Naoto Kumagai

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We demonstrate room temperature continuous-wave laser operation at 1.3 mum in a photonic crystal nanocavity with InAs/GaAs self-assembled quantum dots by optical pumping. By analyzing a coupled rate equation and the experimental light-light characteristic plot, we evaluate the spontaneous emission coupling factor of the laser to be ~ 0.22. Three-dimensional(More)
We report on newly-designed H1-type photonic crystal (PhC) nanocavities that simultaneously exhibit high Q factors, small mode volumes, and high external coupling efficiencies (η([perpendicular])) of light radiated above the PhC membrane. Dipole modes of the H1 PhC nanocavities, which are doubly-degenerate and orthogonally-polarized in theory, are(More)
Spontaneous two-photon emission from a solid-state single quantum emitter is observed. We investigated photoluminescence from the neutral biexciton in a single semiconductor quantum dot coupled with a high Q photonic crystal nanocavity. When the cavity is resonant to the half energy of the biexciton, the strong vacuum field in the cavity inspires the(More)
We report the observation of the vacuum Rabi splitting of a single quantum emitter by measuring its direct spontaneous emission into free space. We use a semiconductor quantum dot inside a photonic crystal nanocavity, in conjunction with an appropriate cavity design and filtering with a polarizer and an aperture, enabling the extraction of the inherently(More)
We investigate the dependence of quality factor Q of dipole modes in photonic crystal H1-defect nanocavity on the slab thickness and observe an increase of Q even after closing of the photonic bandgap both in numerical simulation and experimentation. This counter intuitive behavior results from the weak coupling between the cavity mode and the 2nd-guided(More)
An enhanced optical Stark shift in a single quantum dot is demonstrated using a newly-designed H1-type photonic crystal nanocavity. A 70μeV shift is observed at 450nW; 110-times lower than excitation powers reported in the literature.
Gain characteristics of antimony-mediated high-density InAs quantum-dot lasers were evaluated. For the lasers with 5 and 10 quantum dot layers, 88% and 39% increase in the maximum modal gain, respectively, was obtained compared with that of conventional InAs quantum dots.