Single-scan interferometric second harmonic generation microscopy using a kHz phase-scanner.

Area of Science:

• Nonlinear Optics
• Microscopy Techniques
• Materials Science

Background:

• Conventional laser-scanning microscopy acquires signals pixel by pixel, leading to lengthy acquisition times.
• Interferometric Second Harmonic Generation (I-SHG) provides valuable phase information for characterizing sample polarity but is often time-consuming.
• Existing I-SHG methods require multiple frames for phase-shifting, limiting their application in dynamic studies.

Purpose of the Study:

• To significantly reduce the acquisition time for Interferometric Second Harmonic Generation (I-SHG) imaging.
• To develop a method for characterizing the relative polarity of various samples more efficiently.
• To enable I-SHG measurements at the time-scale of seconds, comparable to standard intensity imaging.

Main Methods:

• Implemented phase scanning within each pixel during sample scanning using an electro-optic phase-scanner.
• Developed a single-scan I-SHG (1S-ISHG) technique allowing parallel retrieval of phase and amplitude information.
• Explored slower modulations for enhanced phase measurement precision without spatial or temporal shifts.

Main Results:

• Achieved over an order of magnitude reduction in I-SHG acquisition time.
• Demonstrated that 1S-ISHG requires exposure times comparable to standard Second Harmonic Generation (SHG) intensity images.
• Showcased the ability to retrieve phase information in parallel with amplitude at the second time-scale.

Conclusions:

• The developed 1S-ISHG technique significantly accelerates I-SHG measurements, making it suitable for dynamic processes.
• This method extends the applicability of I-SHG to large-scale studies and samples with low signal-to-noise ratios.
• 1S-ISHG offers a powerful, time-efficient approach for characterizing sample polarity using nonlinear optical microscopy.