Nanolasers Graphic
A schematic of the upconverting nanoparticle (UCNP) coating on top of Ag nanopillar arrays. (Image courtesy of Berkeley Lab)

A research team has used the Molecular Foundry, a Department of Energy Office of Science user facility, to create miniature lasers. These lasers are stable and work continuously. What makes these new lasers unique is that while many previous miniature lasers required very cold temperatures, these work at room temperature. To design them, researchers combined arrays of nanopillars with nanoparticles developed at the Foundry that can absorb two photons of light and emit them as a single photon with higher energy.

Miniaturized lasers are increasingly important for generating coherent beams of light. Several technologies need this type of light, including light-based quantum technologies, machines that take images of cells inside of living organisms, solid-state lighting, and fast 3D sensors in smartphones. These technologies need lasers that can work continuously at room temperature.

Previous nanolasers were not efficient and too unstable. These nanolasers require less energy to function compared to lasers that use similar technologies. They are also stable and provide continuous waves of light at room temperature. These robust, low-power lasers will be useful in a range of fields including medicine and quantum information science.

Miniaturized lasers are an emerging platform for generating coherent light for quantum photonics, in vivo cellular imaging, solid-state lighting, and fast 3D sensing in smartphones. Continuous-wave (CW) lasing at room temperature is critical for integration with opto-electronic devices and enhanced modulation of optical interactions. A critical limitation has been that, until now, nanoscale lasers have been limited to pulsed pump sources or low temperature operation. Previous nanolasers were much less efficient than macroscale lasers and generated excess heat, which destabilized them.

A research team has developed upconverting nanolasers by combining upconverting nanoparticles with nanopillar arrays to produce stable and continuous plasmon lasing at room temperature in nanomaterials smaller than the wavelength of light. The team engineered an all-solid-state system that leverages ultra-bright upconverting nanoparticles and microlaser expertise recently developed at the Foundry, along with high quality factor arrays of silver (Ag) nanoparticles fabricated by the users.

The coherent coupling between Ag nanoparticles selectively enhances the emission of the lanthanide ion-doped UCNPs, enabling the ultra-low lasing thresholds. The plasmonic nanolasers exhibit highly directional lasing at an extremely low threshold of 29 W/cm2 and are stable for longer than 6 hours.

These nanolasers exhibit the lowest ever lasing threshold compared to other plasmon or upconverting nanolasers, and offer the rare combination of stable, continuous-wave operation at room temperature. The lasers are excited with infrared light, whose low energy minimizes damage to the environments where small lasers are needed. These robust, low power lasers are small enough to function within tissue, smartphones, or on-chip quantum circuitry, enabling applications in medicine, nanophotonics, and quantum information science.