Physical Optics and Electronics Group
Prof. Rajeev Ram

Major Research Themes:


The goal of this work has been to exploit the ability of electrons to transport energy. Electronic energy transport can be used to develop electronics that cool under operation as well as to generate power from waste heat.


The lab has developed a high-resolution thermal imaging system capable of 200 nm spatial resolution and 10 mK temperature resolution. A high-temperature Z-meter capable of simultaneously measuring electrical conductivity, thermal conductivity, and Seebeck coefficient at temperatures up to 800 C has also been developed.


Jin Xue, and Zheng Li.



  1. Duanni Huang, Parthiban Santhanam, and Rajeev J. Ram. ” Low-Power Communication with a Photonic Heat
    Pump.” Optics Express, 22, S7, (2014): A1650-58. [PDF]

  2. Gray, Jr., Dodd J., Parthiban Santhanam, and Rajeev J. Ram. “Design for Enhanced Thermo-Electric Pumping in Light Emitting Diodes.” Applied Physics Letters 103.12 (2013): 123503. [PDF]

  3. Santhanam, Parthiban, Duanni Huang, Rajeev J. Ram, Maxim A. Remennyi, and Boris A. Matveev. “Room Temperature Thermo-Electric Pumping in Mid-Infrared Light-Emitting Diodes.” Applied Physics Letters 103.18 (2013): 183513. [PDF]

  4. Amatya, R., P. M. Mayer, and R. J. Ram. “High Temperature Z-meter Setup for Characterizing Thermoelectric Material Under Large Temperature Gradient.” Review of Scientific Instruments 83.7 (2012): 075117. [PDF]
  5. Chen, S. C., S. L. Lee, H. Lo, Y. J. Hung, K. Y. Lee, C. G. Tu, Y. T. Pan and R. J. Ram. “Silicon Platform with Vertically Aligned Carbon Nanotubes for Enhancing Thermal Conduction in Hybrid Optoelectronic Integration.” IEEE Trans. Compon. Packag. Manuf. Technol. 2.7 (2012): 1128-34. [PDF]
  6. Santhanam, Parthiban, Dodd Joseph Gray, Jr., and Rajeev J. Ram. “Thermoelectrically Pumped Light-Emitting Diodes Operating above Unity Efficiency.” Phys. Rev. Lett. 108 (2012): 097403. [PDF]

  7. Bahk, Je-Hyeong, Parthiban Santhanam, Zhixi Bian, Rajeev Ram, and Ali Shakouri. “Resonant Carrier Scattering by Core-Shell Nanoparticles for Thermoelectric Power Factor Enhancement.” Applied Physics Letters 100 (2012). [PDF]
  8. Lo, Hsinyi, and Rajeev J. Ram. “Submicron Mapping of Thermal Conductivity of Thermoelectric Thin Films.” Journal of Electronic Materials 41.6 (2012): 1332-6. [PDF]

  9. Settaluri, K. T., H. Lo, and R. J. Ram. “Thin Thermoelectric Generator System for Body Energy Harvesting.” Journal of Electronic Materials 41.6 (2012): 984-8. [PDF]
  10. Amatya, Reja, and Rajeev J. Ram. “Trend for Thermoelectric Materials and Their Earth Abundance.” Journal of Electronic Materials 41.6 (2012): 1332-6. [PDF]
  11. Bahk, J., Z. Bian, M. Zebarjadi, P. Santhanam, R. J. Ram, and A. Shakouri. “Thermoelectric Power Factor Enhancement by Ionized Nanoparticle Scattering.” Applied Physics Letters 99 (2011). [PDF]
  12. Amatya, R., and R. J. Ram. “Solar Thermoelectric Generator for Micropower Applications.” Journal of Electronic Materials 39.9 (2010): 1735. [PDF]
  13. Summers, J. A., M. Farzaneh, R. J. Ram, and J. A. Hudgings. “Thermal and Optical Characterization of Photonic Integrated Circuits by Thermoreflectance Microscopy.” IEEE Journal of Quantum Electronics 46.1 (2010): 3-10. [PDF]
  14. Mayer, P., D. Lueerssen, R. J. Ram, and J. Hudgings. “Theoretical and Experimental Investigation of the Resolution and Dynamic Range of CCD-Based Thermoreflectance Imaging.” Journal of the Optical Society of America A 24.4 (2007): 1156-63. [PDF]
  15. Mayer, P., and R. J. Ram. “Optimization of Heat-sink Limited Thermoelectric Generators.” Nanoscale and Microscale Thermophysical Engineering 10.2 (2006): 143-55. [PDF]
  16. Mohseni, K., A. Shakouri., and R. J. Ram. “Electron Vortices in Semiconductor Devices.” Physics of Fluids 17 (2005): 100602. [PDF]
  17. Lyeo, H., A. A. Khajetoorians, L. Shi, K. P. Pipe, R. J. Ram, A. Shakouri, and C. K. Shih. “Profiling the Thermoelectric Power of Semiconductor Junctions with Nanometer Resolution.” Science 303 (2004): 816-8. [PDF]
  18. Luerssen, D., R. J. Ram, A. Hohl-AbiChedid, E. Clausen, Jr., and J. A. Hudgings. “Thermal Profiling: Locating the Onset of Gain Saturation in Semiconductor Optical Amplifiers.” IEEE Photon. Technol. Lett. 16.7 (2004): 1625-7. [PDF]
  19. Hudgings, J. A., K. P. Pipe, and R. J. Ram. “Thermal Profiling for Optical Characterization of Waveguide Devices.” Applied Physics Letters 83.19 (2003): 3882-4. [PDF]
  20. Pipe, K. P., and R. J. Ram. “Comprehensive Heat Exchange Model for a Semiconductor Laser Diode.” IEEE Photon. Technol. Lett. 15.4 (2003): 504-6. [PDF]
  21. Pipe, K. P., and R. J. Ram. “Bias-Dependent Peltier Coefficient and Internal Cooling in Bipolar Devices.” Physical Review B 66 (2002): 125316. [PDF]



  1. J. Xue, Z. Li, R. J. Ram, "Irreversible Thermodynamic Bound for the Efficiency of Light-Emitting Diodes," American Physical Society, Physical Review Applied, 8, 014017 (2017) DOI: 10.1103/PhysRevApplied.8.014017 [PDF]
  2. D. Huang, P. Santhanam, and R. J. Ram, "Low-Power Communication with a Photonic Heat Pump," Optics Express, 22, S7 (2014): A1650-58, [PDF]
  3. D. Gray, Jr, P. Santhanam, R. J. Ram, "Design for Enhanced Thermo-Electric Pumping in Light Emitting Diodes," Applied Physics Letters 103.12 (2013): 123503, DOI: 10.1063/1.4821266 [PDF]