Deeply Subwavelength Blue-Range Nanolaser

Modern high-definition display and augmented reality technologies require the development of ultracompact micro- and nano-pixels with colors covering the full gamut and high brightness. In this regard, lasing nano-pixels emitting light in the spectral range 400-700 nm are highly demanded. Despite progress in red, green, and ultraviolet nanolasers, the demonstrated blue-range (400-500 nm) single-particle-based lasers are still not subwavelength yet. Here we fabricate CsPbCl$_3$ cubic-shaped single-crystal nanolasers on a silver substrate by wet chemistry synthesis, producing their size range around 100-500 nm, where the nanoparticle with sizes 0.145$\mu$m$\times$0.195$\mu$m$\times$0.19$\mu$m and volume 0.005 $\mu$m$^3$ (i.e. $\sim\lambda^3$/13) is the smallest nanolaser among the lasers operating in the blue range reported so far, with emission wavelength around $\lambda\approx 415$ nm. Experimental results at a temperature of 80 K and theoretical modeling show that the CsPbCl$_3$ nanolaser is a polaritonic laser where exciton-polaritons are strongly coupled with Mie resonances enhanced by the metallic substrate. As a result, the combination of the strong excitonic response of CsPbCl$_3$ materials, its high crystalline quality, and optimized optical resonant properties resulting in a population-inversion-free lasing regime are the key factors making the proposed nanolaser design superior among previously reported ones in the blue spectral range.