Abstract
The research in optical sensors has been largely encouraged by the demand for low-cost and less or non-invasive new detection strategies. The invention of the random laser has opened a new frontier in optics, providing also the opportunity to explore new possibilities in the field of sensing, besides several different and peculiar phenomena. The main advantage in exploiting the physical principle of the random laser in optical sensors is due to the presence of the stimulated emission mechanism, which allows amplification and spectral modification of the signal. Here, we present a step forward in the exploitation of this optical phenomenon by a revisitation of a previous experimental setup, as well as the measurement method, in particular to mitigate the instability of the results due to shot-to-shot pump energy fluctuations. In particular, the main novelties of the setup are the use of optical fibers, a reference sensor, and a peristaltic pump. These improvements are devoted to: eliminating optical beam alignment issues; improving portability; mitigating the variation in pump energy and gain medium performances over time; realizing an easy and rapid change of the sensed medium. The results showed that such a setup can be considered a prototype for a portable device for directly measuring the scattering of liquid samples, without resorting to complicated numerical or analytic inversion procedures of the measured data, once the suitable calibration of the system is performed.
Highlights
Random lasing [1] is a physical phenomenon that generates a special kind of optical radiation, with mixed properties between common light and laser one
Random lasing is a process whose temporal dynamics begins, in general, with a pump pulse that excites the gain medium; once the first emitted photons are generated by spontaneous emission, the energy stored in the medium, in the presence of enough scattering, undergoes depletion by the mechanism of stimulated emission
As in a conventional laser, for a random laser system, the threshold energy can be defined, in a nutshell, in the conditions that allow the gain to overcome the losses; the critical difference consists of the fact that the threshold in a random laser depends on the scattering strength, because, in the absence of an optical cavity, it is the mechanism that can support the feedback
Summary
Random lasing [1] is a physical phenomenon that generates a special kind of optical radiation, with mixed properties between common light and laser one. In a random laser system, the last of these three elements, which allows the radiation to spend a long enough time inside the gain medium for the amplification, is missing. Random lasing is a process whose temporal dynamics begins, in general, with a pump pulse that excites the gain medium; once the first emitted photons are generated by spontaneous emission, the energy stored in the medium, in the presence of enough scattering, undergoes depletion by the mechanism of stimulated emission. As in a conventional laser, for a random laser system, the threshold energy can be defined, in a nutshell, in the conditions that allow the gain to overcome the losses; the critical difference consists of the fact that the threshold in a random laser depends on the scattering strength, because, in the absence of an optical cavity, it is the mechanism that can support the feedback
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
