Rapid, in-line, non-interferometric auto- and cross-correlator for microscopy

Area of Science:

• Optics and Photonics
• Microscopy
• Ultrafast Laser Science

Background:

• Accurate characterization of ultrafast laser pulse duration is critical for nonlinear optical microscopy.
• Existing methods for pulse duration measurement can be complex or require specialized optics expertise.
• In-situ measurement within the microscope's focal region is challenging but highly desirable.

Purpose of the Study:

• To develop a simple, in-line scheme for determining ultrafast pulse durations.
• To enable pulse characterization directly within the focal region of a high-numerical-aperture microscope objective.
• To facilitate rapid measurement for optimizing nonlinear optical microscopy applications.

Main Methods:

• Utilized photocurrent generated in a Gallium Arsenide Phosphide (GaAsP) photodiode.
• Employed two-photon absorption of orthogonally-polarized laser beams meeting at a slight angle.
• Implemented a non-interferometric autocorrelation scheme for laser pulse duration measurement.

Main Results:

• Successfully demonstrated a simple, in-line method for measuring ultrafast laser pulse durations (hundreds of femtoseconds).
• Validated the technique for both laser autocorrelation and cross-correlation between two lasers.
• The setup is readily buildable by users without advanced optics knowledge.

Conclusions:

• The developed method provides a rapid and accessible way to characterize ultrafast laser pulses in a microscope.
• This technique allows for the full utilization of laser intensity in nonlinear optical microscopy post-measurement.
• Simplifies pulse duration determination, making advanced microscopy techniques more accessible.