Fabrication of a nanofiber Bragg cavity with high quality factor using a focused helium ion beam

Nanofiber Bragg cavities (NFBCs) are solid-state microcavities fabricated in an optical tapered fiber. NFBCs are promising candidates as a platform for photonic quantum information devices due to their small mode volume, ultra-high coupling efficiencies, and ultra-wide tunability. However, the quality (Q) factor has been limited to be approximately 250, which may be due to limitations in the fabrication process. Here we report high Q NFBCs fabricated using a focused helium ion beam. Whenan NFBC with grooves of 640 periods is fabricated, the Q factor is over 4170, which is more than 16 times larger than that previously fabricated using a focused gallium ion beam

Non-contact detection of nanoscale structures using optical nanofiber

The detection of nanoscale structure/material property in a wide observation area is becoming very important in various application fields. However, it is difficult to utilize current optical technologies. Toward the realization of novel alternative, we have investigated a new optical sensing method using an optical nanofiber. When the nanofiber vertically approached a glass prism with a partial gold film, the material differences between the glass and the gold were detected as a transmittance difference of 6% with a vertical resolution of 9.6 nm. The nanofiber was also scanned 100 nm above an artificial small protruding object with a width of 240 nm. The object was detected with a horizontal resolution of 630 nm, which was less than the wavelength of the probe light