Saifeng Zhang, Hongxing Dong, Wei Xie, Liaoxin Sun, Xuechu Shen, Zhanghai Chen

1. Motivation The strong coupling of exciton-photon (i. e. exciton polariton) has been observed in various semiconductor optical cavities [1-3] and has attracted tremendous attention in the past decades due to its potential in nano-photonics and polaritonics application. For practical device application, tunablity of the exciton-photon coupling is crucial. So far, several complex techniques such as cavity size control, temperature, external electric or magnetic field etc., have been applied to tune the exciton-photon interaction [4-5]. However, the response of these techniques is slow and the required field strength is large. A fast and easily controllable tuning method of strong coupling is needed for practical device application. (a) TE92 SEM of ZnO microrod Cross section: hexagon 0.2mA 0.25mA 0mA 0.1mA 0.15mA 0.28mA Electrode pattern (b) (c) The polariton effect within ZnO whispering gallery microcavity tuned by current induced thermal effect Saifeng Zhang, Hongxing Dong, Wei Xie, Liaoxin Sun, Xuechu Shen, Zhanghai Chen State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China Experiment and discussion Fig. 1 (a) the dispersion of exciton polariton under different current. (b) the redshift of lower polariton branches (different order with polarization TE) (c) the temperature corresponding to current measured by Raman spectra • Conclusion: • The redshift of polariton mode can be as large as ~40 meV when we adjust current in ZnO microrod. It can be used as a promising technique to tune strong coupling between exciton and photon in semiconductors. • The Stark effect is excluded and this redshift is attributed to current induced thermal effect. With a simple heat conduction model, we found that the tuning speed is fast (~230 K in 0.3 ms). • The temperature was measured by Raman spectra. It is demonstrated that the strong coupling is preserved up to ~550 K. Heat conduction model Heat dissipation power: (rough estimation) References: [1] Lambert K. van Vugt et al., Phys. Rev. Lett. 97, 147401 (2006). [2] Chris Sturm et al., New J. Phys. 11, 073044 (2009). [3] Liaoxin Sun et al., Phys. Rev. Lett. 100, 156403 (2008). [4] T. A. Fisher et al., Phys. Rev. B 51, 2600 (1995) [5] Tsintzos, S. I. et al., Nature 453, 372-375 (2008) Heat production power: In a very short time, for instance, 0.3 ms, the change of temperature can reach up to 230 K. The thermal equilibriumcan be establishedin this time scale.