Low mode volume slotted photonic crystal single nanobeam cavity
  We present and experimentally demonstrate a slotted photonic crystal single nanobeam cavity in silicon. The slot geometry is exploited to achieve ultra-small effective mode volumes, ~0.025({\lambda}/n)^3, more than an order of magnitude smaller than traditional nanobeam cavities. A continuous slot and a tapered photonic crystal design are implemented to achieve experimental quality factors near 10^4. This device structure offers a unique platform for achieving enhanced light-matter interactions and could be used to benefit a variety of applications including non-linear optics, cavity quantum electro-dynamics, sensing, optical modulation, and nano-optomechanics. 
Judson D. Ryckman and S. M. Weiss
physics.optics