Index-of-refraction change in optically pumped solid-state laser materials

Area of Science:

• Laser Physics
• Materials Science
• Nonlinear Optics

Background:

• Neodymium (Nd3+)-doped materials are crucial for laser applications.
• Understanding refractive index changes is vital for laser amplifier design.
• Thermal effects are a known source of beam distortion in lasers.

Purpose of the Study:

• To investigate population-induced changes in refractive index in Nd3+-doped laser materials.
• To quantify the polarizability change associated with Nd3+ ions in different energy states.
• To compare the impact of population-induced refractive index changes with thermal effects on beam distortion.

Main Methods:

• Degenerate four-wave mixing (DFWM) measurements.
• Resonant pumping of Nd3+ ions.
• Absolute signal strength measurements.

Main Results:

• The dominant signal contribution arises from the difference in polarizability between ground and metastable states of Nd3+ ions.
• A laser-induced polarizability change of approximately 0.01-0.05 ų was determined.
• Population-induced refractive index changes were found to be comparable to thermal distortions in single-shot laser amplifiers.

Conclusions:

• Population dynamics significantly influence the refractive index in Nd3+-doped laser materials.
• The observed polarizability changes are a key factor in laser beam distortion.
• Minimizing population-induced refractive index changes may be as important as managing thermal effects for high-power laser systems.