Polyethylene terephthalate cubic nonlinearity coefficient measurement with a modified Z-scan technique

Area of Science:

• Nonlinear Optics
• Materials Science
• Laser Physics

Background:

• Polyethylene terephthalate (PET) is a widely used polymer with potential applications in nonlinear optics.
• Accurate measurement of nonlinear optical coefficients is essential for developing advanced optical materials and devices.
• Traditional Z-scan techniques may lack the sensitivity required for materials with low damage thresholds, such as PET.

Purpose of the Study:

• To measure the nonlinear refractive index (n2) of PET at 1030 nm and 515 nm using a modified Z-scan technique.
• To evaluate the performance and sensitivity of the modified Z-scan method.
• To report the nonlinear coefficient of PET at 515 nm, potentially for the first time.

Main Methods:

• A modified Z-scan technique was developed and employed.
• Measurements were performed on polyethylene terephthalate (PET) and fused silica (FS) samples.
• The nonlinear refractive index (n2) was determined at two different wavelengths (1030 nm and 515 nm).

Main Results:

• The modified Z-scan technique demonstrated a threefold improvement in sensitivity compared to the traditional method.
• Measured n2 values for fused silica at 1030 nm and 515 nm agreed with literature values.
• The nonlinear refractive index for PET was measured as 11.5 x 10^-7 cm^2/GW at 1030 nm and 26.5 x 10^-7 cm^2/GW at 515 nm.
• The obtained n2 value for PET at 515 nm is reported for the first time and indicates high nonlinearity in the visible spectrum.

Conclusions:

• The modified Z-scan technique is highly effective for measuring the nonlinear optical properties of materials like PET, especially those with low damage thresholds.
• PET exhibits significant nonlinear optical behavior, particularly in the visible wavelength range.
• The enhanced sensitivity of the modified Z-scan method is critical for accurate characterization of novel optical materials.