Unveiling second harmonic generation from femtosecond-laser microstructured Nd:YAG crystal

Area of Science:

• Nonlinear optics
• Laser material processing
• Crystallography

Background:

• Neodymium-doped yttrium aluminum garnet (Nd:YAG) is a centrosymmetric crystal, where bulk second harmonic generation is theoretically forbidden.
• Femtosecond laser irradiation can induce micro-modifications in crystalline structures.
• Second harmonic microscopy (SHM) is a nonlinear optical imaging technique.

Purpose of the Study:

• To investigate the capability of SHM for analyzing laser-induced damage tracks in Nd:YAG crystals.
• To understand the nature of micro-modifications responsible for nonlinear signal generation.
• To explore the potential of SHM for fabricating novel photonic devices.

Main Methods:

• Application of second harmonic microscopy (SHM).
• Inscribing damage tracks using femtosecond laser irradiation.
• 2D and 3D imaging of modified Nd:YAG crystal structures.

Main Results:

• SHM successfully detected localized nonlinear signals in femtosecond laser-irradiated Nd:YAG.
• The induced micro-modifications in the crystal structure were responsible for the nonlinear signal generation.
• The study discussed the dependence of these modifications on irradiation and detection parameters.

Conclusions:

• SHM is a powerful tool for the morphological analysis of laser-written structures in Nd:YAG.
• Laser-induced structural modifications can lead to localized second harmonic generation in centrosymmetric materials.
• This research paves the way for designing and fabricating new nonlinear optical structures for photonic devices.