  Photonic crystal (PhC) nanocavities have demonstrated unique capabilities in
terms of light confinement and manipulation. As such, they are becoming
attractive for the design of novel resonance-based photonic integrated circuits
(PICs). Here two essential challenges arise however - how to realize
ultrahigh-Q PhC cavities using standard fabrication processes compatible with
large volume fabrication, and how to efficiently integrate them with other
standard building blocks, available in exiting PIC platforms. In this work, we
demonstrate ultrahigh-Q 1D PhC nanocavities fabricated on a 300 mm SOI wafer by
optical lithography, with a record Q factor of up to 0.84 million. Moreover, we
show efficient mode management in those oxide embedded cavities by coupling
them with an access waveguide and realize two critical components: notch
filters and narrow-band reflectors. In particular, they allow both
single-wavelength and multi-wavelength operation, at the desired resonant
wavelengths, while suppressing all other wavelengths over a broad wavelength
range (>100 nm). Compared to traditional cavities, this offers a fantastic
strategy for implementing resonances precisely in PIC designs with more freedom
in terms of wavelength selectivity and the control of mode number. Given their
compatibility with optical lithography and compact footprint, the realized 1D
PhC nanocavities will be of profound significance for designing compact and
novel resonance-based photonic components on large scale.
