FLIM imaging of auto-fluorescent NAD(P)H and FAD to track metabolic changes of non-adherent leukemia cells using microfluidic trapping array

Self-sweeping of laser frequency is relatively new effect in fiber lasers. The effect consists in periodic dynamics of the laser frequency without use of tuning elements and electrical drivers for frequency tuning. Owing to broad sweeping range (up to 23 nm) and simplicity, self-sweeping fiber lasers are attractive sources for applications demanding tunable radiation. Currently the self-sweeping effect in fiber lasers was observed in different spectral regions covering range from 1 to 2.1 μm. However, it is difficult to control spectral dynamics due to self-induced nature of the sweeping effect. In the paper, we demonstrated linearly-polarized Tm-doped fiber laser with lasing near 1.9 μm with manually controlled the spectral dynamics with pump power adjustment. The laser operates in three self-sweeping regimes depending on pump power: 1) with normal scanning direction at high rate (~5 nm/sec) and, 2) with reverse one at low sweeping rate (~0.1 nm/sec) and 3) wavelength stopping. In the case of wavelength stopping, the wavelength can be stopped at arbitrary value in the range from 1912 to 1923 nm depending on prehistory of spectral dynamics of the laser. The wavelength stability in case of wavelength stopping is better than 50 pm within 5 minutes. In the case of linear scanning of laser line, sweeping range exceeds 15 nm.