Joshi Set A 1. 2. 3. 4. What is a plane wave? What do we mean by a beat wave? What do we mean by an amplitude modulated waveform? What is the frequency spectrum of the waveform? Set B 1. Write electric field of a laser that is Gaussian in time. 2. What does the frequency spectrum of this pulse look like? 3. How do you produce a “chirped” pulse? Set C 1. What is the physical origin of permittivity and permeability? 2. If we had hydrogen gas, water vapor, and CO2 gas and applied an electric field, what would be the order of polarization produced in each? Set D 1. What is a plane em wave? 2. What do we mean by amplitude modulated wave? 3. Does amplitude modulation cause frequency broadening? 2016 Ph.D. Prelim Questions J.M. Liu Your Name: Questions: 1. Among the four fields E , D , B , and H of an electromagnetic wave, which ones are always perpendicular to the wavevector k in any medium and in any spectral region? For each field that is not always perpendicular to k , discuss the situations when it can be perpendicular to k and give a situation when it is not perpendicular to k . Explain briefly. 2. What are the conditions for laser oscillation? Describe the essential requirements that you must meet to construct a working laser oscillator. What changes in its characteristics do you expect to see when a laser starts to oscillate above threshold? 3. Silicon is the most important electronic material, but it has limitations in photonic applications. Describe and explain the possibilities or limitations of using silicon to construct a Pockels cell, a Faraday rotator, an acousto-optic modulator, an LED, a laser, or a photodetector. PhD Preliminary Examination 2016 Professor Ozcan PhD Preliminary Examination 2016 Professor Rahmat-Samii PhD Preliminary Examination 2016 Professor K. Wang Preliminary Exam 2016 Professor Y. Ethan Wang Derive the Quality factor of a quarter waves transmission line resonator that has a characteristic impedance Z0, loaded with a resistor R (R<<Z0). PhD Preliminary Examination 2016 Professor Williams Prelims 2016 Professor Williams What is the Quality Factor Q? Give an example. Estimate the quality factor of a cavity mode of a Fabry-Perot optical cavity (air/dielectric/air). The thickness of the dielectric slab is 0.5 mm, the index of refraction is n=9, the wavelength of light is 1μm. PhD Preliminary Examination 2016 Professor Woo PhD Preliminary Examination 2016 Professor Woo PhD Preliminary Examination 2016 Professor Woo