Light-matter interaction at nanometer scale is emerging as one of the most exciting fields in nanoscience. In combination with the advanced materials synthesis technique to tailor novel low-dimensional electronic systems, new doors are open toward design and realization of nanophotonic devices with novel functionalities. Here I will present two areas that have been pursued in my research group. The first concerns optical coherent control of semiconductor quantum dots as quantum light sources for quantum information applications[1-4]. In particular, I will discuss resonant excitation of quantum emitters in a cavity which enables observation of key signatures of resonant fluorescence such as Mollow triplets and Rabi oscillations in second order photon correlations. The second topic deals with recent exciting development in metal based plasmonic platform which enables the realization of plasmonic nanolasers that break the diffraction limit[5-7]. I will discuss the first CW operation of plasmonic nanolaser with ultra-low thresholds and show that the underlying mechanism is spasing. Future perspectives of an all plasmonic photonic circuits will also be discussed.

1. Htoon, H., et al., Interplay of Rabi oscillations and quantum interference in semiconductor quantum dots. Physical Review Letters, 2002. 88(8).
2. Muller, A., et al., Resonance fluorescence from a coherently driven semiconductor quantum dot in a cavity. Physical Review Letters, 2007. 99(18).
3. Flagg, E.B., et al., Resonantly driven coherent oscillations in a solid-state quantum emitter. Nature Physics, 2009. 5(3): p. 203-207.
4. Konthasinghe, F. et. Al., “Field-Field and Photon-Photon Correlations of Light Scattered by Two Remote Two-Level InAs Quantum Dots on the Same Substrate,” Phys. Rev. Lett. 109, 267402 (2012).
5. Lu, Y.J., et al., Plasmonic Nanolaser Using Epitaxially Grown Silver Film. Science, 2012. 337(6093): p. 450-453.
6. Lu, Y.J., et al “All-Color Plasmonic Nanolasers with Ultralow Thresholds: Autotuning Mechanism for Single Mode Lasing,” NANO LETTERS 14, 4381 (2014).
7. Gwo, S. and Shih, CK. “Semiconductor plasmonic nanolasers: current status and perspectives,” Rep. Prog. Phys. 79, 086501 (2016).