Letter to the editor: The 2021 Physics Nobel Prize and the understanding of complex physical systems

The 2021 Physics Nobel Prize was awarded to Syukuro Manabe, Klaus Hasselmann, and Giorgio Parisi for their “groundbreaking contributions to our understanding of complex physical systems.” Here we review some of the ideas and results which served as the scientific basis to the award. We also comment on the works by our research group on the complex systems properties of random lasers and random fiber lasers.

Characteristics of Dye-doped Silica Nanoparticles- Based Random Lasers in the Air and Water

Random lasers based on dye-doped silica nanoparticles are attracted for biomedical applications due to their biocompatibility and high brightness. Several laser structures including silica powder and film have been reported. However, the dependence of lasing characteristics including lasing threshold and emission wavelength on the laser size and working environment have not been explored. Here, we demonstrate and compare the lasing characteristics of dye-doped silica random lasers in air and water. These lasers present in thin structures, the so-called microslices, with a thickness of 1 µm and various dimensions from 30 to 300 µm. It is found that the lasing threshold (Ith) decreases with increasing laser size such as for sample in the air and for sample in water, where A the sample surface area. For a similar size, the lasing threshold of the sample in water is about 3-8 times higher than that of the sample in the air. In addition, the lasing peak wavelength exhibits a red-shift with increasing laser size. In the air, a shift of 8 nm is recorded when the sample surface area increases from 21×103 to 169×103 µm2. Furthermore, for a similar size, the lasing wavelength of the sample in the air is also red-shifted (13 nm in average ) compared with that of the sample in water. Our finding provides useful information for the use of silica-based random lasers in bioimaging and biosensing applications.

Photosensitive Yb-Doped Germanophosphosilicate Artificial Rayleigh Fibers as a Base of Random Lasers

Asingle-mode Yb-doped germanophosphosilicate fiber with ultra-low optical losses (less than 2 dB/km) was fabricated by means of the MCVD method utilizing an all-gas-phase deposition technique developed “in house”. The absorption and luminescent spectral properties of the fiber were thoroughly studied. The photosensitivity of the pristine (non-hydrogenated) fiber to 248 nm-laser radiation was confirmed by means of fiber Bragg grating (FBG) inscription directly during the drawing process. The random single-frequency lasing at the 1060-nm-wavelength obtained in the 21-m-long fiber with an array of weak FBG was reported. The developed laser slope efficiency in the backward-pumping scheme was measured as high as 32%.

Waveguided nematic liquid crystal random lasers

In waveguided nematic liquid crystal random lasers (NLCRLs), we realize polarized random laser (RL) emission and discover that the waveguide effect reduces the transmission loss of the RL whose polarization is parallel to the liquid crystal molecules (LCMs). Compared with the traditional liquid crystal random lasers, the waveguide NLCRLs can achieve the regulation of RLs strength, polarization, and wavelength in the same structure. The electric field can drive the rotation of LCMs to control the RL polarization and intensity. The drop of horizontal polarization laser and the increase of vertical polarization laser prove the role of the waveguide effect. In addition, the disorder of the waveguided NLCRLs is highly sensitive to temperature, which makes it easy to control the wavelength and intensity of the RL. As the temperature rises, the waveguide effect is weakened, resulting in a weakening of the restriction along liquid crystal (LC) cell normal direction. The reduced laser intensity verifies the role of the waveguide effect.