A new class of optical sensors: a random laser based device

TLDR

Random lasers use scattering for optical feedback, making their emission highly sensitive to scattering details and thus suitable for sensing disordered media, but existing methods require toxic additives that alter the medium and are unsuitable for in‑vivo use. The authors introduce a random‑laser‑based sensor that avoids these drawbacks by separating gain from diffusion. The sensor achieves this separation by employing a design that decouples the gain medium from the diffusive scattering region. Experimental characterization with a diffusive liquid phantom shows that, relative to a passive method, the sensor exploits the random laser’s gain and spectral properties to improve sensing performance.

Abstract

Abstract In a random laser the optical feedback is provided by scattering rather than by an optical cavity. Then, since its emission characteristics are very susceptible to the scattering details, it is a natural candidate for making active sensors to use as a diagnostic tool for disordered media like biological samples. However, the methods reported up to now, requiring the injection of toxic substances in the sample, have the drawback of altering the physical-chemical composition of the medium and are not suitable for in-vivo measurements. Here we present a random laser based sensor that overcomes these problems by keeping gain and diffusion separated. We provide an experimental characterisation of the sensor by using a reference diffusive liquid phantom and we show that, compared to a passive method, this sensor takes advantage of the gain and spectral properties of the random laser principle.