Longfei Shen

-1 V bias 67GHz bandwidth Si-contacted germanium waveguide p-i-n photodetector for optical links at 56 Gbps and beyond

We demonstrate a 67 GHz bandwidth silicon-contacted germanium waveguide p-i-n photodetector operating at -1 V with 6.8 fF capacitance. The dark current is below 4 nA. The responsivity is 0.74 A/W at 1550 nm and 0.93 A/W at 1310 nm wavelength. 56 Gbps on-off-keying data reception is demonstrated with clear open eye diagrams in both the C-band and O-band.

Fullerene-assisted electron-beam lithography for pattern improvement and loss reduction in InP membrane waveguide devices

In this Letter, we present a method to prepare a mixed electron-beam resist composed of a positive resist (ZEP520A) and C60 fullerene. The addition of C60 to the ZEP resist changes the material properties under electron beam exposure significantly. An improvement in the thermal resistance of the mixed material has been demonstrated by fabricating multimode interference couplers and coupling regions of microring resonators. The fabrication of distributed Bragg reflector structures has shown improvement in terms of pattern definition accuracy with respect to the same structures fabricated with normal ZEP resist. Straight InP membrane waveguides with different lengths have been fabricated using this mixed resist. A decrease of the propagation loss from 6.6 to 3.3  dB/cm has been demonstrated.

Low-optical-loss, low-resistance Ag/Ge based ohmic contacts to n-type InP for membrane based waveguide devices

We present the development of Ag/Ge based ohmic contacts to n-type InP with both low contact resistances and relatively low optical losses. A specific contact resistance as low as 1.5×10−6 Ω cm2 is achieved by optimizing the Ge layer thickness and annealing conditions. The use of Ge instead of metal as the first deposited layer results in a low optical absorption loss in the telecommunication wavelength range. Compared to Au based contacts, the Ag based metallization also shows considerably reduced spiking effects after annealing. Contacts with different lengths are deposited on top of InP membrane waveguides to characterize the optical loss before and after annealing. A factor of 5 reduction of the propagation loss compared to the conventional Au/Ge/Ni contact is demonstrated. This allows for much more optimized designs for membrane photonic devices.

Optical wireless data transfer enabled by a cascaded acceptance optical receiver fabricated in an InP membrane platform

Utilizing an InP membrane based cascaded acceptance optical receiver (CAO-Rx), we demonstrate 17.4Gbps optical wireless transmission in C-band. By separating light collection and opto-electrical conversion, CAO-Rx provides better optical efficiency and electrical bandwidth simultaneously.

Ohmic Contacts With Ultra-Low Optical Loss on Heavily Doped n-Type InGaAs and InGaAsP for InP-Based Photonic Membranes

In this paper, we present significant reductions of optical losses and contact resistances in AgGe-based ohmic contacts to InP membranes. Due to the high solubility of Si in InGaAs and InGaAsP, heavily doped n-type contact layers are grown on InP wafers. This high doping concentration gives rise to annealing-free ohmic contacts and low contact resistances at the level of 10-7 Ω cm2. It also leads to strong band-filling effects in InGaAs and InGaAsP, which result in low optical absorption losses in the contact layer. Combined with the low optical loss of AgGe, a massive reduction of the propagation loss in membrane waveguides is observed compared with other existing solutions. An additional advantage is the minimal influence of thermal treatments during the processing, leading to very stable high-performing contacts.

Indium Phosphide Integrated Photonics in Membranes

Integrating electronic and photonic functions has become a major issue in the last decade. This integration requires small photonic circuits that are compatible with CMOS processing. Here an approach using an indium phosphide based membrane is reviewed. The high index contrast, leading to micron-sized devices, the full set of photonic functions, including lasers, and the possibility to add these membranes to realized CMOS-circuits, make this an attractive option for hybrid integration. In this paper, the concepts and the required technologies are introduced. A range of realized and proposed membrane devices will be presented, and the prospects of this technique will be discussed.

Membrane-Based Receiver/Transmitter for Reconfigurable Optical Wireless Beam-Steering Systems

In this paper, a novel integrated optical wireless receiver/transmitter is presented. The device is realized on an InP membrane platform where active and passive components are integrated monolithically. It can be reconfigured to either receiver mode or transmitter mode, by simple control on the operation mode of a photodetector (short SOA). Demonstration of the receiver mode in an indoor optical wireless system has shown 17.4-Gbps OFDM signal transmission, illustrating the potential of this concept.

III–V photonic integrated circuits for beyond-telecom applications

In this paper we introduce the III-V photonic integration platforms for emerging applications beyond telecommunications. Recent achievements in the InP generic and InP membrane platforms for wireless and sensing applications are reviewed. The realized chips show the great potential of the InP-based photonic integration due to its full functionality, high flexibility and high performance.

Millimeter Wave Beam Steered Fiber Wireless Systems for 5G Indoor Coverage: Integrated Circuits and SystemsTitle to be Announced

In this talk, we review our recent progress and on-going research on millimeter wave beam steered fiber wireless systems for 5G indoor coverage enabled by the advanced photonic integrated circuit and well-designed fiber-wireless networks.