Strong Kleinman-forbidden second harmonic generation in chiral sulfide: La4InSbS9

Area of Science:

• Solid-state chemistry and materials science
• Nonlinear optics and photonics

Background:

• Chiral materials are crucial for advanced optical applications.
• Second harmonic generation (SHG) is a key nonlinear optical phenomenon.
• Developing new materials with strong, phase-matchable SHG is an ongoing challenge.

Purpose of the Study:

• To synthesize and characterize a novel family of chiral sulfides, Ln(4)InSbS(9).
• To investigate the second harmonic generation (SHG) properties of these new compounds.
• To explore the theoretical origins of observed SHG effects.

Main Methods:

• Solid-state reaction synthesis of Ln(4)InSbS(9) (Ln = La, Pr, Nd).
• Structural characterization using X-ray diffraction (implied by space group determination).
• Experimental measurement of second harmonic generation (SHG) intensity and phase-matching properties.
• Computational analysis using density functional theory (DFT) and ab initio molecular dynamics.

Main Results:

• A new chiral sulfide family, Ln(4)InSbS(9), with a unique structure type (P4(1)2(1)2 or P4(3)2(1)2) was successfully synthesized.
• The lanthanum (La) member demonstrated the strongest Kleinman-forbidden SHG effect reported to date, exceeding commercial AgGaS(2) by 1.5 times at 2.05 μm.
• The La compound exhibits type-I phase-matchable SHG behavior.
• Theoretical calculations suggest lattice vibrations play a role in the strong SHG effect.

Conclusions:

• The discovery of Ln(4)InSbS(9) expands the library of chiral nonlinear optical materials.
• The La member shows significant potential for applications requiring efficient and phase-matchable SHG.
• Lattice dynamics are identified as a key factor influencing the remarkable SHG performance.