A team at the University of California San Diego has developed a new type of laser that could lead to smaller and more efficient lasers for medical, computing and optical communication applications. The new laser makes use of an unusual physics phenomenon called bound states in the continuum (BIC), which keeps the light waves confined even when in an open system, and it can be adjusted to emit beams of different wavelengths and shapes.

The BIC phenomenon was originally suggested in 1929, but it wasn't properly studied until the 1970s, and since then it's been observed occurring in wave physics fields like acoustics, microwaves and nanophotonics. The BIC laser created by the UC San Diego team's promises a range of potential benefits.

"Light sources are key components of optical data communications technology in cell phones, computers and astronomy, for example," says Babak Bahari, co-author of the study. "In this work, we present a new kind of light source that is more efficient than what's available today in terms of power consumption and speed."

The BIC laser starts with a semiconductor membrane made with indium, gallium, arsenic and phosphorus, arranged into a grid of tiny cylinders. When the system is hit with a high frequency laser, the membrane emits its own laser beam out the other side, at a lower frequency used for telecommunications.

"Right now, this is a proof of concept demonstration that we can indeed achieve lasing action with BICs," says Boubacar Kanté, lead researcher on the study.

Currently, applications like data communications use vertical-cavity surface-emitting lasers (VCSEL), but the team says its new BIC laser uses can make use of an array of particles just one hundredth of the size of existing devices.

"What's remarkable is that we can get surface lasing to occur with arrays as small as 8 x 8 particles," says Kanté. "The popular VCSEL may one day be replaced by what we're calling the 'BICSEL' — bound state in the continuum surface-emitting laser, which could lead to smaller devices that consume less power."

In addition to its improved efficiency and compactness, BIC lasers can be more versatile thanks to the customizable beams they can emit. With their beams adjusted to certain wavelengths, the new lasers could, for example, find use in medical applications to single out tumors among healthy cells, or by manipulating the beam into shapes like spirals, donuts and bell curves, they can carry up to 10 times more information through optical communication systems.

"Lasers are ubiquitous in the present day world, from simple everyday laser pointers to complex laser interferometers used to detect gravitational waves," says Ashok Kodigala, first author of the study. "Our current research will impact many areas of laser applications."

The researchers say that by scaling up the array, the system could be used to create high-powered lasers for defense and industrial applications, potentially overcoming traditional heat challenges thanks to its improved efficiency. The next step in development is to remove the need to power the BIC laser with another laser, and power it electrically instead.

"An electrically pumped laser is easily portable outside the lab and can run off a conventional battery source," says Kanté.

The research was published in the journal Nature.

Source: UC San Diego

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