Researchers Shrink Titanium-Sapphire Laser to Chip-Scale

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STANFORD, Calif. July 1, 2024 — Lasers based on titanium-sapphire (Ti:sapphire) provide top performance in fields like quantum optics, spectroscopy, and neuroscience. But that performance comes at a steep cost of not just the multi-thousand dollar price tag, but space and power as well. Ti:sapphire lasers take up several cubic feet and require other high-powered lasers to supply them with enough energy to function. Despite their high level of performance and utility in cutting edge applications, their adoption in the industry has been slow.

Making a jump from tabletop to the microscale, engineers at Stanford University have built a Ti:sapphire laser on a chip. According to the researchers, the prototype is four orders of magnitude smaller (10,000×) and three orders less expensive (1,000×) than any Ti:sapphire laser ever produced.

The researchers’ Ti:sapphire laser is chip-scale four orders of magnitude smaller (10,000x) and three orders less expensive (1,000x) than other Ti:sapphire laser. Here, it is depicted leaning against a block of Ti:sapphire and sitting on a quarter. Courtesy of Yang et al., Nature.
The researchers’ Ti:sapphire laser is four orders of magnitude smaller (10,000x) and three orders less expensive (1,000x) than other Ti:sapphire lasers. Here, the laser is depicted leaning against a block of Ti:sapphire while sitting on a quarter. Courtesy of Yang et al., 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,” said Jelena Vuckovic, Stanford’s Jensen Huang Professor in Global Leadership and senior author of the research.

To fashion the new laser, the researchers began with a bulk layer of Ti:sapphire on a platform of silicon dioxide (SiO2), all riding atop true sapphire crystal. They then grind, etch, and polish the Ti:sapphire to an extremely thin layer just a few hundred nanometers thick. Into that thin layer, they then pattern a swirling vortex of tiny ridges, or a waveguide. These ridges are like fiber-optic cables, guiding the light around and around, building in intensity.

“Mathematically speaking, intensity is power divided by area. So, if you maintain the same power as the large-scale laser, but reduce the area in which it is concentrated, the intensity goes through the roof,” said Joshua Yang, a doctoral candidate in Vuckovic’s lab and co-first author. “The small scale of our laser actually helps us make it more efficient.”

A Ti:sapphire waveguide amplifier created by the researchers that fits in a 0.5mm square. Courtesy of Yang et al., Nature.
A Ti:sapphire waveguide amplifier created by the researchers that fits in a 0.5mm square. Courtesy of Yang et al., Nature.
A microscale heater that warms the light traveling through the waveguides is then added, allowing the team to change the wavelength of the emitted light to tune the color of the light anywhere between 700 nm and 1,000 nm – in the red to infrared range.

“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,” Yang said.

These applications include areas like quantum physics, where the laser could provide an inexpensive and practical solution to scale down state-of-the-art quantum computers. Medical fields could see the Ti:sapphire lasers being used for optogenetics or in compact optical coherence tomography technologies for ophthalmology.

The researchers are currently working on next steps for perfecting their chip-scale Ti:sapphire laser as well as on ways to mass-produce them on wafers and bring them to market.

The research was published in Nature (

Published: July 2024
The term quantum refers to the fundamental unit or discrete amount of a physical quantity involved in interactions at the atomic and subatomic scales. It originates from quantum theory, a branch of physics that emerged in the early 20th century to explain phenomena observed on very small scales, where classical physics fails to provide accurate explanations. In the context of quantum theory, several key concepts are associated with the term quantum: Quantum mechanics: This is the branch of...
Infrared (IR) refers to the region of the electromagnetic spectrum with wavelengths longer than those of visible light, but shorter than those of microwaves. The infrared spectrum spans wavelengths roughly between 700 nanometers (nm) and 1 millimeter (mm). It is divided into three main subcategories: Near-infrared (NIR): Wavelengths from approximately 700 nm to 1.4 micrometers (µm). Near-infrared light is often used in telecommunications, as well as in various imaging and sensing...
A discipline that combines optics and genetics to enable the use of light to stimulate and control cells in living tissue, typically neurons, which have been genetically modified to respond to light. Only the cells that have been modified to include light-sensitive proteins will be under control of the light. The ability to selectively target cells gives researchers precise control. Using light to control the excitation, inhibition and signaling pathways of specific cells or groups of...
Ophthalmology is a branch of medicine that focuses on the anatomy, physiology, and diseases of the eyes and visual system. Ophthalmologists are medical doctors who specialize in the diagnosis, treatment, and prevention of eye disorders and diseases. They are trained to provide comprehensive eye care, including medical, surgical, and optical interventions. Key areas within ophthalmology include: General eye care: Ophthalmologists perform routine eye examinations to assess visual acuity,...
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researchTi:sapphire lasersLasersTi:sapphirespectroscopyquantumquantum computingOpticswaveguidesfiber opticsinfraredoptogeneticsophthalmologytomographyBiophotonicsmedicalAmericasStanford University

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