Abstract
Intensity fluctuations in lasers are commonly studied above threshold in some special configurations (especially when emission is fed back into the cavity or when two lasers are coupled) and related with their chaotic behaviour. Similar fluctuating instabilities are usually observed in random lasers, which are open systems with plenty of quasi-modes whose non orthogonality enables them to exchange energy and provides the sort of loss mechanism whose interplay with pumping leads to replica symmetry breaking. The latter however, had never been observed in plain cavity lasers where disorder is absent or not intentionally added. Here we show a fluctuating lasing behaviour at the lasing threshold both in solid and liquid dye lasers. Above and below a narrow range around the threshold the spectral line-shape is well correlated with the pump energy. At the threshold such correlation disappears, and the system enters a regime where emitted laser fluctuates between narrow, intense and broad, weak peaks. The immense number of modes and the reduced resonator quality favour the coupling of modes and prepares the system so that replica symmetry breaking occurs without added disorder.
Highlights
Parameter that was later on proven to bear a physical meaning[16] and the phenomenon has ever since been referred to as the replica symmetry breaking
Replica symmetry breaking was so far observed only in random lasers (RL) because they provide a collection of light modes whose emissions are equivalent and susceptible to frustration
In this work we demonstrate a fluctuating behaviour at the threshold region of lasers made from pure liquid dye solution in a cuvette and dye doped DNA films without adding any scatterers
Summary
The dynamics of the single mode laser field as it interacts with the lasing medium has been examined in the context of non-equilibrium statistical mechanics so that a laser near threshold can find a close parallel in the order/ disorder phase transition of a pure fluid vapour-liquid second order phase transitions. In the threshold energy range (101 μJ in Fig. 4 upper row) the distribution is totally different with two strong maxima at q = ±1 and a largely depleted region around q = 0 pointing to a one-step RSB In these circumstances where emission consists of broad weak peaks and narrow, intense lasing pulses if the statistical analysis is performed after separating both kinds of spectra, two differing statistics are found: weak peaks obey a replica symmetric zero-centred distribution while intense laser bursts follow a one-step RSB distribution with high density at q = 0 (refer to SI Fig. S6). The ease of fabrication and the simplicity of sample preparation may bring a large variety of application such as use in security marker and photonic displays or even in random number generation
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