Alice Boschetti
LENS
Alice Boschetti is a PhD student at LENS in Florence, Italy, working in the group of professor D. S. Wiersma. The group is interested in the optical properties of complex photonic structures, like photonic crystals and disordered materials. In particular, her PhD work focusses on the study of random lasers for spectroscopic applications. Recently, she was able to realize the experimental high resolution characterization of the transmission function of a synthetic filter using an optically pumped random laser. Alice received her master degree in Physics from the University of Florence with a thesis on quantum dots.
Well-established examples of super-resolved microscopy, as STORM, PALM and FPALM, allow to reconstruct images with higher resolution than that imposed by the diffraction limit. These methods are based on the sequential... [ view full abstract ]
Well-established examples of super-resolved microscopy, as STORM, PALM and FPALM, allow to reconstruct images with higher resolution than that imposed by the diffraction limit. These methods are based on the sequential activation and time-resolved localization of fluorophores. During imaging, only an optically resolvable subset of fluorophores is activated, and the position of each fluorophore can be determined with high precision by finding its centroid. Subsequent iterations allow the localization of large numbers of fluorophores, creating a super-resolved image of the sample. The aim of this work is to export this concept to the spectral domain, that is, to obtain a highly resolved spectrum of a given sample, whose spectral features are well below the spectral resolution of the measuring spectrometer.
Ideally, to perform this analysis, a tunable laser can be used as a source. In this case, the target spectrum can be retrieved simply by combining the transmission amplitude at each input frequency, with the final spectral resolution being limited only by the spectral width of the illumination source. Here, we demonstrate that the tunable laser input source can be conveniently replaced by a much more cost-effective random laser.
Random lasers are laser sources using a highly disordered gain medium. It has no optical cavity, but the principles of operation are the same of a laser. An optically pumped random laser can easily be obtained suspending scattering nano-particles such as titanium dioxide or zinc oxide in a dye solution. At each pump laser shot, only few modes rise above the lasing threshold as determined by mode competition and gain depletion. Due to the intrinsic, dynamic disorder of the suspension, such single-shot spectra are entirely uncorrelated, with narrow peaks appearing at independent frequencies.
We simulate a measurement of the transmitted frequency response of a Fabry-Perot (F-P) filter and a Fibonacci-1D crystal (Fig.1) with fine spectral features below the finite resolution of the spectrometer. The statistical reconstruction of their transmittance curves relies on the stochastic intensity fluctuations of the random laser modes, which allows only few of them to be excited at each pump pulse.
