Progress on the fabrication of ultrahigh-Q photonic-crystal nanocavities (PhC-NCs) has revealed the prospect for new applications including silicon Raman lasers that require a strong confinement of light. Among various PhC-NCs, the highest Q has been recorded with silicon. On the other hand, microcavity is one of the basic building blocks in silicon photonics. However, the fusion between PhC-NCs and silicon photonics has yet to be exploited, since PhC-NCs are usually fabricated with electron-beam lithography and require an air-bridge structure. Here we show that a 2D-PhC-NC fabricated with deep-UV photolithography on a silica-clad silicon-on-insulator (SOI) structure will exhibit a high-Q of 2.2 × 105 with a mode-volume of ~1.7(λ/n)3. This is the highest Q demonstrated with photolithography. We also show that this device exhibits an efficient thermal diffusion and enables high-speed switching. The demonstration of the photolithographic fabrication of high-Q silica-clad PhC-NCs will open possibility for mass-manufacturing and boost the fusion between silicon photonics and CMOS devices.

We design scalable all-optical logic gates that operate with the same input and output wavelength. We demonstrated the operation by using coupled mode equations, and investigated the impact of input power fluctuations and fabrication errors. We found that a wavelength fluctuation 0.3 times greater than the resonant wavelength width will degrade the operation of the system. Stronger coupling increases the wavelength tolerance. As regards coupling coefficient fluctuation, we found that the system is error-free when the fabrication precision is better than ± 5 nm. This study provides information on the required input power stability and tolerable fabrication errors of a scalable system, which moves the numerical study closer to practical realization.

We developed a method that can accurately calculate the theoretical quality factor (Q) of a two-dimensional photonic crystal slab nanocavity at a very high speed. Because our method is based on a direct calculation of the out-of-slab radiation loss rate, it does not suffer from in-plane loss, and this allows us to obtain the same Q with 0.18 times less calculation volume. In addition, we can obtain the Q immediately after finishing the cavity excitation, because our method uses only a snapshot of the wavevector space distribution of the resonant mode in contrast to the conventional method, where we need to fit the electro-magnetic field with an exponential decay that requires a relatively long data set. For a width-modulated line defect cavity that has a Q of 8.5 × 10(7) we obtained the same value as with a conventional method but with 94% less computation time.

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We developed a method for calculating the Q-factor of a 2D photonic crystal nanocavity directly from the in-plane wavevector distribution of the cavity mode. A high-Q of >10 7 was obtained with high accuracy and speed. OCIS codes: (230.5298) Photonic crystals; (230.5750) Resonators IntroductionThe theoretical quality factor (Q) of a two-dimensional (2D) photonic crystal (PhC) nanocavity is usually dominated by the out-of-slab radiation loss. Since a higher experimental Q is obtained with a cavity with a better design (i.e. a higher theoretical Q), it is important to for us to undertake fast and accurate numerical studies. Q is usually determined with a three-dimensional finite-difference time-domain (3D-FDTD) calculation. Since the theoretical Q value is now higher than 10 7 , a long calculation time is required to obtain the cavity Q accurately. The theoretical Q is usually obtained by calculating the total energy in the calculation area at every calculation step and observing the field decay.In this work, we developed a new method that allows us to calculate Q by using a 2D mode profile at the center of the slab, without the need to conduct a time-consuming 3D energy calculation. Although we still use 3D-FDTD, we greatly shorten the calculation time by more than 4 times, because we can use a much smaller calculation area. More importantly, as we show later in this work, we obtain a highly accurate Q with our method, even when we finish the calculation immediately after the light excitation.