Controllable dual-pulse laser directly for nonlinear photoacoustic microscopy

Area of Science:

• Optics and Photonics
• Biomedical Imaging
• Laser Technology

Background:

• Nonlinear photoacoustic microscopy (PAM) typically necessitates dual-pulse laser excitation.
• Existing methods for generating dual-pulse laser trains are indirect, often relying on beam combination techniques.
• There is a need for compact and direct dual-pulse laser sources for advanced PAM applications.

Purpose of the Study:

• To report a novel, compact laser source capable of directly outputting controllable nanosecond dual pulses.
• To demonstrate the suitability of this laser source for nonlinear photoacoustic microscopy.
• To showcase enhanced imaging performance in Grüneisen-relaxation-based applications.

Main Methods:

• Development of a compact (∼5-cm-long cavity) laser source.
• Direct generation of controllable nanosecond (∼34 ns) dual pulses.
• Tunability of repetition rate (0–20 kHz), time delay (5–30 µs), and relative intensity ratio (20–500%).
• Achieved single pulse energy up to ∼95 µJ.

Main Results:

• The laser source directly outputs tunable dual pulses, meeting nonlinear imaging requirements.
• Demonstrated enhanced imaging contrast by 8 dB in typical Grüneisen-relaxation-based applications.
• The laser's performance is well-suited for nonlinear PAM, particularly for portable systems.

Conclusions:

• The developed compact dual-pulse laser source is a significant advancement for nonlinear photoacoustic microscopy.
• Its direct output and tunable parameters offer a versatile solution for various PAM applications.
• The enhanced imaging contrast highlights the potential for improved diagnostic capabilities, especially in portable settings.