Characterizing large-area electro-optic crystals toward two-dimensional real-time terahertz imaging.

Area of Science:

• Materials Science
• Optics
• Terahertz (THz) Technology

Background:

• Homogeneity of large-area crystals is crucial for advanced imaging techniques.
• Nonuniform birefringence and scattering can degrade signal quality in terahertz (THz) imaging.
• Cadmium telluride (CdTe) and zinc telluride (ZnTe) are potential materials for THz applications.

Purpose of the Study:

• To characterize the spatial homogeneity of large-area CdTe(110) and ZnTe(110) crystals.
• To evaluate their suitability for two-dimensional electro-optic THz imaging.
• To identify factors affecting crystal homogeneity and THz signal quality.

Main Methods:

• Raster electro-optic scanning was employed to assess crystal uniformity.
• Terahertz (THz) signals at 0.2 THz (CdTe) and 0.645 THz (ZnTe) were analyzed.
• A hybrid measurement system with a fs Nd:glass laser and a continuous-wave electronic THz source was utilized.

Main Results:

• Spatial variations in THz signal were attributed to nonuniform residual birefringence and scattering.
• For CdTe, homogeneity was critically dependent on the crystal growth method and influenced by slip planes.
• The highest-quality CdTe(110) crystals exhibited root-mean-square (rms) signal variations below 15%, comparable to ZnTe(110).

Conclusions:

• Large-area CdTe(110) and ZnTe(110) crystals can achieve homogeneity suitable for 2D electro-optic THz imaging.
• Crystal growth method optimization is essential for achieving high-quality CdTe for THz applications.
• The developed hybrid electro-optic scanning system effectively assesses crystal homogeneity for THz imaging.