Thermo-optic coefficients study in KGd(WO4)2 and KY(WO4)2 by a modified minimum deviation method

Area of Science:

• Solid State Physics
• Materials Science
• Optics

Background:

• Potassium (rare-earth) double tungstates are important laser materials.
• Understanding their thermo-optic properties is crucial for laser design and performance.
• Anisotropic thermal expansion can affect optical measurements.

Purpose of the Study:

• To characterize the thermo-optic coefficients anisotropy in KGd(WO4)2 and KY(WO4)2 crystals.
• To investigate the influence of anisotropic thermal expansion on these measurements.
• To provide accurate thermo-optic data for these materials in the visible spectral range.

Main Methods:

• A modified minimum deviation method was employed for accurate measurements.
• The method accounted for sample shape and dimension changes due to anisotropic thermal expansion.
• Measurements were conducted in the spectral range of 0.44-0.63 μm at room temperature.

Main Results:

• Principal refractive indices and optical axes positions were determined for both KGdW and KYW crystals at 633 nm.
• All measured thermo-optic coefficients (dn/dT) for both crystals were negative.
• Specific values for dn(p)/dT, dn(m)/dT, and dn(g)/dT were reported for KGdW and KYW at 633 nm.

Conclusions:

• The study successfully characterized the thermo-optic coefficients anisotropy in KGdW and KYW.
• The developed modified minimum deviation method accurately addresses anisotropic thermal expansion effects.
• The obtained negative thermo-optic coefficients are vital data for optical material applications and laser development.