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Researchers at Stanford University have developed a chip-scale titanium-sapphire (Ti:sapphire) laser, significantly reducing the size and cost of this powerful technology. Ti:sapphire lasers are known for their unmatched performance in fields such as quantum optics, spectroscopy, and neuroscience but have traditionally been large, expensive, and energy-intensive.

“This is a complete departure from the old model,” said Jelena Vučković, the Jensen Huang Professor in Global Leadership and senior author of the paper introducing the chip-scale Ti:sapphire laser published in Nature. “Instead of one large and expensive laser, any lab might soon have hundreds of these valuable lasers on a single chip. And you can fuel it all with a green laser pointer.”

The new prototype is 10,000 times smaller and 1,000 times less expensive than traditional Ti:sapphire lasers. Joshua Yang, a doctoral candidate in Vučković’s lab and co-first author of the study along with research engineer Kasper Van Gasse and postdoctoral scholar Daniil M. Lukin, highlighted the profound benefits: “When you leap from tabletop size and make something producible on a chip at such a low cost, it puts these powerful lasers in reach for a lot of different important applications.”

Ti:sapphire lasers are valued for their large gain bandwidth—the range of colors they can produce—and ultrafast light pulses issued every quadrillionth of a second. The new laser fits on a chip measured in square millimeters. If mass-produced on wafers, thousands or even tens-of-thousands could fit on a disc that fits in the palm of a hand.

“A chip is light. It is portable. It is inexpensive and it is efficient,” Yang said. “There are no moving parts. And it can be mass-produced.”

To create the new laser, researchers began with titanium-sapphire layered on silicon dioxide atop sapphire crystal. They then ground, etched, and polished the Ti:sapphire to an extremely thin layer before patterning tiny ridges that guide light around to build intensity.

The remaining piece is a microscale heater that warms light traveling through waveguides to change its wavelength between 700 and 1,000 nanometers—covering red to infrared.

Vučković's team sees potential applications across various fields including quantum physics for scaling down quantum computers; neuroscience for optogenetics; ophthalmology for chirped pulse amplification in laser surgery; and optical coherence tomography technologies.

Next steps involve perfecting their chip-scale Ti:sapphire laser for mass production on wafers.

“We could put thousands of lasers on a single 4-inch wafer,” Yang said. “That’s when the cost per laser starts to become almost zero.”

Contributing authors include postdoctoral scholar Melissa A. Guidry and doctoral candidates Geun Ho Ahn and Alexander D. White. Vučković is also affiliated with Stanford Bio-X, Stanford PULSE Institute, and Wu Tsai Neurosciences Institute.

Funding came from several sources including the Institute of Engineering and Technology A.F. Harvey Prize; Vannevar Bush Faculty Fellowship from the U.S Department of Defense; DARPA; AFOSR; Stanford Nano Shared Facilities/Stanford Nanofabrication Facility supported by NSF.

For further information contact Jill Wu at jillwu@stanford.edu.

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