Alyssa B. Apsel

I am currently a Ph.D. candidate  in Electrical Engineering working on Opto-electronic VLSI for parallel inter-chip communication.  My research advisor is Andreas Andreou in the Sensory Communication and Microsystems Laboratory at Johns Hopkins University.

Research Interest - Opto-electronic VLSI

Internal data rates of processors fabricated in deep submicron CMOS technology have exceeded gigahertz rates. While processing proceeds at GHz internally, off chip wires have held inter-chip clock rates at hundreds of MHz. The rate of inter-chip communication is now the limiting factor in high performance systems. As a result, the Semiconductor Research Corporation has cited interconnect design and planning as a primary research thrust.

Optical inter and intra-chip communication has the potential to solve interconnect problems. Inter-chip opto-electronic communication in three dimensions is complicated by the difficulty of implementing optical vias through substrates. Furthermore, the design of high performance amplifiers for channel interfaces is limited by parasitic effects in today's bulk CMOS processes.

In my research, I attempt to solve inter-chip communication problems through the novel use of optically transparent state-of-the-art silicon on sapphire (SOS) CMOS. Exploiting sapphire substrates that are both optically transparent and insulating, we solve the problem of constructing optical vias and we design high performance receiving circuitry without bulk parasitics.

In addition to practical hardware issues of chip integration, I also examine algorithmic issues of channel coding using unique spatial aspects of 3-D interconnection to transmit digital and analog data.

  Photo of an SOS driver array

Selected Publications

A. Apsel and A. Andreou. An analysis of data reconstruction efficiency using stochastic encoding and an integrating receiver. IEEE Transactions on Circuits and Systems II, Vol. 48, Issue 10, Oct. 2001.

A. Apsel and A. Andreou.  A 5mW, gigabit/s silicon on sapphire CMOS optical receiver.  Electronics Letters, Sept. 12, 2001.

A. Apsel and A. Andreou. Quality of data reconstruction using stochastic encoding and an integrating receiver. MWSCAS, 2000.

A. Apsel, Z. Kalayjian, A. Andreou and Orientation enchancement using opto-electronic VLSI and asynchronous pulse coding. ISCAS, 2000.

R. A. Athale, Z. Kalayjian, A. Apsel, and Hybrid OE-Interconnect VCSEL-CMOS modules based on ultra-thin silicon on sapphire. OSA Annual Meeting 2000.

For more details, look at Alyssa Apsel's Curriculum Vitae.

Click here for my favorite VCSEL tutorial.