Solomon Assefa

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Integration of optical communication circuits directly into high-performance microprocessor chips can enable extremely powerful computer systems. A germanium photodetector that can be monolithically integrated with silicon transistor technology is viewed as a key element in connecting chip components with infrared optical signals. Such a device should have(More)
We demonstrate optical modulation rates exceeding the conventional cavity linewidth limit using a silicon coupling modulated microring. Small-signal measurements show coupling modulation was free of the parasitic cavity linewidth limitations at rates at least 6× the cavity linewidth. Eye diagram measurements show coupling modulation achieved data rates > 2×(More)
U-report is an open-source SMS platform operated by UNICEF Uganda, designed to give community members a voice on issues that impact them. Data received by the system are either SMS responses to a poll conducted by UNICEF, or unsolicited reports of a problem occurring within the community. There are currently 200,000 U-report participants, and they send up(More)
BACKGROUND The issue of resistance in malarial infection makes development of novel drugs a necessity. An alternative source for discovering such drugs is natural products. Croton macrostachyus H. (Euphorbiaceae) is used in Ethiopian folklore medicine for the treatment of malaria and found to possess antimalarial activity in vitro. However, no further(More)
The Locust infared system provides inexpensive messaging and location information without batteries and without its own network. The system is ‘jwivacy aware” in that it supplies information to the wearable computer user who can then control how much of this information is shared with others or the installed infrastructure. By combining the abilities of(More)
Graphene and other two-dimensional (2D) materials have emerged as promising materials for broadband and ultrafast photodetection and optical modulation. These optoelectronic capabilities can augment complementary metal-oxide-semiconductor (CMOS) devices for high-speed and low-power optical interconnects. Here, we demonstrate an on-chip ultrafast(More)
We present 1-to-8 wavelength (de-)multiplexer devices based on a binary tree of cascaded Mach-Zehnder-like lattice filters, and manufactured using a 90 nm CMOS-integrated silicon photonics technology. We demonstrate that these devices combine a flat pass-band over more than 50% of the channel spacing with low insertion loss of less than 1.6 dB, and have a(More)
This paper describes the design and measured performance of three different silicon photonic switches: a 2 2 switch, a 1 2 switch, and a 4 4 switch. All of the devices have been hybrid integrated with a corresponding custom 90-nm CMOS driver. The 2 2 switch is based on a wavelength-insensitive Mach–Zehnder interferometer (WIMZ) and the 1 2 is based on a(More)