Yuta Ooka

CMOS compatible high-Q photonic crystal nanocavity fabricated with photolithography on silicon photonic platform

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.

Degenerate four-wave mixing in a silica hollow bottle-like microresonator

A hollow, bottle-like microresonator (BLMR) was fabricated from a microcapillary with a nearly parabolic profile. From simulations at 1.55 μm the fundamental bottle mode is shown to be in the anomalous dispersion regime, while the conventional whispering gallery mode, confined to the center of the BLMR, is in the normal dispersion regime. Therefore, we have experimentally shown that, for a BLMR with a diameter of 102 um, degenerate four-wave mixing can only be observed by judicious selection of the tapered fiber coupling position. Dispersion tuning in such a system is also briefly discussed theoretically. BLMRs are promising devices for the implementation of sparsely distributed, widely spanned frequency combs at the telecommunications C-band.

Raman lasing in a hollow, bottle-like microresonator

We report on the fabrication of an ultrahigh quality factor, bottle-like microresonator from a microcapillary, and the realization of Raman lasing therein at pump wavelengths of

Ultrasmall in-plane photonic crystal demultiplexers fabricated with photolithography

1.55~\mathrm{\mu m}

Compact resonant electro-optic modulator using randomness of a photonic crystal waveguide.

and

High-Q coupled resonances on a PhC waveguide using a tapered nanofiber with high coupling efficiency.

780~\mathrm{nm}

SiO 2 clad active and passive photonic crystal nanocavity devices fabricated with photolithography: Toward future mass production of photonic crystal nanocavity devices

. The dependence of the Raman laser threshold on mode volume is investigated. The mode volume of the fundamental bottle mode is calculated and compared with that of a microsphere. Third-order cascaded Raman lasing was observed when pumped at

Robust CMOS compatible photonic crystal nanocavity and DEMUX filter

780~\mathrm{nm}

Recent progress on high-Q photonic crystal nanocavities: Photolithographic fabrication and reconfigurable system

. In principle, Raman lasing in a hollow bottle-like microresonator can be used in sensing applications. As an example, we briefly discuss the possibility of a high dynamic range, high resolution aerostatic pressure sensor.

Fiber-coupled photonic crystal nanocavity for reconfigurable formation of coupled cavity system

We demonstrate ultrasmall demultiplexers based on photolithographic photonic crystals. The footprint of the demultiplexers is 110 μm2 per channel. Our in-plane demultiplexers are clad with silica, which makes them stable and easy to integrate with other silicon photonic devices. We describe two types of demultiplexers with spacings of 136 and 267 GHz between channels for application to dense wavelength division multiplexing. Integrated titanium nitride heaters allow us to precisely control the channel wavelength. We report a 2.5 Gbps transmittance experiment with sufficiently small crosstalk and discuss ways of achieving even lower crosstalk between channels.