Avalanche photodiodes on silicon photonics

Silicon photonics technology has drawn significant interest due to its potential for compact and high-performance photonic integrated circuits.The Ge-or III-V material-based avalanche photodiodes integrated on silicon photonics provide ideal high sensitivity optical receivers for telecommunication wavelengths.Herein,the last advances of monolithic and hetero-geneous avalanche photodiodes on silicon are reviewed,including different device structures and semiconductor systems.

An advanced Ⅲ-Ⅴ-on-silicon photonic integration platform

In many application scenarios,silicon(Si)photonics favors the integration of Ⅲ-Ⅴ gain material onto Si substrate to real-ize the on-chip light source.In addition to the current popular integration approaches of Ⅲ-Ⅴ-on-Si wafer bonding or dir-ect heteroepitaxial growth,a newly emerged promising solution of epitaxial regrowth on bonded substrate has attracted a lot of interests.High-quality Ⅲ-Ⅴ material realization and successful laser demonstrations show its great potential to be a promising integration platform for low-cost,high-integration density and highly scalable active-passive photonic integra-tion on Si.This paper reviews recent research work on this regrowth on bonded template platform including template de-velopments,regrown material characterizations and laser demonstrations.The potential advantages,opportunities and challenges of this approach are discussed.

Mechanisms of enhanced sub-bandgap absorption in high-speed all-silicon avalanche photodiodes

All-silicon (Si) photodiodes have drawn significant interest due to their single and simple material system and perfect compatibility with complementary metal-oxide semiconductor photonics. With the help from a cavity enhancement effect, many of these photodiodes have shown considerably high responsivity at telecommunication wavelengths such as 1310 nm, yet the mechanisms for such high responsivity remain unexplained. In this work,an all-Si microring is studied systematically as a photodiode to unfold the various absorption mechanisms.At-6.4 V, the microring exhibits responsivity up to0.53 A∕W with avalanche gain, a 3 dB bandwidth of25.5 GHz, and open-eye diagrams up to 100 Gb/s. The measured results reveal the hybrid absorption mechanisms inside the device. A comprehensive model is reported to describe its working principle, which can guide future designs and make the all-Si microring photodiode a promising building block in Si photonics.

Ⅲ/Ⅴ-on-Si MQW lasers by using a novel photonic integration method of regrowth on a bonding template

Silicon photonics is becoming a mainstream data-transmission solution for next-generation data centers,highperformance computers,and many emerging applications.The inefficiency of light emission in silicon still requires the integration of a Ⅲ/Ⅴ laser chip or optical gain materials onto a silicon substrate.A number of integration approaches,including flip-chip bonding,molecule or polymer wafer bonding,and monolithic Ⅲ/Ⅴ epitaxy,have been extensively explored in the past decade.Here,we demonstrate a novel photonic integration method of epitaxial regrowth of Ⅲ/Ⅴ on a Ⅲ/Ⅴ-on-SOI bonding template to realize heterogeneous lasers on silicon.This method decouples the correlated root causes,i.e.,lattice,thermal,and domain mismatches,which are all responsible for a large number of detrimental dislocations in the heteroepitaxy process.The grown multi-quantum well vertical p-i-n diode laser structure shows a significantly low dislocation density of 9.5×104 cm^(−2),two orders of magnitude lower than the state-of-the-art conventional monolithic growth on Si.This low dislocation density would eliminate defect-induced laser lifetime concerns for practical applications.The fabricated lasers show room-temperature pulsed and continuous-wave lasing at 1.31μm,with a minimal threshold current density of 813 A/cm^(2).This generic concept can be applied to other material systems to provide higher integration density,more functionalities and lower total cost for photonics as well as microelectronics,MEMS,and many other applications.

Inductive transfer learning for unlabeled target-domain via hybrid regularization

Recent years have witnessed an increasing interest in transfer learning. This paper deals with the classification problem that the target-domain with a different distribution from the source-domain is totally unlabeled, and aims to build an inductive model for unseen data. Firstly, we analyze the problem of class ratio drift in the previous work of transductive transfer learning, and propose to use a normalization method to move towards the desired class ratio. Furthermore, we develop a hybrid regularization framework for inductive transfer learning. It considers three factors, including the distribution geometry of the target-domain by manifold regularization, the entropy value of prediction probability by entropy regularization, and the class prior by expectation regularization. This framework is used to adapt the inductive model learnt from the source-domain to the target-domain. Finally, the experiments on the real-world text data show the effectiveness of our inductive method of transfer learning. Meanwhile, it can handle unseen test points.

Phosphine oxide-functionalized polyfluorene derivatives:Synthesis,photophysics,electrochemical properties,and electroluminescence performance

A series of phosphine oxide-functionalized polyfluorene derivatives,PFH-PO-40-1 (P1),PFH-PO-20-1 (P2),PFH-PO-10-1 (P3),and PFH-PO-1-1 (P4),were prepared via a palladium-mediated Suzuki cross-coupling reaction.The structures and purities of all polymers were fully characterized by 1H and 13C NMR,UV-vis and photoluminescent spectroscopy,gel permeation chromatography,and TGA/DSC.Their emission features showed single broad peaks at about 445 nm in film,compared with those in dilute solutions,which might be caused by some degree of aggregation in the excited states of the backbones.The best electroluminescence (EL) performance of these polymers with configuration of ITO/PEDOT:PSS/Polymer/Alq3/LiF/Al was obtained from P1 (current efficiency was 4.2 Cd/A at 6V).

Silicon-plus photonics

Silicon photonics has become very popular because of their compatibility with mature CMOS technologies. However, pure silicon is still very difficult to be utilized to obtain various photonic functional devices for large-scale photonic integration due to intrinsic properties. Silicon-plus photonics, which pluses other materials to break the limitation of silicon, is playing a very important role currently and in the future. In this paper, we give a review and discussion on the progresses of siliconplus photonics, including the structures, devices and applications.

Reflections on the security proofs of Boneh-Franklin identity-based encryption scheme

In this paper, we first review the existing proofs of the Boneh-Franklin identity-based encryption scheme (BF-IBE for short), and show how to admit a new proof by slightly modifying the specifications of the hash functions of the original BF-IBE. Compared with prior proofs, our new proof provides a tighter security reduction and minimizes the use of random oracles, thus indicates BF-IBE has better provable security with our new choices of hash functions. The techniques developed in our proof can also be applied to improving security analysis of some other IBE schemes. As an independent technical contribution, we also give a rigorous proof of the Fujisaki-Okamoto (FO) transformation in the case of CPA-to-CCA, which demonstrates the efficiency of the FO-transformation (CPA-to-CCA), in terms of the tightness of security reduction, has long been underestimated. This result can remarkably benefit the security proofs of encryption schemes using the FO-transformation for CPA-to-CCA enhancement.

Recent Progress in Heterogeneous Ⅲ-Ⅴ-on-Silicon Photonic Integration

Silicon(Si)photonics is a disruptive technology on the fast track to revolutionise integrated photonics.An indispensable branch thereof,heterogeneous Si integration,has also evolved from a science project 15 years ago to a growing business and compelling research field today.We focus on the scope of Ⅲ-Ⅴ compound semiconductors heterogeneously integrated on Si substrates.The commercial success of massively produced integrated optical transceivers based on first-generation innovation is discussed.Then,we review a number of technological breakthroughs at the component and platform levels.In addition to the numerous new device performance records,our emphasis is on the rationale behind and the design principles underlying specific examples of materials and device integration.Finally,we offer perspectives on development trends catering to the increasing demand in many existing and emerging applications.

Next-generation siliconphotonics:introduction

In the past decade,silicon photonics has been making tremendous progress in terms of device functionality and performances as well as circuit integration for many practical applications ranging from communication,sensing,and information processing.This special issue,including four review articles and nine research articles,aims to provide a comprehensive overview of this exciting field.They offer a collective summary of recent progresses,in-depth discussions of the state-of-the-art,and insights into forthcoming developments that are well poised to drive silicon photonics technology into its next generation.

Ultra-power-efficient heterogeneous Ⅲ–Ⅴ/Si MOSCAP(de-)interleavers for DWDM optical links

We discuss the design and demonstration of various Ⅲ–Ⅴ/Si asymmetric Mach–Zehnder interferometer(AMZI)and ring-assisted AMZI(de-)interleavers operating at O-band wavelengths with 65 GHz channel spacing. The wafer-bonded Ⅲ–Ⅴ/Si metal-oxide-semiconductor capacitor(MOSCAP) structure facilitates ultra-low-power phase tuning on a heterogeneous platform that allows for complete monolithic transceiver photonic integration.The second-and third-order MOSCAP AMZI(de-)interleavers exhibit cross-talk(XT) levels down to -22 dB and -32 dB with tuning powers of 83.0 nW and 53.0 nW, respectively. The one-, two-, and three-ring-assisted MOSCAP AMZI(de-)interleavers have XT levels down to -27 dB,-22 dB, and-20 dB for tuning powers of 10.0 nW, 7220.0 nW, and 33.6 nW, respectively. The leakage current density is measured to be in the range of 1.6–27 μA∕cm^(2). To the best of our knowledge, we have demonstrated for the first time, athermal Ⅲ–Ⅴ/Si MOSCAP(de-)interleavers with the lowest XT and reconfiguration power consumption on a silicon platform.