3-Photon-Microscopy has recently become a popular technique, especially for deep-tissue imaging to study Neuroscience. But it is still missing a cost-effective and useful solution for ultrafast laser sources generating femtosecond pulses in the biological transmission windows which are suffering less from optical attenuation, i.e. 1.3 μm and 1.7 μm. The two available solutions are femtosecond lasers with NOPA (noncolinear optical parametric amplifier) as a tunable but expensive light source and more affordable femtosecond lasers with just one fixed wavelength, which is less convenient for the imaging facilities.
Fig. 1 Typical HGM imaging in epidermis and upper dermis of human skin showing (a) stratum corneum and stratum granulosum, (b) stratum spinosum, and (c) dermal papilla consisting of basal cells and collagen fiber. Contrast agents are demonstrated in pseudo-color. THG: cyan hot, SHG: red hot. Scale bar: 50 μm.
The new femtosecond light source SOPRANO of Cycle GmbH is a fiber-laser-based solution with up to three-color outputs simultaneously, which is also wavelength tunable. Now the users can not only use this versatile light source as the optimal engine for 3-Photon-Microscopy but also for several other multiphoton imaging techniques (e.g. THG, SHG and 2-Photon-Imaging).
Initial versions of the SOPRANO laser have been developed together with the Center for Free-Electron Laser Science at DESY and University of Hamburg, which have several collaborations with medical institutes in northern Germany. One prototype of this laser was used for HGM (Harmonic Generation Microscopy), which is one of the most important label-free techniques in skin biopsy. Figure 1 shows example images taken from human skin tissue visualized by SHG/THG (Second-/Third-Harmonic Generation).
Cycle’s groundbreaking laser has a fixed (or optional tunable) repetition rate between 1 MHz and 30 MHz. It has up to 3 output ports, which have either a tunable wavelength around 1300 nm, 1550 nm, or 1700 nm with 500-mW average power each. The pulse duration is well below 100 fs, depending on the chosen wavelength. Available is also an optional dispersion pre-compensation unit to have the shortest pulses possible at the sample after all microscope optics as well as a frequency conversion unit for lower wavelength.
Cycle GmbH will exhibit at Photonics West in San Francisco, California from February 5th to 7th, 2019. Visit Cycle’s booth no. 3406 to see Cycle’s patented TCBOC, which can precisely synchronize two ultrafast lasers together with a timing jitter as low as 1 fs RMS over 8 hours. The patented BOMPD which locks an ultrafast laser tightly to a RF source (or vice versa) with similar timing jitter performance is also on display.