Compact ultrafast semiconductor disk laser: targeting GFP based nonlinear applications in living organisms

Area of Science:

• Biomedical Optics
• Laser Physics
• Microscopy

Background:

• Nonlinear microscopy offers high-resolution imaging capabilities.
• Portable and cost-effective laser sources are needed for widespread adoption of nonlinear microscopy.
• Semiconductor Disk Lasers (SDLs) are emerging as viable alternatives to traditional bulky laser systems.

Purpose of the Study:

• To present a portable, ultrafast Semiconductor Disk Laser (SDL) for nonlinear microscopy applications.
• To demonstrate the laser's capability for Two-Photon Excited Fluorescence (TPEF) and Second Harmonic Generation (SHG) imaging.
• To highlight the potential of this laser as a platform for portable nonlinear bio-imaging devices.

Main Methods:

• Modelocking an SDL using a quantum-dot semiconductor saturable absorber mirror (SESAM).
• Characterizing the laser output: 1.5 ps pulses, 500 MHz repetition rate, 965 nm central wavelength, 287 mW average power.
• Performing in vivo TPEF imaging of Caenorhabditis elegans (C. elegans) expressing Green Fluorescent Protein (GFP).
• Acquiring Second Harmonic Generation (SHG) images of C. elegans tissues.

Main Results:

• The SDL delivered 1.5 ps pulses at 500 MHz with 287 mW average power at 965 nm.
• Efficient TPEF imaging of C. elegans neuronal processes and cell bodies was achieved.
• The laser's wavelength optimally matched the two-photon action cross-section of GFP.
• Versatile SHG imaging of C. elegans pharynx, uterus, and body wall muscles was demonstrated.
• The potential to excite other commercial dyes was shown.

Conclusions:

• The developed portable SDL is suitable for nonlinear microscopy.
• The laser system enables efficient in vivo TPEF and SHG imaging of biological samples.
• This non-expensive, compact laser system can serve as a platform for developing portable nonlinear bio-imaging devices.