Kwo Ray Chu specializes in plasma physics and, in particular, the generation of coherent electromagnetic waves via the electron cyclotron maser (ECM) interaction. The ECM is based on a stimulated cyclotron emission process involving energetic electrons in gyrational motion. It constitutes a cornerstone of relativistic electronics, a discipline that has emerged from our understanding and utilization of relativistic effects for the generation of coherent radiation from free electrons. Over a span of four decades, the ECM has undergone a remarkably successful evolution from basic research to device implementation while continuously being enriched by new physical insights. By delivering unprecedented power levels, ECMbased devices have occupied a unique position in the millimeter and submillimeter regions of the electromagnetic spectrum, and find use in numerous applications such as fusion plasma heating, advanced radars, industrial processing, materials characterization, particle acceleration, and tracking of space objects.
His academic activities include (1) Indepth mathematical formulation and physics studies of the ECM in the framework of relativistic kinetic equations, which led to the discovery of a competitive relationship between the fastwave ECM and the slowwave Weibel instabilities and provided a definitive identification of the physical mechanism responsible for the cyclotron emission observed in early experiments; (2) Development of a fully relativistic theory which led to the design and subsequent demonstration (at the University of Maryland) of a 10 GHz gyroklystron at a power level (30 MW) two orders of magnitude beyond the stateoftheart, a scheme currently explored for driving the nextgeneration accelerators; (3) Invention, fundamental studies, and demonstration of a novel Kaband gyrotron traveling wave amplifier with record performance in bandwidth, power, gain, and efficiency. This scheme has been employed in the US for the upgrade of space radars; (4) Participation in national scientific programs, in particular, the synchrotron light source project, defense electronics system research, and the establishment of Taiwan's microwave tube industry; (4) Physics of highpower terahertz radiation mechanisms (since joining NTU in 2010).

 S. H. Kao, C. C. Chiu, K. F. Pao, and K. R. Chu, “Competition between Harmonic Cyclotron Maser Interactions in the Terahertz Regime,” Phys. Rev. Lett. 107, 135101 (2011).
 C. C. Chiu, C. Y. Tsai, and S. H. Kao, K. R. Chu, L. R. Barnett and N. C. Luhmann, Jr., “Study of a HighOrderMode Gyrotron TravelingWave Amplifier,” Phys. Plasmas 17, 113104 (2010).
 L. R. Barnett, N. C. Luhmann Jr., C. C. Chiu, and K. R. Chu, “Relativistic Performance Analysis of an Advanced HighCurrentDensity Magnetron Injection Gun, ” Phys. Plasmas 16, 093111 (2009).
 C. C. Chiu, K. F. Pao, Y. C. Yan, and K. R. Chu, “Nonlinearly Driven Oscillations in the Gyrotron TravelingWave Amplifier,” Phys. Plasmas 15, 123109 (2008).
 K. F. Pao, C. T. Fan, T. H. Chang, C. C. Chiu, and K. R. Chu, “Selective Suppression of High Order Axial Modes in the Gyrotron BackwardWave Oscillator,” Phys. Plasmas 14, 053108 (2007).
 T. H. Chang, C. T. Fan, K. F. Pao, S. H. Chen, and K. R. Chu, “Stability and Tunability of the Gyrotron BackwardWave Oscillator,” Applied Phys. Lett. 90, 191501 (2007).
 K. F. Pao, T. H. Chang, C. T. Fan, S. H. Chen, C. F. Yu, and K. R. Chu, "Dynamics of Mode Competition in the Gyrotron BackwardWave Oscillator," Phys. Rev. Lett. 95, 185101 (2005).
 K. R. Chu, "The Electron Cyclotron Maser," Rev. of Modern Phys. 76, 489 (2004).
 S. H. Chen, T. H. Chang, K. F. Pao, and K. R. Chu, " Study of Axial Modes in Gyrotron BackwardWave Oscillators," Phys. Rev. Lett. 89, 268303 (2002).
 T. H. Chang, S. H. Chen, L. R. Barnett, and K. R. Chu, "Characterization of Stationary and Nonstationary Behavior of Gyrotron Backward Wave Oscillator," Phys. Rev. Lett. 87, 064802 (2001).
 S. H. Chen, K. R. Chu, and T. H. Chang, "Saturated Behavior of Gyrotron BackwardWave Oscillator," Phys. Rev. Lett. 85, 2633 (2000).
 K. R. Chu, H. Y. Chen, C. L. Hung, T. H. Chang, L. R. Barnett, S. H. Chen, and T. T. Yang, "An Ultra High Gain Gyrotron Traveling Wave Amplifier," Phys. Rev. Lett. 81, 4760 (1998).
 K. R. Chu, H. Guo, and V. L. Granatstein, "Theory of the Harmonic Multiplying
 Gyrotron Traveling Wave Amplifier," Phys. Rev. Lett. 78, 4661 (1997).
 K. R. Chu, L. R. Barnett, H. Y. Chen, S. H. Chen, Ch. Wang, Y. S. Yeh, Y. C. Tsai, T. T. Yang, and T. Y. Dawn, "Stabilization of Absolute Instabilities in the Gyrotron Travelling Wave Amplifier," Phys. Rev. Lett. 74, 1103 (1995).
 C. S. Kou, S. H. Chen, L. R. Barnett, H.Y. Chen, and K. R. Chu, "Experiments Study of an Injection Locked Gyrotron Backwave Wave Oscillator," Phys. Rev. Lett. 70, 924 (1993).
 K. R. Chu and A. T. Lin, "Harmonic Gyroresonance of Electrons in Combined Helical Wiggler and Axial Guide Magnetic Fields," Phys. Rev. Lett. 67, 3235 (1991).
 L. R. Barnett, L. H. Chang, H. Y. Chen, K. R. Chu, W. K. Lau, and C. C. Tu, "Absolute Instability Competition and Suppression in a MillimeterWave Gyrotron TravelingWave Amplifier," Phys. Rev. Lett. 63, 1062 (1989).
 K. R. Chu and A. T. Lin, "Gain and Bandwidth of the GyroTWT and CARM Amplifier," IEEE Trans. Plasma Science PS16, 90 (1988).
 K. R. Chu, V. L. Granatstein, P. E. Latham, W. Lawson, and C. D. Striffier, "A 30 MW gyroklystron Amplifier Design for High Energy Linear Accelerators," IEEE Trans. Plasma Science PS13, 424 (1985).
 Y. Carmel, K. R. Chu, M. E. Read, A. K. Ganguly, D. Dialetis, R. Seeley, J. S. Levine and V. L. Granatstein, "Realization of a Stable and Highly Efficient Gyrotron for Controlled Fusion Research,'' Phys. Rev. Lett. 50, 112 (1983).
 Y. Y. Lau and K. R. Chu, "Electron Cyclotron Maser Instability Driven by Loss Cone Distribution,” Phys. Rev. Lett. 50, 243 (1983).
 H. Guo, L. Chen, H. Keren, J. L. Hirshfield, S. Y. Park, and K. R. Chu, "Measurement of Gain for Slow Cyclotron Waves on an Annular Electron Beam," Phys. Rev. Lett. 49, 730 (1982).
 R. M. Gilgenbach et al. (15 authors), "Heating at the Electron Cyclotron Frequency in the SXB Tokamak," Phys. Rev. Lett. 44, 647 (1980).
 K. R. Chu and J. L. Hirshfield, "Comparative Study of the Azimuthal and Axial Bunching Mechanisms in Electromagnetic Cyclotron Instabilities," Phys. Fluids 21, 461 (1978).
 K. R. Chu, "Theory of Electron Cyclotron Maser Interaction in a Cavity at the Harmonic Frequencies," Phys. Fluids 21, 2354 (1978).
 K. R. Chu and R. W. Clark, "Dynamical Model for Magnetic Signal Interpretation in Relativistic Electron Beam Heated Plasmas," Phys. Rev. Lett. 38, 704 (1977).
 W. M. Manheimer, K. R. Chu, E. Ott and J. P. Boris, "Marginal Stability Calculation of Electron Temperature Profiles in Tokamaks," Phys. Rev. Lett. 37, 286 (1975).
 K. R. Chu, R. W. Clark, M. Lampe, P. C. Liewer and W. M. Manheimer, "Ion Heating by Expansion of BeamHeated Plasma," Phys. Rev. Lett. 35, 94 (1975).
 C. A. Kapetanakos, W. M. Black, and K. R. Chu, "Plasma Heating by a Rotating Relativistic Electron Beam," Phys. Rev. Lett. 34, 1156 (1975).
 K. R. Chu, N. Rostoker, "Interaction of a Rotational Relativistic Electron Beam with a Magnetized Plasma," Phys. Fluids 17, 813 (1974).
 K. R. Chu, N. Rostoker, "Relativistic Electron Beam Neutralization in a Dense Magnetized Plasma," Phys. Fluids 16, 1472 (1973).
