Measuring milk fat content by random laser emission

Abstract

The luminescence spectra of milk containing rhodamine 6G are shown to exhibit typical signatures of random lasing when excited with 532 nm laser pulses. Experiments carried out on whole and skim forms of two commercial brands of UHT milk, with fat volume concentrations ranging from 0 to 4%, presented lasing threshold values dependent on the fat concentration, suggesting that a random laser technique can be developed to monitor such important parameter.

Random Lasing from Label-Free Living Cells for Rapid Cytometry of Apoptosis

“…Biolasers are a leading edge technology that has recently attracted attention because of its potential biomedical and biological applications, for example, cell tagging, imaging, and diagnosis. − Compared with traditional biological fluorescent emissions, biolasing is advantageous because of its threshold-gate behavior, narrow line width, and directional out-coupling. − Over the past few years, various optical systems have been designed to provide optical feedback for biolasers such as Fabry–Perot, whispering gallery mode, and random lasers. − Among them, random lasing was achieved by strong multiple scatterings of light in disordered gain media rather than a fixed cavity. − The ability to generate lasing in biological materials without external cavities is definitely an advantage. Recently, different gain-medium-infiltrated biological materials, such as disordered protein crystals, marine, skeleton, human colon tissues, and interestingly, living cell suspensions, have been shown to support random lasing action. − In particular, the spectral characteristics of random lasing are strongly dependent on the scattering properties of the biological host material, − providing a promising tool for the characterization of biophysical properties. However, applying random lasing to biopsies is still challenging, considering the poor biocompatibility of laser dyes and the limited understanding of the intercellular and intracellular biophysical properties. − …”

Direct Measurement of the Reduced Scattering Coefficient by a Calibrated Random Laser Sensor

“…The main features of the random laser have been reported for the first time in the pioneering theoretical work of Letokhov [ 2 ] at the end of 1960s and experimentally realized since the 1990s in laser dye with nanoparticles [ 3 ], polymer films [ 4 ], organic media [ 5 ], laser crystal powder [ 6 ], cold atoms [ 7 ], semiconductor powder [ 8 ], dye-infiltrated biological tissue [ 9 ], optical fibers [ 10 , 11 , 12 ], stimulated Raman scattering [ 13 ], liquid crystals [ 14 , 15 , 16 ], plasmonics [ 17 , 18 ], dye-infiltrated opals [ 19 ], and perovskite [ 20 ]. The characteristics of the random laser have been extensively studied during the last three decades, and applications have been proposed, in particular in the fields of sensing [ 21 , 22 , 23 , 24 , 25 , 26 ], illumination [ 27 , 28 , 29 , 30 ], spectroscopy [ 31 ], optical networks [ 32 , 33 ], the statistics of events and fluctuations [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ], replica symmetry breaking phenomenology [ 44 , 45 , 46 , 47 , 48 ,…”

Random Laser Spectral Fingerprinting of Lithographed Microstructures

“…The highest emission intensity of non‐coherent RLs with respect to the spontaneous emission of common fluorophores has been widely employed in sensing applications by taking advantage of the lasing threshold dependence on external parameters, such as pH, [ 8 ] temperature, [ 9 ] or presence of specific molecules. [ 10,11 ] On the other side, spectral coherence is highly attractive due to the specificity of the emission that is directly determined by the nature of the scattering elements which affects the spatial extent of the electromagnetic modes and in turn the spectral features. This aspect makes coherent RLs particularly suitable for advanced applications for which a unique spectral signature is needed, ranging from cancer cell screening [ 12,13 ] to the realization of anti‐counterfeiting labels.…”