47 research outputs found
Dynamic release of trapped light from an ultrahigh-Q nanocavity via adiabatic frequency tuning
Adiabatic frequency shifting is demonstrated by tuning an ultrahigh-Q
photonic crystal nanocavity dynamically. By resolving the output temporally and
spectrally, we showed that the frequency of the light in the cavity follows the
cavity resonance shift and remains in a single mode throughout the process.
This confirmed unambiguously that the frequency shift results from the
adiabatic tuning. We have employed this process to achieve the dynamic release
of a trapped light from an ultrahigh-Q cavity and thus generate a short pulse.
This approach provides a simple way of tuning Q dynamically.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
Improved design and experimental demonstration of ultrahigh-Q C-symmetric H1 hexapole photonic crystal nanocavities
An H1 photonic crystal nanocavity is based on a single point defect and has
eigenmodes with a variety of symmetric features. Thus, it is a promising
building block for photonic tight-binding lattice systems that can be used in
studies on condensed matter, non-Hermitian and topological physics. However,
improving its radiative quality () factor has been considered challenging.
Here, we report the design of a hexapole mode of an H1 nanocavity with a
factor exceeding . We achieved such extremely high- conditions by
designing only four structural modulation parameters thanks to the symmetry of the mode, despite the need of more complicated
optimizations for many other nanocavities. The fabricated silicon photonic
crystal nanocavities exhibited a systematic change in their resonant
wavelengths depending on the spatial shift of the air holes in units of 1 nm.
Out of 26 such samples, we found eight cavities with loaded factors over
one million ( maximum). We examined the difference between the
theoretical and experimental performances by conducting a simulation of systems
with input and output waveguides and with randomly distributed radii of air
holes. Automated optimization using the same design parameters further
increased the theoretical factor by up to , which is two
orders of magnitude higher than in the previous studies. Our work elevates the
performance of the H1 nanocavity to the ultrahigh- level and paves the way
for its large-scale arrays with unconventional functionalities
Photonic-crystal nano-photodetector with ultrasmall capacitance for on-chip light-to-voltage conversion without an amplifier
The power consumption of a conventional photoreceiver is dominated by that of the electric amplifier connected to the photodetector (PD). An ultralow-capacitance PD can overcome this limitation, because it can generate sufficiently large voltage without an amplifier when combined with a high-impedance load. In this work, we demonstrate an ultracompact InGaAs PD based on a photonic crystal waveguide with a length of only 1.7 μm and a capacitance of less than 1 fF. Despite the small size of the device, a high responsivity of 1 A/W and a clear 40 Gbit/s eye diagram are observed, overcoming the conventional trade-off between size and responsivity. A resistor-loaded PD was actually fabricated for light-to-voltage conversion, and a kilo-volt/watt efficiency with a gigahertz bandwidth even without amplifiers was measured with an electro-optic probe. Combined experimental and theoretical results reveal that a bandwidth in excess of 10 GHz can be expected, leading to an ultralow energy consumption of less than 1 fJ/bit for the photoreceiver. Amplifier-less PDs with attractive performance levels are therefore feasible and a step toward a densely integrated photonic network/processor on a chip
Compact 1D-silicon photonic crystal electro-optic modulator operating with ultra-low switching voltage and energy
We demonstrate a small foot print (600 nm wide) 1D silicon photonic crystal electro-optic modulator operating with only a 50 mV swing voltage and 0.1 fJ/bit switching energy at GHz speeds, which are the lowest values ever reported for a silicon electro-optic modulator. A 3 dB extinction ratio is demonstrated with an ultra-low 50 mV swing voltage with a total device energy consumption of 42.8 fJ/bit, which is dominated by the state holding energy. The total energy consumption is reduced to 14.65 fJ/bit for a 300 mV swing voltage while still keeping the switching energy at less than 2 fJ/bit. Under optimum voltage conditions, the device operates with a maximum speed of 3 Gbps with 8 dB extinction ratio, which rises to 11 dB for a 1 Gbps modulation speed
High Transmission in 120-degree Sharp Bends of Inversion-symmetric and Inversion-asymmetric Photonic Crystal Waveguides
Bending loss is one of the serious problems for constructing nanophotonic
integrated circuits. Recently, many works reported that valley photonic
crystals (VPhCs) enable significantly high transmission via 120-degree sharp
bends. However, it is unclear whether the high bend-transmission results
directly from the valley-photonic effects, which are based on the breaking of
inversion symmetry. In this study, we conduct a series of comparative numerical
and experimental investigations of bend-transmission in various triangular PhCs
with and without inversion symmetry and reveal that the high bend-transmission
is solely determined by the domain-wall configuration and independent of the
existence of the inversion symmetry. Preliminary analysis of the polarization
distribution indicates that high bend-transmissions are closely related to the
appearance of local topological polarization singularities near the bending
section. Our work demonstrates that high transmission can be achieved in a much
wider family of PhC waveguides, which may provide novel designs for low-loss
nanophotonic integrated circuits with enhanced flexibility and a new
understanding of the nature of valley-photonicsComment: 15 pages, 7 figures, and 1 table & Supplementary information (18
pages, 15 figures and 1 table). Submitted to Nature Communicatio