Research

Nanophotonics & optical micro-resonator

Nano-optical fiber and solid-state microsphere resonator

Nano-optical fiber possessing a very small diameter comparable to optical wavelength is coupled to solid-state silica microsphere whose size is 10-100 um. This taper-fiber-coupled microsphere resonator may work as a quantum phase gate (QPG), when we embed atoms and quantum dots into the resonator. The solid-state QPG will work with much higher efficiency than conventional QPGs. We believe that the solid-state QPG is a key to the realization of quantum information technology.

Fig.06

  • [1] A. Chiba, H. Fujiwara, J. Hotta, S. Takeuchi and K. Sasaki, “Resonant frequency control of a microspherical cavity by temperature adjustment”, Jpn. J. Appl. Phys. 43, 6138-6141 (2004).
  • [2] A. Chiba, H. Fujiwara, J. Hotta, S. Takeuchi and K. Sasaki, “Fano resonance in a multimode tapered fiber coupled with a microspherical cavity”, Appl. Phys. Lett. 86, 261106/1-3 (2005).
  • [3] H. Konishi, H. Fujiwara, S. Takeuchi and K. Sasaki, “Polarization-discriminated spectra of a fiber-microsphere system”, Appl. Phys. Lett. 89, 121107/1-3 (2006).

Generation of non-classical light from a single molecule or single quantum dot.

Semiconductor quantum dots (QDs) having their size of 100-101 nm show large optical nonlinearity and atom-like emission. In particular, core-shell-type CdSe/ZnS QDs have promising optical characters for device applications. Emission wavelength from these dots can be controlled by changing their size, for example. Their emission also shows anti-bunting behavior at room temperature. We use this type of single QDs for the development of highly efficient single photon sources and nonlinear quantum devices.

Fig.07

Controlling the emissions from atoms in microsphere resonator

The taper fiber allows us to efficiently inject light into the microsphere resonator, in which very high quality factor is achieved. Using this taper-fiber-coupled microsphere resonator, we demonstrated the lasing of Er & P sol-gel glass layer on the microsphere. The thickness of the gain layer is ultimately thin on the order of ~ 100 nm. Furthermore, we have shown that the coupling efficiency of spontaneous emission into the modes of microsphere cavity can be greatly enhanced by controlling the depth of the gain layer in the sphere.

Fig.08

  • [1] Hideaki Takashima, Hideki Fujiwara, Shigeki Takeuchi, Keiji Sasaki, and Masahide Takahashi, “Control of spontaneous emission coupling factor in fiber-coupled microsphere resonators”, Appl. Phys. Lett. 92, 071115 (2008).
  • [2] Hideaki Takashima, Hideki Fujiwara, Shigeki Takeuchi, Keiji Sasaki, and Masahide Takahashi, “Fiber-microsphere laser with a submicrometer sol-gel silica glass layer codoped with erbium, aluminum, and phosphorus”, Appl. Phys. Lett. 90, 101103 (2007).

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The Institute of Scientific and Industrial Research (ISIR),
Osaka University, Quantum Information Photonics Laboratory (Takeuchi Lab.),
8-1 Mihogaoka, Ibaraki, Osaka, JAPAN, 567-0047
TEL:+81-(0)6-6877-6727, E-Mail:takeuchi@sanken.osaka-u.ac.jp
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