Improving third harmonic generation performance by elevating the operation temperature of KDP and DKDP crystals.

Area of Science:

• Nonlinear optics
• Laser science and technology
• Materials science

Background:

• Potassium dihydrogen phosphate (KH₂PO₄, KDP) family crystals are essential nonlinear optical materials for inertial confinement fusion (ICF) laser drivers.
• Third harmonic generation (THG) using KDP and DKDP crystals is a critical UV generation scheme in ICF.
• Improving output energy, conversion efficiency, and anti-damage ability of these crystals is a key research focus.

Purpose of the Study:

• To investigate the effect of elevated operating temperatures on the THG performance of KDP and DKDP crystals.
• To determine if increasing crystal temperature can enhance UV frequency conversion efficiency and laser-induced damage threshold (LIDT).

Main Methods:

• Experimental analysis of THG performance of KDP and DKDP crystals at elevated temperatures (up to 130 °C).
• Variable-temperature Z-scan tests to probe optical properties.
• Measurement of THG energy, conversion efficiency, and LIDT.

Main Results:

• At 130 °C, THG energy increased by 11.9%-16.5% for KDP and 4.2%-7.6% for DKDP.
• Conversion efficiency increased by 5.3%-5.4% for KDP and 4.2%-6.6% for DKDP.
• LIDT increased by 17.1%-24.5% for KDP and 14.2%-26.5% for DKDP.
• Variable-temperature Z-scan tests showed suppressed two-photon absorption at higher temperatures.

Conclusions:

• Substantially elevating the operating temperature of KDP and DKDP crystals is an effective strategy to improve THG performance.
• Higher temperatures suppress two-photon absorption, leading to enhanced UV frequency conversion and increased LIDT.
• This research provides a valuable technique for developing advanced UV and deep-UV lasers for ICF facilities.