Electro-Absorber/Modulator Recovery Time for High Energy Pulse Burst Monolithic Mode-Locked Tapered Laser

The enabler for tapered mode-locked (ML) semiconductor laser to become an alternative to Ti:S laser in two- photon excitation fluorescence lifetime (2ph-FLIM) measurements is the ability to produce hundred pJ energy pulses with picosecond duration. Monolithic ML lasers with that high pulse energy were pioneered by CSEM and III-V lab [1] and later were also demonstrated by FBH [2]. However, the pulse repetition rate remains too high (3–6 GHz) to allow one for the fluorescence decay time measurements between the excitation pulses in majority of popular dyes (lifetime 1–10 ns). In HiLight project [3], we introduce a built-in intracavity modulator (inset in Fig. 1(a)) to produce a burst of mode-locked pulses at 900 nm wavelength to pump fluorescent dyes in two-photon excitation regime. The fluorophore lifetime is imprinted in both the growing fluoresce emission during the pulse burst and its decay after the burst, thus allowing the SNR to be improved in a single-burst 2ph-FLIM.