We report on a flexible multiphoton imaging system, suitable for simultaneous and efficient excitation of red (DsRed), yellow (YFP), green (GFP) and blue (DAPI) fluorophores. We used a simple, compact laser system, consisting of a 1 μm high energy diode-pumped oscillator and a tunable wavelength extension using a photonics crystal fibre. The combination of a near IR excitation wavelength, high energy per pulse for efficient three photon excitation and spectral extension for GFP excitation allows for high flexibility.We present experimental results of simultaneous and efficient
imaging fluorophores couples from the UV to the red (DAPI-RFP, GFP-RFP).
A low density medium like a gas is attractive for laser amplification due to its high breakdown threshold and scalability to very large volumes. Moreover, the non-linear index of refraction of a gas is of three orders of magnitude lower than for a solid medium that is particularly suitable for direct amplification, without pulse stretching, of high-power ultrashort pulses. Among all gas laser media, application of the photolytical XeF(C-A) laser for high energy amplification is very attractive for the development of ultra-high power laser systems up to the petawatt power level due to the XeF(C-A) broad amplification bandwidth (80 nm FWHM centered near 475 nm) and a rather high saturation fluence (~0.05 J.cm<sup>-2</sup>), as well as a very low level of Amplified Spontaneous Emission. The paper presents the strategy of the LP3 laboratory to develop a high-contrast multiterawatt femtosecond laser chain based on a hybrid (solid/gas) technology, including a Ti:Sapphire oscillator generating 50 fs pulses at 950 nm, an Optical Parametric Chirped Pulse Amplification stage, a frequency converter, and a final high-energy amplification in the photolytical XeF(C-A) amplifier. Our approach is supported by first pilot experiments of femtosecond pulse amplification in a compact photolytical XeF(C-A) amplifier.