The laser is a staple of modern technology, finding uses from optical communication and surgery to barcode scanners and laser printers. But most modern lasers still follow a basic blueprint developed more than sixty years ago: a material to convert input energy into light, sandwiched between two finely-tuned mirrors to select and emit a narrow range of light wavelengths.
To make lasers more compact and energy efficient, researchers have in recent years tried to replace these mirrors with sophisticated solutions based on nanotechnology. These novel designs, however, suffer from impractical requirements, such as the need for cryogenic cooling. Now, a group of scientists led by Arseniy Kuznetsov, a Principal Scientist at A*STAR’s Institute of Materials Research and Engineering (IMRE), has combined two optical nanotechnologies to create a room-temperature nanolaser, in collaboration with Hilmi Volkan Demir and the Luminous! Centre of Excellence for Semiconductor Lighting and Displays at Nanyang Technological University, Singapore.
Kuznetsov and his group had previously shown that lasers could be built using ‘nanoantenna arrays,’ periodic arrangements of nano-scale cylinders etched into a material. When the spacing between cylinders is carefully controlled, these arrays emit light at specific wavelengths, allowing them to replace the traditional mirror-based cavity resonators. “These nanoantenna arrays are simpler and cheaper to manufacture than standard solid-state lasers, and may even be integrated into flexible devices,” explained Kuznetsov.
However, Kuznetsov’s first generation of nanolasers only worked at negative 70 degrees Celsius or colder, as the nanoantenna arrays were too inefficient at converting pump energy into light at higher temperatures. This was a problem that Demir could solve with his group’s expertise—growing ‘nanoplatelets’ of cadmium selenide just a few molecules wide. These nanoplatelets convert energy into light very efficiently thanks to quantum effects.
Combining the two technologies by coating the nanoantenna arrays with nanoplatelets resulted in a nanolaser that could lase at room temperature, overcoming the energy conversion inefficiency that had plagued earlier versions. Kuznetsov and his group also showed that the wavelengths of emitted light could still be tuned by changing the spacing of the nanoantenna array in this new, hybrid version.
So far, Kuznetsov’s nanolaser can emit light in short pulses, and his group is currently working on extending this to continuous operation, followed by achieving electrical instead of optical energy input. “If we succeed, this would open up opportunities for multiple potential applications, including flexible displays, sensors, wearables and many more,” Kuznetsov said.
The A*STAR researchers contributing to this work are from the Institute of Materials Research and Engineering (IMRE).