The Death of Copper: Is Light The Future of Electronics?


Research at Duke University is indicating that copper could be replaced on electronic products. They are studying light as the basis for the next generation information carrier.

Copper has long been what enables information to move from one circuit to another on silicon inside computers. Until now, scientists faced several puzzles when attempting to create and control light on such a small scale.
Dr. Sabarni Palit, Duke University Alumni, speaker on Thin Film Lasers Integrated on Silicon"Getting light onto silicon and controlling it is the first step toward chip scale optical systems," Dr. Sabarni Palit explained. "The challenge has been creating light on such a small scale on silicon, and ensuring that it is received by the next component without losing most of the light," she said.
Palit earned a BE from the University of Pune in India, an MS from Rose Hulman Institute of Technology, Terre Haute Indiana, and just recently her PhD in Optoelectronics from Duke. She gave a talk titled Thin Film Lasers integrated on Silicon at the CMOSET [Communications, Microsystems, Optoelectronics, Sensors, Embedded Technologies] Workshop in Whistler, BC, Canada last Spring. The results of team’s experiments were published online in the journal "Optics Letters: Facet Embedded Thin Film III-V Edge Emitting Lasers Integrated with SU-8 Waveguides on Silicon."
Palit has been working in the laboratory with Nan Marie Jokerst, Executive Director of the Duke University Shared Materials Instrumentation Facility, [SMiF]  an interdisciplinary shared use facility in the Pratt School of Engineering. SMiF provides facilities for Duke researchers and educators and users from other universities, government laboratories, and industry. Similar to other semiconductor fabrication facilities, people can work with intricate materials in a totally "clean" setting.

Using these facilities, the team developed a method of taking the thick substrate off of a laser and bonding this thin film laser to silicon. Microscopic layers of polymer connect the lasers to other structures. The structures on silicon contain tiny light-emitting lasers, and connect these lasers to channels that accurately guide the light to its target, usually another nearby chip or component. The layers of laser and light channels are given specific characteristics, or functions, through nano- and micro-fabrication processes and by removing portions of the substrate with chemicals.
Jokerst says of their current project, "To use light in chip-scale systems is exciting, but the amount of power needed to run these systems has to be very small to make them portable, and they should be inexpensive to produce. There are applications for this in consumer electronics, medical diagnostics and environmental sensing."
The ultra thin lasers were able to create a thin film integrated structure on silicon that contains the light source, and can be kept cool, and accurately guide the wave onto its next connection. Lasers produce heat while producing light, and that heat can degrade the laser. The researchers put a thin band of metals between the laser and silicon substrate to dissipate that heat. Such component integration is essential for the chip-scale, light-based system.