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Stochastic computing allows a drastic reduction in hardware complexity using serial processing of bit streams. While the induced high computing latency can be overcome using integrated optics technology, the design of realistic optical stochastic computing architectures calls for energy efficient switching devices. Photonics Crystal (PhC) nanocavities are μm² scale devices offering 100f J switching operation under picoseconds-scale switching speed. Fabrication process allows controlling the Quality factor of each nanocavity resonance, leading to opportunities to implement architectures involving cascaded gates and multi-wavelength signaling. In this paper, we investigate the design of cascaded gates architecture using nanocavities in the context of stochastic computing. We propose a transmission model considering key nanocavity device parameters, such as Quality factors, resonance wavelength, and switching efficiency. The model is calibrated with experimental measurements. We propose the design of XOR gate and multiplexer. We illustrate the use of the gates to design an edge detection filter. System-level exploration of laser power, bit-stream length and bit-error rate is carried out for the processing of gray-scale images. The results show that the proposed architecture leads to 8.5nJ/pixel energy consumption and 512ns/pixel processing time. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate on-chip optical encoder and decoder with ultra-low power consumption. The key device is a silicon photonic crystal (PC) L3 nanocavity with small mode volume. Consequently, the nonlinear effects in the nanocavity are strongly enhanced and could be excited by lower powers. Leveraging different optical power levels, the transmission spectra of the PC nanocavity could be flexibly manipulated. By utilizing proper determining powers, the output powers could be defined as the corresponding optical codes. In the experiment, the binary encoder and decoder are successfully demonstrated with required optical powers of 0.04 mW and 0.032 mW, respectively. Unlike most previous optical encoders and decoders with high powers (tens of milliwatts) or large size (several square millimeters), our scheme which could simultaneously realize the optical encoder and decoder only requires ultra-low powers as 0.04 mW with a compact size of $100~\mu \text{m}^{2}$. To the best of our knowledge, it is a record combined the power consumption and device size for on-chip optical encoder and decoder. [ABSTRACT FROM AUTHOR]

We propose a design of series-connected one-dimensional photonic crystal nanofiber cavity sensor (1-D PC-NCS) and one-dimensional photonic crystal nanofiber bandgap filter (1-D PC-NBF). The proposed structure can get a single air mode for refractive index sensing with its extinction ratio of 58.64 dB. It filters out the high order mode and reduces the interaction between signals. By 3D FDTD, the calculated sensitivity is 848.18 nm/RIU (RIU - refractive index unit). Compared with general silicon on-chip nanobeam cavity, the sensitivity is increased by eight times. The additional 1-D PC-NBF will not change the sensitivity and the position of the resonance wavelength. Therefore, the new design we propose addresses the issue of crosstalk, and can be applied to ultra -high sensitivity index-based gas sensing and biosensing without the need for complicated coupling systems. [ABSTRACT FROM AUTHOR]

On-chip exciting electric modes in individual plasmonic nanostructures are realized widely; nevertheless, the excitation of their magnetic counterparts is seldom reported. Here, we propose a highly efficient on-chip excitation approach of the magnetic dipole mode of an individual split-ring resonator (SRR) by integrating it onto a photonic crystal nanocavity (PCNC). A high excitation efficiency of up to 58% is realized through the resonant coupling between the modes of the SRR and PCNC. A further fine adjustment of the excited magnetic dipole mode is demonstrated by tuning the relative position and twist angle between the SRR and PCNC. Finally, a structure with a photonic crystal waveguide side-coupled with the hybrid SRR–PCNC is illustrated, which could excite the magnetic dipole mode with an in-plane coupling geometry and potentially facilitate the future device application. Our result may open a way for developing chip-integrated photonic devices employing a magnetic field component in the optical field.

An easy to realize L3 photonic crystal nanocavity that exhibits ultrahigh quality factor (Q-factor), ultrasmall mode volume, and a large Q/Vmode is proposed. A resonant cavity mode at 910.625 nm wavelength with Q-factor 4.93 x 105, mode volume 0.802 (λ/n)³, and Q/Vmode6.15 x 105 (λ/n)-3 is reported. The proposed design improves Q-factor by a factor of 84 and Q/Vmode by a factor of 70 in comparison to unoptimized L3 photonic crystal nanocavity. Such a high-quality nanocavity can be used to realize a strongly interacting quantum dot-nanocavity coupled system. [ABSTRACT FROM AUTHOR]

We report on the use of an InP/silicon-on-insulator hybrid photonic crystal nanocavity for the realization of a phase-preserving all-optical power limiter. This function is experimentally demonstrated with 20-Gbit/s nonreturn-to-zero quadrature phase-shift-keying signals. Histogram-based measurements of the phase distributions indicate negligible variations of the phase noise, whereas the amplitude fluctuations are suppressed, confirming the effectiveness of cavity switching for implementing the power-limiter function. Significant power penalty reduction is achieved, indicating a promising application for future photonic circuits. [ABSTRACT FROM PUBLISHER]

Wavelength conversion of a 10-Gb/s (9.35 Gb/s net rate) return-to-zero ON-OFF keying signal is demonstrated using a simple InP photonic crystal H0 nanocavity with Lorentzian line shape. The shifting of the resonance induced by the generation of free-carriers enables the pump intensity modulation to be transferred to a continuous-wave probe with a sufficiently high quality so that the converted signal can be detected with a conventional telecommunication receiver. A clear eye diagram is observed for the converted signal showing a pre-forward error correction bit-error-ratio down to 10-3. [ABSTRACT FROM PUBLISHER]

Abstract: Postgrowth rapid thermal annealing (RTA) was used to modify the optical properties of self-assembled InAs quantum dots (QDs) embedded in a photonic crystal nanocavity. Compared with the reference QDs in the unpatterned regions, it was found that the effect of RTA on the luminescence blueshift of QDs embedded in the nanocavities is similar to that from the unpatterned regions. However, InAs QDs in nanocavities exhibit an anomalous variation of luminescent linewidth during the course of RTA. This could be attributed to the deterioration of InAs QDs at the edge of photonic crystal air holes at high annealing temperatures. The stable position of cavity modes during the RTA temperatures shows the RTA technique could be applied to tune the spectral coupling of QDs/cavities when the QD spectra are on the red side of a cavity mode. [Copyright &y& Elsevier]

Abstract: We investigate light transmission obtained from a three-level V-type emitter embedded in a waveguide-coupled two-mode photonic crystal nanocavity operating in the weak-coupling regime. It is shown that the composite system exhibits double electromagnetically-induced-transparency-like characteristics and a π phase shift while not suffering from absorption in the experimentally available parameter range. The double-frequency transparency of the input light expands the frequency range of EIT and may improve the controllability of EIT. The proposed scheme also provides a way to achieve integrated photonic devices on a chip for applications requiring multiple EIT effect. [Copyright &y& Elsevier]

Abstract: Using three tunnel-coupled quantum dots embedded in waveguide-coupled photonic crystal two-mode nanocavity, we investigate optical transmission-dispersion characteristics of the combined system. It is shown that multiple electromagnetically-induced-transparency (EIT) transmission peaks and strong normal/anomalous dispersion inside the EIT-like windows can be observed in the spectrum. [Copyright &y& Elsevier]

On-chip exciting electric modes in individual plasmonic nanostructures are realized widely; nevertheless, the excitation of their magnetic counterparts is seldom reported. Here, we propose a highly efficient on-chip excitation approach of the magnetic dipole mode of an individual split-ring resonator (SRR) by integrating it onto a photonic crystal nanocavity (PCNC). A high excitation efficiency of up to 58% is realized through the resonant coupling between the modes of the SRR and PCNC. A further fine adjustment of the excited magnetic dipole mode is demonstrated by tuning the relative position and twist angle between the SRR and PCNC. Finally, a structure with a photonic crystal waveguide side-coupled with the hybrid SRR–PCNC is illustrated, which could excite the magnetic dipole mode with an in-plane coupling geometry and potentially facilitate the future device application. Our result may open a way for developing chip-integrated photonic devices employing a magnetic field component in the optical field. [ABSTRACT FROM AUTHOR]

We have introduced a photonic crystal into a single-crystal silicon slab in order to manipulate the light emission. When the lattice constant of a defect-free photonic crystal matches the wavelength of light in the medium, the light emitted from the silicon is resonantly extracted at the photonic band edge within the escape light cone. When the lattice constant is larger than the wavelength, Brillouin zone folding of the photonic band also allows the light to be extracted; we achieved an intensity that was enhanced by a factor of ~ 20 due to the diffraction of internal light into the light cone. We have also created a point defect in photonic crystals with smaller lattice constants that functions as a nanocavity and strongly interacts with the silicon emitter. Four cavity modes were observed, with different Q -factors and emission patterns. The mode orders were assigned using the resonant wavelengths and polarizations. The observed emission at room temperature was enhanced by a factor of ~ 30 in comparison to that of an unprocessed area of silicon-on-insulator. Our study demonstrates that employing a photonic crystal nanocavity in silicon can greatly improve the light extraction efficiency, the characteristics of the radiation pattern, and the internal quantum efficiency. [ABSTRACT FROM PUBLISHER]

Abstract: In this work we propose a new technological approach aimed at improving the performances of DNA-chips in terms of detection sensitivity, signal-to-noise ratio and parallel analyses (spatial and spectral). It is based on the efficient enhancement of markers fluorescence through the insertion of photonic crystal nanocavities (PhC) in DNA-chips, thus giving higher sensitivity and allowing detection of small amounts of target biomolecules in the investigated solution. Moreover, this strategy univocally associates a specific emission wavelength to a specific nanocavity (and to the bio-probe immobilized on it), therefore allowing to infer the presence of a determined element in the solution by a simple spectral analysis of the optical response of the read-out region. This guarantees parallel detection of multiple elements and faster analysis time. The proposed 2D-PhC cavity assisted bio-chip read-out can be easily extended from DNA to a wide range of biomolecules, such as proteins, antibodies, aptamers, receptors. [Copyright &y& Elsevier]

We proposed a nanoscale photonic crystal sensor (NPhCS) on Si slab with triangular lattice. The architecture consists of a resonant cavity coupled with two waveguides on both sides. The nanocavity is formed by introducing a point defect and its resonant peak can shift in response to the changes of refractive index. With COMSOL based on finite element analysis (FEA) technique, the performance parameters of the sensor are analyzed in TM mode. We demonstrate that the light can be gently limited to reduce the loss by adjusting the size of the holes on both sides of the nanocavity. In addition, quality factor (Q) and sensitivity (S) are also been carefully optimized by changing the number of holes on both sides of the nanocavity (N) and the number of infiltrated holes (m) around the nanocavity. Ultimately, an excellent figure of merit (FoM) equal to 357.2 R I U − 1 observed for the optimized structure in this paper is competitive compared with other structures proposed in previous papers. [ABSTRACT FROM AUTHOR]