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ZnO/ZnS/bisindolo quinoxaline-tips (BIQ-TIPs) inorganic/organic nanostructures were fabricated for the application of light/gas dual sensors. Synergic effects of ZnS shell and organic BIQ-TIPs on the ZnO nanorods (NRs) enhanced the photosensing capability owing to efficient charge transfer from BIQ-TIPs to ZnO NRs. Furthermore, ZnS shells covering on the ZnO NRs further extended the photosensing spectrum of ZnO/BIQ-TIPs hybrid structures up to red light. In addition, light-assisted hydrogen gas sensing capability was boosted with the suppositional incorporation of ZnS shell and BIQ-TIPs organic materials. ZnO/ZnS/BIQ-TIPs nanocomposites are promising for light/gas dual sensing application with broadband photosensing wavelength range. [ABSTRACT FROM AUTHOR]

The tunable laser based on distributed feedback (DFB) laser array has a good single-longitudinal-mode property, high wavelength stability, narrow spectrum linewidth, and feasibility for monolithic integration. The tunable in-series DFB laser array (TIDLA) was proposed to avoid the large extra power loss by the optical combiner. But in the TIDLA, a large laser count will cause a large chip length, which brings about low utilization ratio of material, poor mechanical strength, and large power consumption. In this paper, we demonstrated a 4-channel TIDLA with duplex DFB sections. The total chip length was greatly shortened owing the duplexing of DFB sections. A long linearly chirped Bragg grating is implemented in the laser cavity to reduce the grating interference among different lasers. Multiple π phase shifts and two reflector sections are introduced to improve the mode stability. The designed channel spacing is 100 GHz, and the reconstruction-equivalent-chirp technique is used to provide high precision control of the grating phase. Noted that a variation of 0.1 nm in grating period will cause that of 0.65 nm in wavelength. Output power of above 4 mW, SMSR of above 42 dB, and small wavelength deviation of within 0.15 nm was obtained. Besides, fast channel switches of less than 1 μs are obtained by laser on/off switching. The proposed TIDLA might be applied in the NG-PON2 network where the dense wavelength division multiplexing technique and fast channel switching are required. [ABSTRACT FROM AUTHOR]

Multiple-input–multiple-output (MIMO) is a key technology used to meet the requirements of 5G systems. In millimeter-wave (mmWave) bands, directional beamforming is applied at both the transmitter and the receiver to establish an efficient radio link. The mmWave bands specified in 5G specifications range from 24.25 to 40.0 GHz. Accordingly, different countries may allocate different bands to support 5G services because of the availability of the spectrum and the countries’ radio management policies. For international roaming, user equipment (UE) must support multiband operations based on a fixed antenna hardware structure that is designed to target a specific operating band. Hence, the frequency discrepancy that results from using different operating bands causes distortion in the achieved beamforming pattern. In this article, we investigate the impact of frequency discrepancy on beamforming performance in mmWave phased array antenna systems at the UE side, considering the resultant beam pattern and interference. In this effort, we studied three major side effects—deviation of the beamforming direction, change in the effective array length, and change in the normalized interelement spacing. The numerical results indicate that a large frequency discrepancy causes severe distortion in the resultant beamforming pattern and introduces more interference into the system. [ABSTRACT FROM AUTHOR]

Fast optical switches have the potential of lowering the cost, power, and latency of today’s data-center networks. The on-off switching of DFB lasers in arrays is poised to provide extremely fast switching because the on-off time of a DFB laser is the level of sub-nanosecond. However, the key of the DFB laser array based tunable laser lies in the high precision control of the lasing wavelength. In this letter, we proposed and experimentally demonstrated a tunable laser by integrating 16 DFB lasers based on the reconstruction-equivalent-chirp (REC) technique. Without using the conventional e-beam lithography, an equivalent $\lambda $ /4 phase-shift is fabricated in each DFB laser to ensure the single-longitudinal-mode (SLM) yield. Moreover, high precise wavelength spacing is realized. Wavelength deviations of 89.3% DFB lasers are within ±0.2 nm. The output power of all the channels is above 7 mW, and the relative intensity noise is below −130 dB/Hz. By on-off switching the lasers, sixteen channels with 2.4-nm spacing can be fast switched. The switching time between any two channels is less than 50 ns. In addition, a wide-band continuous wavelength tuning range of 38.4 nm can be obtained with a small temperature variation of 18 °C. Owing to the REC technique, the tunable laser via high-density integration of DFB lasers is demonstrated with simple fabrication, high SLM yield, and high wavelength precision, which opens up a path for wide-band and especially fast tunable lasers. [ABSTRACT FROM AUTHOR]

This paper presents a relative pressure sensor fabricated by a standard industrial flexible printed circuit board (FPCB) technology. The passive wireless sensor consists of a variable sensing capacitor and a planar coil inductor. When the external pressure is applied to the sensing capacitor, it changes the air gap and shifts the LC resonance frequency which is detected by an antenna wirelessly. The sensing cavity of the variable capacitor is extended to the opening at the end of an embedded pressure channel in the FPCB strip to enable relative pressure measurement. Measurement results showed that the proposed sensor with such an open sensing cavity had much higher frequency sensitivity (up to 0.4 %/mmHg) compared with the sensor with a sealed cavity (< 0.01 %/mmHg in this work and ≤ 0.08 in literature). With the enhanced sensitivity, the measured pressure resolution could reach 0.2 mmHg. The potential application of the proposed sensor includes gauge pressure measurement with respect to local atmospheric pressure, such as intracranial pressure (ICP) monitoring, without complicated re-calibration procedures. The flat FPCB structure facilitates applications with limited space for sensor installation, such as in the subdural implantation procedures. Furthermore, the proposed technology enables future development of flexible microfluidic devices. [ABSTRACT FROM AUTHOR]

3D hybrid integration based on III-V/Si waveguides by selective undercut wet etching (SUWE) of the lower Si layer has been demonstrated on a silicon-on-insulator (SOI) template. The process was performed on an adhesive-bonding material structure, defined by the upper InP/InAlGaAs (InAlGaAs quantum well) p-i-n heterostructure and the lower 220 nm SOI. After the top p-i-n III-V tapered waveguide was first fabricated and covered by Si3N4, KOH was then used for SUWE of Si layer from SiO2 and Si3N4, forming the bottom SOI single-mode waveguide. In comparison to monolithic III-V waveguide structure (InP based material), the simulated confinement factor of active region shows an enhancement from 10.3% to 16.7%. SOA/EAM devices were also processed and integrated in III-V layer, showing 7.2 dB optical gain at 70 mA injection current in SOA and 21.7 dB extinction ratio within 0~−2 V swing voltage in EAM. The strong quantum confined Stark effect (QCSE) in MQW confirms the improved confinement factor. It suggests a vertical self-alignment scheme could be used for realizing compact and submicron scale heterogeneous integration in a Si photonics template. [ABSTRACT FROM AUTHOR]