Self-defocusing in CdSe induced by charge carriers created by two-photon absorption

Area of Science:

• Optics and Photonics
• Semiconductor Physics

Background:

• Nonlinear optical effects in semiconductors are crucial for advanced photonic applications.
• Understanding the mechanisms behind nonlinear refraction is key to controlling light-matter interactions.

Purpose of the Study:

• To investigate and characterize the self-defocusing of picosecond laser pulses in cadmium selenide (CdSe).
• To quantify the effective nonlinear refractive index in CdSe and compare it with established nonlinear materials.
• To validate a theoretical model explaining the observed nonlinear optical phenomena.

Main Methods:

• Experimental observation of self-defocusing using picosecond, 1.06-micrometer laser pulses.
• Measurement of the effective nonlinear refractive index.
• Theoretical modeling based on charge carrier generation via two-photon absorption.

Main Results:

• Observed significant self-defocusing of picosecond pulses in CdSe.
• Determined an effective nonlinear refractive index up to two orders of magnitude greater than that of carbon disulfide (CS(2)).
• Achieved good agreement between experimental results and the theoretical model.

Conclusions:

• The dominant mechanism for self-defocusing in CdSe under these conditions is attributed to photogenerated charge carriers.
• Cadmium selenide exhibits exceptionally strong nonlinear optical properties, making it a promising material for photonic devices.
• The theoretical framework provides a reliable explanation for nonlinear refraction driven by two-photon absorption in semiconductors.