A hollow bottle-like microresonator (BLMR) with ultra-high quality factor is fabricated from a microcapillary with nearly parabolic profile. At 1.55 µm pumping, degenerate four-wave mixing can be observed for a BLMR of diameter 102 µm. The parabolic profile of the BLMR guarantees a nearly zero waveguide dispersion, which is theoretically discussed in detail. From the simulation, at 1.55 µm wavelength in such a BLMR, the fundamental bottle mode is in the anomalous dispersion regime, whilst the ordinary whispering gallery mode (WGM) confined at the center of the BLMR is in the normal dispersion regime. Experimentally, no degenerate FWM is observed for the WGM selected by positioning the coupling tapered fiber in the same BLMR. Furthermore, dispersion tuning is briefly discussed. As the work predicted, the BLMR shows promise for the implementation of sparsely distributed, widely spanned frequency combs at the telecommunication wavelength.
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 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 $1.55~\mathrm{\mu m}$ and $780~\mathrm{nm}$. 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
$780~\mathrm{nm}$. 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
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.
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