We present a widely tunable 25 Gbps transmitter that integrates a V-Cavity Laser and an electro-absorption modulator using an identical epitaxial layer scheme. The transmitter exhibits a wavelength ...tuning of 41 channels with 100 GHz spacing and a side-mode suppression ratio above 42 dB by varying the TEC temperature by 32 °C. All channels show clear eye diagram openings at a rate of 25 Gbps with a dynamic extinction ratio higher than 9 dB at a fixed peak-to-peak driving voltage of 2 V. Bit-error-rate measurements demonstrate a power penalty less than 3 dB for transmission through 10 km of standard single-mode fiber. This tunable transmitter offers a cost-effective solution that is suitable for use in DWDM access networks.
Lysine glutarylation is new type of protein acylation modification in both prokaryotes and eukaryotes. To better understand the molecular mechanism of glutarylation, it is important to identify ...glutarylated substrates and their corresponding glutarylation sites accurately. In this study, a novel bioinformatics tool named GlutPred is developed to predict glutarylation sites by using multiple feature extraction and maximum relevance minimum redundancy feature selection. On the one hand, amino acid factors, binary encoding, and the composition of k-spaced amino acid pairs features are incorporated to encode glutarylation sites. And the maximum relevance minimum redundancy method and the incremental feature selection algorithm are adopted to remove the redundant features. On the other hand, a biased support vector machine algorithm is used to handle the imbalanced problem in glutarylation sites training dataset. As illustrated by 10-fold cross-validation, the performance of GlutPred achieves a satisfactory performance with a Sensitivity of 64.80%, a Specificity of 76.60%, an Accuracy of 74.90% and a Matthew's correlation coefficient of 0.3194. Feature analysis shows that some k-spaced amino acid pair features play the most important roles in the prediction of glutarylation sites. The conclusions derived from this study might provide some clues for understanding the molecular mechanisms of glutarylation.
Fluorinated aromatic polyimide (FAPI) films with rigid polymer backbones have been prepared by chemical imidization approach. The polyimide films exhibited excellent mechanical properties including ...elastic modulus of up to 8.4 GPa and tensile strength of up to 326.7 MPa, and outstanding thermal stability including glass transition temperature (
) of 346.3-351.6 °C and thermal decomposition temperature in air (
) of 544.1-612.3 °C, as well as high colorless transmittance of >81.2% at 500 nm. Moreover, the polyimide films showed stable dielectric constant and low dielectric loss at 10-60 GHz, attributed to the close packing of rigid polymer backbones that limited the deflection of the dipole in the electric field. Molecular dynamics simulation was also established to describe the relationship of molecular structure and dielectric loss.
Two Edge-input arrayed waveguide gratings (AWGs) with star couplers of Confocal and Rowland configurations, respectively, are experimentally investigated and the one with the Rowland configuration ...shows better performance in terms of insertion loss and crosstalk. Based on the optimized Rowland configuration, two 64 × 0.4 nm ultra-compact on-chip spectrometers using bidirectional AWGs with two side inputs and different lengths of free propagation region (FPR) are designed and fabricated. Due to the utilization of two side inputs, the footprint of AWG spectrometer is significantly reduced compared to the conventional one center-input AWG spectrometer with the same resolution. The reduced footprint contributes to the performance improvement for an AWG spectrometer on high index contrast platforms, which is verified in our fabricated spectrometers on the silicon-on-insulator platform. The demonstrated ultra-compact on-chip spectrometer has large potential applications in miniaturized spectral analysis systems on a chip.
We introduced a label-free sensing system based on an array of microring resonators (MRRs) which was successfully employed for human serum albumin (HSA) detection. The sensing-ring surface was ...functionalized to immobilize anti-HSA, facilitating HSA binding. Our refractive index sensing system demonstrates high sensitivity at 168 nm/RIU and a low limit of detection (LOD) of 63.54 ng/mL, closely comparable to current HSA detection methods. These findings confirm the potential of MRRs as biocompatible sensors for HSA detection. This system holds great promise as an innovative platform for the detection of HSA, carrying significant importance in medical diagnostics.
Ultra-compact on-chip spectrometers with high resolution and large bandwidth play a crucial role in miniaturized spectroscopic analysis systems. Here we present a novel polarization-insensitive ...micro-spectrometer with high resolution and large bandwidth based on a ( N + 3) × ( N + 3) arrayed waveguide grating (AWG) on silicon-on-insulator (SOI) platform. The proposed AWG can be viewed as two same 3 × N AWGs with each one having three input waveguides with channel spacing of 4/3 Δ λ and N output waveguides with channel spacing of Δ λ . The three input waveguides are time division multiplexed, i.e., they are excited one by one in sequence. As a result, combining all spectral responses of each input, a micro-spectrometer with channel wavelength spacing enhanced to one-third Δ λ and channel number enlarged to 3 × ( N - 2) is achieved, only using N output channels. The polarization diversity scheme is utilized to address the polarization sensitive issue of silicon nano-waveguide, i.e., the AWG operates at a counter-propagating manner to process each polarization, respectively. In experiment, we demonstrate a micro-spectrometer with 81 channels and channel wavelength spacing of 0.4 nm by employing a 32 × 32 AWG on the SOI platform. The footprint of the fabricated micro-spectrometer is only 1.1 × 2.35 mm 2 . Experimental results show that the spectrometer has on-chip losses ranging from -5.8 to -2.5 dB, noise level of better than 17 dB, polarization dependent wavelength shift (PD λ ) of less than 0.07 nm and polarization dependent loss (PDL) of less than 1.5 dB, for all 81 wavelength channels. The resolution of the micro-spectrometer is mainly dependent on the 3-dB bandwidth of each channel and is simulated to be ∼0.65 nm. The proposed ultracompact and polarization insensitive high-resolution on-chip spectrometer provides a very promising approach for achieving miniaturized spectrometer-on-a-chip with good performance for applications such as in fiber Bragg grating (FBG) sensor readout unit and optical waveguide sensor systems.
We report the use of highly ordered, dense, and regular arrays of in-plane silicon nanowires as building blocks to produce highly sensitive and well-reproducible surface-enhanced Raman scattering ...(SERS). A combination of Au nanospheres (AuNPs) and Au coated silicon nanowires (AuSiNWs) was found to exhibit one order higher enhancement of SERS signal compared with that of the normal AuSiNWs substrate. The experimental results were further evidenced by simulating the electrical field distributions using 3-D finite-difference time-domain (3-D-FDTD). The prominence and potential applications of biosensors using AuNPs/AuSiNWs arrays were demonstrated by the improved sensitivity in detecting SERS signal of 4, 4'-Bipyridine.
We demonstrate a monolithic InP-based photonic integrated circuit (PIC) consisting of four tunable V-cavity lasers (VCLs), a cyclic echelle diffraction grating router (EDGR) and four semiconductor ...optical amplifiers (SOAs). Quantum-well intermixing (QWI) technique is used to produce three different bandgap energies on the chip. Single VCL with 30 nm tuning range at <inline-formula> <tex-math notation="LaTeX">1.3~\mu \text{m} </tex-math></inline-formula> wavelength band and up to 40 dB side-mode-suppression ratio (SMSR) is experimentally demonstrated. The chip has a 4.5 nm channel spacing and 18 nm free-spectral range (FSR). Measured spectrum of all the 16 input-output combinations show cyclic response.
We report a widely tunable monolithically integrated V-coupled cavity interband cascade laser (ICL) emitting near 3.4 μm. The mode selection is achieved using a half-wave V-coupler designed for the ...ICL in the mid-infrared range without any grating. The side-mode suppression ratio is demonstrated up to 35.7 dB. In the heat-sink temperature range from 130 K to 140 K, single-mode wavelength tuning range of over 100 nm from 3329.9 nm to 3431.3 nm has been attained by adjusting both current and temperature. These results show that the V-coupled cavity ICLs are very promising for multi-species trace gas absorption spectroscopy with a high sensitivity.
We theoretically analyze and experimentally demonstrate improved half-wave couplers for widely tunable V-cavity lasers. An overlapping-image 6×6 MMI coupler and an aggregating-image 16×16 MMI coupler ...are investigated, which give optimal coupling phase and coefficient for achieving high single-mode selectivity in V-cavity lasers while producing a low loss. A single-electrode controlled tuning of 38 channels is achieved with channel spacings of 100GHz and 150GHz. By combining two single-electrode tuning segments at different temperatures, a wavelength tuning range of 52 channels from 1515nm to 1585nm is obtained, and the side mode suppression ratios (SMSRs) reach 45 dB.
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