Recently, researchers at Stanford University have made a breakthrough in the field of laser manufacturing.
They have successfully developed and fabricated a titanium sapphire laser on a chip, an innovation that not only reduces the size of the laser by four orders of magnitude (i.e., to one ten-thousandth of the original size), but also reduces the cost by three orders of magnitude (i.e., to only one-thousandth of the original price).
"This is a disruptive breakthrough in the traditional paradigm," enthuses Prof. Jelena Vuckovic, Professor of Global Leadership and a leading authority on electrical engineering. As the senior author of the article detailing this chip-scale titanium sapphire laser in the journal Nature, she is excited about the future: "Soon, any lab will be able to have hundreds of these high-performance lasers on a single chip, instead of relying on bulky and expensive conventional equipment. It will also be incredibly easy to operate, and it will even be possible to drive it with a green laser pointer."
Joshua Yang, a Ph.D. candidate in the lab, further elaborates on the far-reaching implications of this technology, "These powerful lasers will be able to be used in a wide variety of important applications at a fraction of the cost as we cross over from desktop-class devices to making production-ready products on a chip." He worked on this groundbreaking research with colleagues in Prof. Vuckovic's Nanoscale and Quantum Photonics Laboratory, including research engineer Kasper Van Gasse and postdoctoral scholar Daniil M. Lukin.
Technically, titanium sapphire lasers are favored because they have the largest "gain bandwidth" of any laser crystal. This means that titanium sapphire lasers are able to produce a wider range of wavelengths than other lasers. In addition, their light pulses are emitted extremely quickly, once every trillionth of a second. These excellent performance characteristics will undoubtedly contribute greatly to the widespread application and in-depth development of laser technology in various fields.
In order to build this new type of laser, they first precisely covered a layer of real sapphire crystals with a layer of titanium sapphire on a silicon dioxide platform. The titanium sapphire was then finely ground, etched and polished, and reduced to an ultra-thin layer just a few hundred nanometers thick. Immediately afterward, the team meticulously patterned the waveguide in this ultra-thin layer of material.
This miniaturized design offers significant advantages. From a mathematical standpoint, intensity is the ratio of power to area. Thus, while maintaining the same power as a large-scale laser, the intensity of the laser will be significantly increased due to the reduced area. The researchers noted, "The small size of the laser actually helps us improve efficiency."
Additionally, to further enhance the laser's performance, the research team incorporated a miniature heater. This heater heats the light that passes through the waveguide, allowing Jelena Vuckovic's team the flexibility to adjust the wavelength of the emitted light between 700-1000 nanometers.
This titanium sapphire laser on a microchip shows promising applications in several fields. In quantum physics, it offers an inexpensive and practical solution for downsizing state-of-the-art quantum computers. And in the field of neuroscience, Stanford researchers foresee its direct application in optogenetics, a field that allows scientists to control and influence neuronal activity inside the brain through light, despite the relative bulkiness of the fiber-optic devices currently in common use.
Looking ahead, the team will continue to refine the design of the chip-scale titanium sapphire lasers and explore the possibility of mass-producing them on wafers, thousands of lasers at a time. This summer, Joshua Yang will earn a doctorate based on this research and work to bring this technology to market. We can put thousands of lasers on a 4-inch wafer, and the cost per laser will be close to zero," he says confidently. This will undoubtedly spark a technological revolution."
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