Abstract:The majority of the most successful optical modulators in silicon demonstrated in recent years operate via the plasma dispersion effect and are more specifically based upon free carrier depletion in a silicon rib waveguide. In this work we overview the different types of free carrier depletion type optical modulators in silicon. A summary of some recent example devices for each configuration is then presented together with the performance that they have achieved. Finally an insight into some current research trends involving silicon based optical modulators is provided including integration, operation in the mid-infrared wavelength range and application in short and long haul data transmission links.

Flexible integrated circuits with complex functionalities are the missing link for the active development of wearable electronic devices. Here, we report a scalable approach to fabricate self-aligned graphene microwave transistors for the implementation of flexible low-noise amplifiers and frequency mixers, two fundamental building blocks of a wireless communication receiver. A devised AlOx T-gate structure is used to achieve an appreciable increase of device transconductance and a commensurate reduction of the associated parasitic resistance, thus yielding a remarkable extrinsic cutoff frequency of 32 GHz and a maximum oscillation frequency of 20 GHz; in both cases the operation frequency is an order of magnitude higher than previously reported. The two frequencies work at 22 and 13 GHz even when subjected to a strain of 2.5%. The gigahertz microwave integrated circuits demonstrated here pave the way for applications which require high flexibility and radio frequency operations.

A 3.1-10.6 GHz ultra-wideband (UWB) low noise amplifier (LNA) utilizing a current-reused technique and a simple high-pass input matching network is proposed. The implemented LNA presents a maximum power gain of 16 dB, and a good input matching of 50 in the required band. An excellent noise figure (NF) of 3.1-6 dB was obtained in the frequency range of 3.1-10.6 GHz with a power dissipation of 11.9 mW under a 1.8-V power supply. The proposed UWB LNA demonstrates the highest power gain and lowest NF among the published works in 0.18-m CMOS technology.

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