Optical limiting for microsecond pulses

Area of Science:

• Nonlinear optics
• Quantum optics
• Materials science

Background:

• Fullerene C(60) exhibits significant optical limiting properties.
• Understanding nonlinear absorption dynamics is crucial for optical limiting applications.

Purpose of the Study:

• To present a dynamical theory for microsecond laser pulse propagation and nonlinear absorption.
• To investigate the primary mechanisms of nonlinear absorption in fullerene C(60).
• To analyze the role of pulse propagation in optical power limiting.

Main Methods:

• Developed a dynamical theory for nonlinear absorption and propagation.
• Applied the theory to fullerene C(60) using coupled rate equations.
• Reduced rate equations to a single dynamical equation for ground state population.
• Numerically solved the paraxial field equation and rate equation.

Main Results:

• Sequential absorption via triplet-triplet transitions is the dominant nonlinear absorption mechanism in C(60).
• An adiabatic approximation simplifies the rate equations.
• Pulse propagation significantly impacts optical power limiting by altering absorption processes.
• Nonlinear absorption weakens, transitioning to linear absorption as the pulse propagates.

Conclusions:

• The developed dynamical theory accurately describes nonlinear absorption and propagation in fullerene C(60).
• Triplet-triplet absorption is the main contributor to optical limiting.
• Propagation effects are critical for optimizing optical power limiting devices.