Stimulated Raman scattering microscope with shot noise limited sensitivity using subharmonically synchronized laser...

Area of Science:

• Optics and Photonics
• Microscopy
• Biomedical Imaging

Background:

• Stimulated Raman scattering (SRS) microscopy offers label-free imaging capabilities.
• Traditional SRS microscopy often requires high-speed optical modulation for lock-in detection, which can introduce noise.
• Achieving low-noise detection is crucial for high-resolution and sensitive imaging applications.

Purpose of the Study:

• To propose and demonstrate a novel method for low-noise lock-in detection in SRS microscopy.
• To utilize subharmonically synchronized laser pulses to overcome limitations of high-speed modulation.
• To enable high-contrast, three-dimensional imaging of unlabeled biological samples.

Main Methods:

• Subharmonic synchronization of Yb-fiber laser pulses (38 MHz) to Ti:sapphire laser pulses (76 MHz) using a two-photon detector and an intra-cavity electro-optic modulator.
• Achieved synchronization with a timing jitter of less than 8 femtoseconds.
• Implemented high-frequency lock-in detection of the SRS signal without requiring high-speed optical modulation.

Main Results:

• Demonstrated successful synchronization of laser pulses with ultra-low jitter.
• The noise level of the lock-in signal was measured to be only 1.6 dB above the shot noise limit.
• Achieved high-contrast, three-dimensional imaging of unlabeled living cells.

Conclusions:

• Subharmonically synchronized laser pulses provide an effective approach for low-noise lock-in detection in SRS microscopy.
• This method simplifies the experimental setup by eliminating the need for high-speed optical modulation.
• The technique enables advanced label-free imaging of biological specimens with improved sensitivity and contrast.