Replica symmetry breaking in 1D Rayleigh scattering system: theory and validations.

Spin glass theory, as a paradigm for describing disordered magnetic systems, constitutes a prominent subject of study within statistical physics. Replica symmetry breaking (RSB), as one of the pivotal concepts for the understanding of spin glass theory, means that under identical conditions, disordered systems can yield distinct states with nontrivial correlations. Random fiber laser (RFL) based on Rayleigh scattering (RS) is a complex disordered system, owing to the disorder and stochasticity of RS. In this work, for the first time, a precise theoretical model is elaborated for studying the photonic phase transition via the platform of RS-based RFL, in which we clearly reveal that, apart from the pump power, the photon phase variation in RFL is also an analogy to the temperature term in spin-glass phase transition, leading to a novel insight into the intrinsic mechanisms of photonic phase transition. In addition, based on this model and real-time high-fidelity detection spectral evolution, we theoretically predict and experimentally observe the mode-asymmetric characteristics of photonic phase transition in RS-based RFL. This finding contributes to a deeper understanding of the photonic RSB regime and the dynamics of RS-based RFL.

Ultrahigh-sensitive and compact temperature sensor based on no-core fiber with PMMA coating.

A new mechanism between the temperature sensitivity and the length ratio of PMMA coating to no-core fiber (NCF) is reported to realize an optical fiber temperature sensor with ultra-high sensitivity and compact size by PMMA-coated no-core fiber. By both theory and experiment, it is found that the sensitivity has a linear response to the length ratio of PMMA coating to NCF rather than the conventional viewpoint that it depends on the length of PMMA. Based on this conclusion and the high thermo-optic coefficient of PMMA, the temperature sensitivity is significantly enhanced as high as -9.582 nm/℃ through a simple, compact, and inexpensive sensor with 5 mm NCF and 3 mm PMMA coating. Our work opens a new avenue of a significant increase in the detection sensitivity of miniaturized fiber temperature sensors.