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We proposed and experimentally demonstrated a simple and novel photonic spiking neuron based on a distributed feedback (DFB) laser subject to side-mode optical pulse injection (SMOPI). The DFB laser chip is designed and fabricated based on asymmetric equivalent π phase shift (π-EPS) with the reconstruction-equivalent-chirp (REC) technique. Under side-mode continuous-wave (CW) optical injection, excitability pulse was experimentally observed during the dominant mode switching process due to the injection-locked effect. Based on the transition between the excitability regime and the side-mode injection locking effect, the controllable and repeatable neuron-like spiking response can be realized when external stimulus pulses are electro-optically modulated on the CW optical carrier. The experimental results show that the spike threshold, temporal integration, and refractory period, which are important spike processing mechanisms in biological neurons, can all be achieved in the optically-injected DFB laser. The experimental findings are also verified numerically with a rate equation model that considers the SMOPI. To the best of our knowledge, this is the first experimental demonstration of a photonic spiking neuron based on a DFB laser sub ject to SMOPI, which holds promise for realizing large-scale photonic spiking neuron arrays for hardware photonic spiking neural network chips. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the regulatory function of lncRNA RMRP in non-alcoholic fatty liver disease (NAFLD). In vitro and in vivo NAFLD models were constructed. Hematoxylin & Eosin (H&E) and Oil-Red O staining assays were conducted to observe the morphology and lipid accumulation in liver tissues. Triglycine (TG) secretion was detected by ELISA assay. The expression levels of RMRP, microRNA-206, PTPN1 (protein tyrosine phosphatase, non-receptor type 1), and their downstream genes were assessed by qRT-PCR and Western blot. The regulatory relationship among these molecules was determined by luciferase reporter and RNA pull-down assays. RMRP and PTPN1 were up-regulated, while miR-206 was down-regulated in the liver tissues of NAFLD patients and rat model. RMRP inhibition improved the pathological state and liver function-related indexes of liver lipid deposition in the liver tissues of NAFLD rats. RMRP inhibition alleviated steatosis and TG secretion in free fatty acids (FFA)-treated AML-12 cells. RMRP could bind to miR-206 and downregulate its expression. Meanwhile, RMRP inhibition attenuated lipid accumulation by downregulating the PTPN1-PP2ASP1-SREBP1C pathway. Furthermore, RMRP inhibited the miR-206/PTPN1-SREBP1C signaling pathway in NAFLD rats and FFA-treated AML-12 cells. RMRP inhibition prevented NAFLD progression in rats via targeting the miR-206/PTPN1 axis. [ABSTRACT FROM AUTHOR]

A new effect of transient mode competition in directly modulated DFB laser based on equivalent phase-shift (EPS) technique is presented and studied. Since there are multi-order reflections in EPS structure and if the 0th order subgrating is properly designed, the transient lasing of 0th order will occur during the rising time of the injection current. As a result, transient mode competition between -1st order (main mode) and 0th order will occur accordingly. This can consume redundant carrier and suppress the transient relaxation oscillation, which may be applied in some areas like on-off switching modulation of DFB semiconductor lasers. As an example, an equivalent π phase shift (π-EPS) is carefully designed to realize the effect. In such a laser the 0th order wavelength is in the margin of the material gain region and the -1st order wavelength is around the gain peak, while the stable single longitudinal mode (SLM) operation of the -1st order is guaranteed. The simulation investigation is performed. Good results with suppressed relaxation oscillation and 1.25 Gb/s directly on-off modulation (32 dB extinction ratio) are demonstrated. We believe it provides a new kind of method for on-off switching with high extinction ratio and weak relaxation oscillation. [ABSTRACT FROM AUTHOR]

In this article, we report the first experimental demonstration of the three-phase-shifted (3PS) DFB semiconductor laser with buried heterostructure based on the Reconstruction-Equivalent-Chirp (REC) technique. The simulation results show that the performances of the equivalent 3PS DFB semiconductor laser are nearly the same as those of the true 3PS laser. Compared with the quarter-wave-phase shift (QWS) DFB semiconductor laser, the 3PS DFB semiconductor laser shows better single-longitude-mode (SLM) property even at high injection current with high temperature. However, it only changes the μm-level sampling structures but the seed grating is uniform using the REC technique. Therefore, its fabrication cost is low. [ABSTRACT FROM AUTHOR]

In this article, we report the first experimental demonstration of an eight-wavelength λ/8 phased-shifted laser array based on the REC technique in the 1.3 μm wavelength domain. Measurement results exhibit good linearity of lasing wavelength with +/−0.35 nm wavelength residual. The SLM property was ensured with SMSRs all larger than 38 dB. Moreover, the direct-modulation performance was also tested. The experimental results show that the modulation bandwidth can reach up to 13 GHz even at the small injection current of 40 mA and the measured spurious-free dynamic range (SFDR) is up to 87 dB/Hz, which shows good linearity. These measurements show that REC-based λ/8 phased-shifted laser array has good modulation performance and it may find potential application in actual fiber-optic systems. [ABSTRACT FROM AUTHOR]

A compact multi-wavelength hybrid-integrated directly-modulated distributed-feedback laser (DML) transmitter optical sub-assembly (TOSA) has been achieved in our laboratory. The 8-channel distributed feedback (DFB) lasers are monolithically integrated based on the reconstruction-equivalent-chirp (REC) technology. With the high-density and high-speed packaging technique, the laser array and a multi-mode interference (MMI) multiplexer are assembled in the TOSA. The channel spacing of the TOSA is 200 GHz between adjacent lasers. It meets the 8 × 12.5 Gb/s operation demand and gives rather low channel crosstalk of less than −25 dB. This compact TOSA is of effective cost and shows good stability for mass production, which is expected to improve the performance of devices in access networks, data centers and supercomputing. [ABSTRACT FROM AUTHOR]

A 1.3 μm distributed feedback (DFB) semiconductor laser with equivalent λ/4 phase shift based on reconstruction equivalent chirp (REC) technique is numerically studied and experimentally demonstrated. The simulation results show that the 1.3 μm DFB laser with equivalent λ/4 phase shift based on the REC technique performs the same as that of actual λ/4 phase shift DFB laser, with nearly the same P-I curves, the internal power distributions and the output ASE spectra. Compared with the traditional λ/4 phase shift DFB laser, the REC based laser only changes the sampling structures with the uniform seed waveguide grating instead of the actual grating structures. As a result, the fabrication of such laser will be very easy. In this paper, we successfully fabricated the 1.3 μm DFB laser based on the REC technique for the first time to the best of our knowledge. [ABSTRACT FROM AUTHOR]

Mixed-level designs are widely used in the practical experiments. When the levels of some factors are difficult to be changed or controlled, fractional factorial split-plot (FFSP) designs are often used. This paper investigates the sufficient and necessary conditions for a $${2^{(n_{1}+n_{2})-(k_1+k_2)}4_s^{1}}$$ FFSP design with resolution III or IV to have various clear factorial effects, including two types of main effects and three types of two-factor interaction components. The structures of such designs are shown and illustrated with examples. [ABSTRACT FROM AUTHOR]

We summarized the design, fabrication challenges and important technologies for multi-wavelength laser transmitting photonic integration. Technologies discussed include multi-wavelength laser arrays, monolithic integration and modularizing coupling and packaging. Fabrication technique requirements have significantly declined with the rise of reconstruction-equivalent-chirp and second nanoimprint mask technologies. The monolithic integration problem between active and passive waveguides can be overcome with Butt-joint and InP array waveguide grating technologies. The dynamic characteristics of multi-factors will be simultaneously measured with multi-port analyzing modules. The performance of photonic integration chips is significantly improved with the autoecious factors compensation packaging technique. [ABSTRACT FROM AUTHOR]

A distributed feedback (DFB) semiconductor laser with three phase shifts based on reconstruction equivalent chirp (REC) technology is proposed and investigated numerically. With the combination of multiple phase shifts and corrugation pitch modulated (CPM) structure, we also propose a novel and more complex structure named dual CPM, which has a flatter light power distribution along the laser cavity compared with the true double phase shifts DFB laser diode (LD), while the P-I curves are nearly the same. The proposed dual CPM structure is also designed and analyzed based on REC technology. The simulation results show that, the DFB semiconductor laser with complex structure such as phase shifts, or even arbitrary variation of the grating period can be achieved equivalently and easily by changing the sampling structure. But its external characteristics are almost the same as those DFB lasers with true phase shifts, or true arbitrary variation of the grating period. The key advantage of the REC technology is that it varies only the sampling structure and keeps the seed grating (actual grating in sampling structure) period constant. So its fabrication needs only low-cost and standard holographic exposure technology. Therefore we believe this method can achieve the high-end and low-cost DFB LD for mass production. [ABSTRACT FROM AUTHOR]