Mid-infrared (2.75-6.0-microm) second-harmonic generation in LiInS(2)

Area of Science:

• Nonlinear Optics
• Solid-State Physics
• Materials Science

Background:

• Phase-matched second-harmonic generation (SHG) is crucial for frequency conversion in lasers and optical parametric devices.
• Lithium Indium Sulfide (LiInS2) is a promising nonlinear optical material, but its performance characteristics require detailed investigation.
• Accurate phase-matching data and understanding optical damage thresholds are essential for practical applications of nonlinear crystals.

Purpose of the Study:

• To investigate phase-matched second-harmonic generation (SHG) in LiInS2 crystals.
• To evaluate the performance of LiInS2 for mid-infrared (mid-IR) nonlinear optical applications.
• To determine the optical damage threshold of LiInS2 crystals at specific wavelengths.

Main Methods:

• Utilized the tunable picosecond output of the free-electron laser for infrared experiments (FELIX) as a pump source.
• Pumped LiInS2 crystals in the mid-IR range (2.75–6.0 micrometers) to achieve second-harmonic generation.
• Measured the optical damage threshold of the crystals at a 5-micrometer wavelength.

Main Results:

• Successfully obtained phase-matched second-harmonic generation in LiInS2 crystals.
• Observed deviations from the theoretically calculated phase-matching curve based on existing refractive-index data.
• Determined an optical damage threshold of 1.1 J/cm² (>6 GW/cm²) at 5 micrometers.

Conclusions:

• LiInS2 crystals exhibit efficient phase-matched SHG in the mid-IR range.
• The experimental results suggest a need for refined refractive-index data for LiInS2 for precise phase-matching predictions.
• LiInS2 demonstrates significant potential for parametric interactions spanning the 1–13 micrometer wavelength range.