Cyano-Based Materials with Giant Optical Anisotropy and Second Harmonic-Generation Effect.

Area of Science:

• Materials Science
• Optics
• Solid State Chemistry

Background:

• Achieving giant optical anisotropy (birefringence) across infrared (IR) to ultraviolet (UV) spectroscopy is challenging due to the scarcity of ideal optical motifs.
• Polar motifs with large optical anisotropy are rare in nonlinear optical (NLO) materials, limiting strong second harmonic generation (SHG) and phase-matching capabilities.

Purpose of the Study:

• To identify and investigate novel motifs for advanced NLO materials with broad spectral applicability.
• To explore the potential of the one-dimensional chained cyano (CN) motif as a fundamental building block for NLO materials.

Main Methods:

• Analysis of microstructure and macro optical properties.
• Theoretical investigation of the cyano (CN) motif's optical anisotropy and NLO response.
• Integration of the CN motif into various coordination structures (metal cyanides, cyanogen halides, cyanogen chalcogenides).

Main Results:

• The one-dimensional chained cyano (CN) motif demonstrates substantial optical anisotropy and SHG effect from the IR to UV regions.
• CN-based compounds exhibit tunable NLO capabilities across IR, UV, and deep-UV spectra.
• The experimentally obtained chained acentric CNI structure shows a large SHG effect (~17 pm/V) and giant optical birefringence (~0.7 at 1064 nm).

Conclusions:

• The cyano (CN) motif is identified as a novel, previously overlooked NLO material gene.
• Cyano-based compounds offer a promising route to enrich structural chemistry and advance the optical material genome project.
• These findings pave the way for developing new optical materials with tunable NLO properties for diverse spectroscopic applications.