Li-Fi & Lasers: Lighting up Data Transfer Speeds

Fiber-optic cables allow data to travel around the world at the speed of light. But according to SSLEEC collaborator John Bowers, professor in the Department of Electrical and Computer Engineering and director of the UCSB Institute for Energy Efficiency, “As we move from a tethered existence, in which computers are tied to the wall with Ethernet cable, to an untethered, wireless existence, another chapter is emerging in the story of light and data transmission.”

The Industry Connection

One key to the success of the Solid State Lighting and Electric Energy Center (SSLEEC) is its unique operating model. SSLEEC receives no funding from government, foundations, or private individuals; instead, every dollar comes from an ever-evolving, rotating consortium of industry partners. Those partners receive unique benefits in return for their support and provide many to the center as well.

Seeking: Ultra-Efficient Electric Vehicles

Speaking in 2017, Professor Umesh Mishra (Electrical and Computer Engineering) predicted that twenty years from then, twenty percent of all vehicles on the road would be electric. “When the price of solar panels dropped, solar energy took off,” he said. “When the price of batteries in electric vehicles (EVs) drops, they will take off, especially in Brazil, China, and India. EVs and the Internet of Things will be the biggest growth industries in electronics.”

Phosphors: Turning Blue Light White

An LED is the sum of many parts, and one key component for generating all-important white light from an LED is the phosphor. The phosphor — which has nothing to do with the element phosphorus — is a material that is applied over the surface of the blue LED. When the blue light source hits the phosphor, some of it is transformed to appropriate complementary colors that enable the totality of the emission to appear white.

GaN Lasers and Laser-enabled Technologies

In the early 1990s Steven DenBaars began an effort that culminated in 1997, when UCSB became the first university to secure a gallium nitride (GaN)–based laser diode. It was only the fifth such device in the world. The vision was to use it to improve Blu-ray laser technology and then to develop portable laser TV projectors, which, he said in 2017, “We’re still working on twenty years later.”

A Brilliant Challenge: Freeing Light from Semiconductors

It seems straightforward enough: materials are combined according to a precise recipe to make a semiconductor light-emitting diode (LED), a current is run through it, and light is emitted. But it’s not as simple as that, mainly because it is extremely difficult to achieve high levels of efficiency in converting electricity to light in an LED.

LED Lighting: Material Brilliance

In the early 1990s, few people were thinking about semiconductors as a lighting source. Red LEDs were being used as traffic lights and as power-indicator lights on electronic equipment, but lacking blue and green, the path to pervasive LED lighting was hard to see. Infrared was the source of long-wavelength communications used for the internet and for telephone connections, so, accordingly, early semiconductor work was communication-driven.

Theoretically Speaking: The Physics of Semiconductor Science

Breakthrough-yielding laboratory experiments are pursued in parallel with a foundation of theoretical work that informs and guides them. Theory can suggest promising pathways and indicate that others might be dead ends. Professor Chris Van de Walle, who works in computational material science, has spent his thirteen years at UCSB laying the theoretical track to deliver such scientific payloads at the SSLEEC.

Gallium Nitride: The Material that Made the Difference

UCSB College of Engineering professors Steven DenBaars, Umesh Mishra, and James Speck began working with gallium nitride (commonly referred to as GaN) as a semiconductor in 1993, but at the time, funding for such research was largely unavailable because, as DenBaars recalls, “GaN was thought to be useless as a semiconductor.”

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