Large fluctuations at the lasing threshold of solid- and liquid-state dye lasers

Area of Science:

• Laser Physics
• Nonlinear Optics
• Condensed Matter Physics

Background:

• Intensity fluctuations in lasers are typically studied above threshold, often linked to chaotic behavior in coupled or feedback systems.
• Similar instabilities are observed in random lasers, attributed to quasi-mode interactions and replica symmetry breaking.
• Such fluctuations have not been previously documented in conventional cavity lasers without intentional disorder.

Purpose of the Study:

• To investigate fluctuating lasing behavior in standard cavity lasers at the lasing threshold.
• To determine if replica symmetry breaking can occur in lasers without added disorder.
• To characterize the spectral properties of laser emission around the threshold.

Main Methods:

• Experimental observation of lasing behavior in solid and liquid dye lasers.
• Analysis of spectral line-shape and its correlation with pump energy.
• Characterization of intensity fluctuations at the lasing threshold.

Main Results:

• A fluctuating lasing behavior was observed at the lasing threshold in both solid and liquid dye lasers.
• Above and below the threshold, spectral line-shape correlated with pump energy.
• At the threshold, this correlation vanished, leading to fluctuations between narrow, intense, and broad, weak spectral peaks.
• Replica symmetry breaking was observed without the need for added disorder, facilitated by mode coupling and reduced resonator quality.

Conclusions:

• Fluctuating lasing behavior and replica symmetry breaking can occur in conventional cavity lasers at the lasing threshold.
• The interplay of numerous modes and reduced resonator quality in dye lasers promotes mode coupling, enabling these phenomena without external disorder.
• This finding challenges previous assumptions about the conditions required for replica symmetry breaking in laser systems.