Replica Symmetry Breaking in a Weakly Scattering Optofluidic Random Laser

Abstract

We report the observation of replica symmetry breaking (RSB) in a weakly scattering optofluidic random laser (ORL). Coherent random lasing is indicated by the presence of narrow peaks rising out of the spectral background. This coherence helps to identify a random laser threshold, which is expected to be gradual with weak scattering. We find that lasing action initiated using optical pulsed pumping coincides with the onset of both RSB and Lévy flight statistics. However, the transition from the photonic paramagnetic to photonic glass phase is more subtle in that the Parisi overlap function broadens instead of completely changing shape. This subtlety is balanced by an accompanying result of identical experimental conditions giving rise to lasing or no lasing depending on the shot. Additional statistical calculations and investigations into the fundamental physical mechanisms present in the ORL support this conclusion. Using simple numerical models, we study the critical spectral properties required for RSB to occur, as indicated by the Parisi overlap function. The simplicity of the models helps demonstrate the sensitive nature of this tool and the necessity of additional verification of the physical mechanisms present in the experiment. Random lasers are a special class of active disordered materials where laser oscillations survive due to the optical feedback provided by multiple scattering 1,2. Random lasers are spectrally distinguished from conventional lasing systems by randomly distributed sharp spikes over the emission. These sharp spikes can be directly attributed to resonances known as quasi bound (QB) states (e.g. 3,4) of the passive cavity when the strength of scattering is strong 5. On the contrary, weakly scattering systems exhibit spatially extended QB states. One-to-one correspondence exists between QB states and lasing modes only at the lasing threshold, only if that threshold is small enough 5 , and only if the pumped region includes the entire spatial area over which the QB states extend 6. When such correspondence breaks down, lasing modes can be described as a mixture of QB states; for example, as scattering becomes very weak. Despite the absence of correspondence with a single QB state, these lasing modes retain the spatial properties of the QB states from which they are composed. Such states exhibit strong spatial overlap, short lifetimes, and strong leakage at the boundary due to their extended nature. This gives rise to mode competition and strong intermodal coupling via spatial hole burning 7,8 , which can result in chaotic behavior with different emission spectra observed pump shot to pump shot 9. Insight into shot-to-shot fluctuations has been provided by spin glass theory 10,11. The replica symmetry breaking (RSB) phase transition was observed experimentally 12 and the theoretical connection between intensity and complex amplitude fluctuations established 13. According to spin glass theory, the statistical distribution of an overlap parameter q, namely the Parisi overlap function P(q), c...

Random Laser Spectral Fingerprinting of Lithographed Microstructures

“…Same value is obtained for the Nd:Yag laser line employed as pump source measured in the same conditions and showing the good coherence degree of the RL peaks. The spectra are stable and do not show significant shot to shot fluctuations in the emission differently from other systems, [ 41–43 ] as shown in Figure 3B where single shot spectra taken at different times and from the same system result identical within the spectral resolution. The evolution of the spectral emission by varying the input energy is reported in Figure 3C, showing spectral features that become narrower with increasing pump energy, as also evidenced by the decrease of the full width half maximum (FWHM) of one representative peak versus pump energy.…”

Heterogeneous Random Laser with Switching Activity Visualized by Replica Symmetry Breaking Maps

“…To better understand the nature of the bright regions and for a visualization of their activity, we built replica symmetry breaking (RSB) maps from the fluorescence images. Replica symmetry breaking in random lasers has been introduced in 2015 and widely demonstrated in the last years both theoretically and experimentally for several kinds of RLs. − It has been identified at and above the laser threshold and quantified by the bimodal distribution of the Parisi overlap parameter. , …”

“…Replica symmetry breaking in random lasers has been introduced in 2015 17 and widely demonstrated in the last years both theoretically and experimentally for several kinds of RLs. [19][20][21][22][23][24][25][26] It has been identified at and above the laser threshold and quantified by the bimodal distribution of the Parisi overlap parameter. 27,28 Published in ACS Photonics, doi: 10.1021/acsphotonics.0c01803 (2021).…”

Simultaneous evaluation of intermittency effects, replica symmetry breaking and modes dynamics correlations in a Nd:YAG random laser

“…Although RLs are cavity-less, they are not modeless, and this feature has instigated a great deal of theoretical and experimental research, showing that a RL is in fact a multimode laser 39 – 47 . One of the statistical tools employed to analyze modes correlations in photonic systems is the Pearson correlation coefficient.…”

“…More recently, Sciuti and co-workers 46 studied the modes dynamics in the mode-locking transition via the temporal mapping of the emitted spectra characterized by the Pearson correlation in a RL based on dye-doped electrospun nanofibers. Also, Sarkar and co-workers related 47 the modes correlations to the RSB and Lévy-like properties of a weakly scattering optofluidic RL. Additionally, our group have also recently applied the Pearson analysis to a hybrid electronically addressable random fiber laser 48 .…”