Shrinking Ultra-Pure Visible Lasers onto a Microchip

Creating precise, narrow-linewidth light in the visible spectrum usually demands a laboratory filled with bulky equipment. This limitation has long hindered the miniaturisation of quantum technologies. However, researchers have now successfully developed an on-chip visible Brillouin-quadratic microlaser, condensing high performance into a disk merely 117 micrometres in diameter.

The device utilises thin-film lithium niobate (TFLN), a material celebrated for its non-linear optical capabilities. Through precise dispersion engineering, the team achieved an ultra-high optical Q factor—a measure of the cavity's ability to trap light—of 4.0×10⁶. This environment fosters a strong interaction between photons (light) and phonons (vibrational energy).

Consequently, the microdisk generates simultaneous Stokes Brillouin lasing and its second harmonic (frequency-doubled light) with a remarkably low power threshold of just 1.81 mW. Boasting intrinsic linewidths as narrow as 864 Hz for the visible output, this breakthrough paves the way for on-chip quantum information processing and precise metrology without the need for heavy hardware.