Three-dimensional imaging of direct-written photonic structures

Area of Science:

• Photonics and Laser Technology
• Materials Science
• Optical Microscopy

Background:

• Femtosecond laser direct-write is a key technique for fabricating complex photonic structures.
• Analyzing the morphology of these 3D structures is crucial for device performance.
• Existing methods like linear microscopy and index profilometry have limitations in resolving fine details.

Purpose of the Study:

• To investigate the morphology of 3D photonic structures fabricated by femtosecond laser direct-write.
• To demonstrate the utility of third-harmonic generation microscopy for analyzing these structures.
• To assess the effectiveness of an adaptive-optical system in correcting aberrations for improved imaging.

Main Methods:

• Utilized third-harmonic generation (THG) microscopy.
• Investigated 3D waveguide arrays and waveguide-Bragg gratings in fused-silica and doped phosphate glass.
• Employed a sensorless adaptive-optical system to correct optical aberrations.
• Achieved a lateral resolution of less than 500 nm.

Main Results:

• Successfully analyzed the morphology of complex 3D photonic structures.
• Generated high-resolution volume reconstructions of the fabricated devices.
• Demonstrated the capability of THG microscopy to reveal details not visible with other techniques.
• Confirmed the effectiveness of the adaptive-optical system in aberration correction.

Conclusions:

• Third-harmonic generation microscopy is a powerful, nondestructive method for characterizing femtosecond laser-written photonic devices.
• The technique provides detailed 3D morphological information essential for understanding and optimizing photonic device performance.
• Adaptive optics significantly enhance the resolution and accuracy of THG microscopy for such applications.