75 GHz germanium waveguide photodetector with 64 Gbps data rates utilizing an inductive-gain-peaking technique

High-performance germanium(Ge)waveguide photodetectors are designed and fabricated utilizing the inductivegain-peaking technique.With the appropriate integrated inductors,the 3-dB bandwidth of photodetectors is significantly improved owing to the inductive-gain-peaking effect without any compromises to the dark current and optical responsivity.Measured 3-dB bandwidth up to 75 GHz is realized and clear open eye diagrams at 64 Gbps are observed.In this work,the relationship between the frequency response and large signal transmission characteristics on the integrated inductors of Ge waveguide photodetectors is investigated,which indicates the high-speed performance of photodetectors using the inductive-gainpeaking technique.

High-speed GeSn resonance cavity enhanced photodetectors for a 50 Gbps Si-based 2 μm band communication system

Expanding the optical communication band is one of the most effective methods of overcoming the nonlinear Shannon capacity limit of single fiber.In this study,GeSn resonance cavity enhanced(RCE)photodetectors(PDs)with an active layer Sn component of 9%–10.8%were designed and fabricated on an SOI substrate.The GeSn RCE PDs present a responsivity of 0.49 A/W at 2μm and a 3-dB bandwidth of approximately 40 GHz at 2μm.Consequently,Si-based 2μm band optical communication with a transmission rate of 50 Gbps was demonstrated by using a GeSn RCE detector.This work demonstrates the considerable potential of the Si-based 2μm band photonics in future high-speed and high-capacity optical communication.

Integrated contra‑directionally coupled chirped Bragg grating waveguide with a linear group delay spectrum

Due to the advantages of low propagation loss,wide operation bandwidth,continuous delay tuning,fast tuning speed,and compact footprints,chirped Bragg grating waveguide has great application potential in wideband phased array beamforming systems.However,the disadvantage of large group delay error hinders their practical applications.The nonlinear group delay spectrum is one of the main factors causing large group delay errors.To solve this problem,waveguides with nonlinear gradient widths are adopted in this study to compensate for the nonlinear efect of the grating apodization on the mode efective index.As a result,a linear group delay spectrum is obtained in the experiment,and the group delay error is halved.

Preparation and Characterization of Porous Carbon from Mixed Leaves for High-Performance Supercapacitors

With the increasing demand of sustainable and eco-friendly resources,it is very attractive to use waste leaves for activated carbon(AC)preparation that can be used in supercapacitors.Considering the practically collected leaves are commonly in mixed nature,and extra efforts are needed to sort these mixtures,we here report the first preparation of AC using mixed leaves from different plants,including Platanus acerifolia(PA),Firmiana platanifolia(FP)and Pistia stratiotes(PS),and compared the results with single leaves-derived AC materials.These leave-derived AC samples were characterized with FESEM,EDS,FTIR and Raman spectroscopy,and electrochemical tests.The AC derived from mixed leaves(PA3FP1PS2AC)showed a good specific capacitance of 246 F·g−1 at 1 A·g−1 in aqueous 3 mol·L^(-1)KOH.This sample further showed the largest specific capacitance of 201 F·g−1 at 5 A·g−1,as compared with the non-mixed AC samples,and a good stability of 100.0%capacitance retention over 1000 cycles.Utilizing mixed leaves for AC preparation is not only demonstrated to be a promising approach of low cost and high-performance AC production for supercapacitor applications,but may also help environmental protection by reducing the invasive species problem.