Femtosecond Er-doped fiber laser source tunable from 872 to 1075 nm for two-photon vision studies in humans

• Published in: Biomedical optics express Vol. 13; no. 4; pp. 1899 - 1911
• Main Authors: Stachowiak, Dorota, Marzejon, Marcin, Bogusławski, Jakub, Łaszczych, Zbigniew, Komar, Katarzyna, Wojtkowski, Maciej, Soboń, Grzegorz
• Format: Journal Article
• Language: English
• Published: United States Optica Publishing Group 01.04.2022
• ISSN: 2156-7085; 2156-7085
• DOI: 10.1364/BOE.452609

We report the development of a widely-tunable femtosecond fiber laser system and its application for two-photon vision studies. The source is based on an Er-doped fiber laser with spectral shift up to 2150 nm, followed by a second harmonic generation module to generate a frequency-doubled beam tunable from 872 to 1075 nm. The source delivers sub-230 fs pulses with nearly-constant duration over the entire tuning range, with output powers between 0.68–1.24 mW, which corresponds to a pulse energy of 13.2–24.1 pJ. Such pulse energy is sufficient for employing a system for measurements of two-photon scotopic spectral sensitivity of two-photon vision in humans. The laser parameters allow for very efficient and safe two-photon stimulation of the human visual system, as proved by a good separation between one- and two-photon thresholds for wavelengths below 950 nm, which we have confirmed for 3 healthy subjects.