Comparative study on three highly sensitive absorption measurement techniques characterizing lithium niobate over its...

Area of Science:

• Materials Science
• Optical Spectroscopy
• Solid State Physics

Background:

• Lithium niobate (LiNbO3) is a critical material in photonics and nonlinear optics.
• Accurate characterization of its optical absorption is essential for device performance.
• Previous studies lacked comprehensive absorption spectra across its entire transparency window.

Purpose of the Study:

• To comparatively measure the absorption coefficient of undoped, congruently grown lithium niobate.
• To cover the broad wavelength range from 390 to 3800 nm.
• To provide a complete absorption spectrum of lithium niobate's transparency window.

Main Methods:

• Utilized three independent, high-sensitivity spectrometers: photoacoustic, photothermal common-path interferometer, and whispering-gallery-resonator-based.
• Measured absorption for both ordinary and extraordinary polarized light.
• Extended measurements to the Urbach tail and multiphonon edge using grating and FTIR spectrometers.

Main Results:

• Determined absorption coefficients ranging from <10⁻⁴ cm⁻¹ to 2 cm⁻¹.
• Generated the first complete absorption spectrum for lithium niobate across its entire transparency window.
• Achieved good agreement between the three independent measurement techniques.

Conclusions:

• The employed spectroscopic methods provide reliable and accurate absorption coefficient data for lithium niobate.
• This comprehensive dataset is vital for optimizing lithium niobate-based optical devices.
• The study establishes a benchmark for optical absorption characterization in transparent materials.