S. A. Srinivasan

56 Gb/s Germanium Waveguide Electro-Absorption Modulator

We report a Germanium waveguide electro-absorption modulator with electro-optic bandwidth substantially beyond 50 GHz. The device is implemented in a fully integrated Si photonics platform on 200 mm silicon-on-insulator wafers with 220 nm top Si thickness. Wide open eye diagrams are demonstrated at 1610 nm operation wavelength for nonreturn-to-zero on-off keying (NRZ-OOK) modulation at data rates as high as 56 Gb/s. Dynamic extinction ratios up to 3.3 dB are obtained by applying drive voltages of 2 V peak-to-peak, along with an optical insertion loss below 5.5 dB. The device has a low junction capacitance of just 12.8 fF, resulting in 12.8 fJ/bit of dynamic and ~1.2 mW of static power consumption in typical operating conditions. Wafer-scale performance data are presented and confirm the manufacturability of the device. The demonstrated modulator shows great potential for realizing high-density and low-power silicon photonic transceivers targeting short-reach optical interconnects at serial data rates of 56 Gb/s and beyond.

Active Components for 50 Gb/s NRZ-OOK Optical Interconnects in a Silicon Photonics Platform

We present active components developed in imecs silicon photonics platform that enable 50-Gb/s non-return-to-zero operation using CMOS compatible voltages.

Extraction of carrier lifetime in Ge waveguides using pump probe spectroscopy

Carrier lifetimes in Ge-on-Si waveguides are deduced using time-resolved infrared transmission pump-probe spectroscopy. Dynamics of pump-induced excess carriers generated in waveguides with varying Ge thickness and width is probed using a CW laser. The lifetimes of these excess carriers strongly depend on the thickness and width of the waveguide due to defect assisted surface recombination. Interface recombination velocities of 0.975 × 104 cm/s and 1.45 × 104 cm/s were extracted for the Ge/Si and the Ge/SiO2 interfaces, respectively.

Carrier scattering induced linewidth broadening in in situ P-doped Ge layers on Si

Highly P doped Ge layers are proposed as a material to realize an on-chip laser for optical interconnect applications. In this work, we demonstrate that these donor impurities have a dramatic impact on the excess carrier lifetime and introduce detrimental many-body effects such as linewidth broadening in the gain medium. Linewidth broadening Γopt = 10 meV for undoped Ge and Γopt ≥ 45 meV for Ge with a doping level up to 5.4 × 1019 cm−3 were extracted using photoluminescence spectroscopy and pump-probe spectroscopy. In addition, we observed that the excess carrier lifetime (τc) drops by more than an order of magnitude from 3 ns in undoped Ge to <0.3 ns in doped Ge.Highly P doped Ge layers are proposed as a material to realize an on-chip laser for optical interconnect applications. In this work, we demonstrate that these donor impurities have a dramatic impact on the excess carrier lifetime and introduce detrimental many-body effects such as linewidth broadening in the gain medium. Linewidth broadening Γopt = 10 meV for undoped Ge and Γopt ≥ 45 meV for Ge with a doping level up to 5.4 × 1019 cm−3 were extracted using photoluminescence spectroscopy and pump-probe spectroscopy. In addition, we observed that the excess carrier lifetime (τc) drops by more than an order of magnitude from 3 ns in undoped Ge to <0.3 ns in doped Ge.

Reduction of optical bleaching in phosphorus doped Ge layer on Si

Optical bleaching is studied on undoped and highly doped Ge layer on Si using Transient Absorption Spectroscopy. Upon optical pumping, doped Ge showed a reduction in optical bleaching as compared to undoped Ge due to the homogeneous broadening effect in doped Ge.

Real-time 100 Gb/s NRZ-OOK transmission with a silicon photonics GeSi electro-absorption modulator

We demonstrate single-wavelength, serial and real-time 100 Gb/s NRZ-OOK transmission over 500 m SSMF with a GeSi EAM implemented on a silicon photonics platform. The device was driven with 2 Vpp without 50 Ω termination, allowing a low-complexity solution for 400 GbE short-reach optical interconnects.