Two-photon microscopy and the $100,000 question: tunable or fixed-wavelength femtosecond laser?

Two-photon microscopy, a fluorescence-imaging technique used by many researchers in the life sciences, has over time become a mature application. The single most expensive piece of equipment in two-photon microscopy setups is the femtosecond laser--a technology that most biologists are unfamiliar with. The most common type used is the titanium sapphire (Ti:sapphire) tunable laser, which can cost up to $200,000; however, cheaper and smaller fixed-wavelength fiber lasers have become available that can deliver similar results.