Khazaeinezhad, RezaHosseinzadeh Kassani, SaharPaulson, BjornJeong, HwanseongGwak, JiyoonRotermund, FabianYeom, Dong-IlOh, Kyunghwan2017-03-282017Khazaeinezhad, Reza, Sahar Hosseinzadeh Kassani, Bjorn Paulson, Hwanseong Jeong, Jiyoon Gwak, Fabian Rotermund, Dong-Il Yeom, and Kyunghwan Oh. 2017. “Ultrafast nonlinear optical properties of thin-solid DNA film and their application as a saturable absorber in femtosecond mode-locked fiber laser.” Scientific Reports 7 (1): 41480. doi:10.1038/srep41480. http://dx.doi.org/10.1038/srep41480.http://nrs.harvard.edu/urn-3:HUL.InstRepos:31731786A new extraordinary application of deoxyribonucleic acid (DNA) thin-solid-film was experimentally explored in the field of ultrafast nonlinear photonics. Optical transmission was investigated in both linear and nonlinear regimes for two types of DNA thin-solid-films made from DNA in aqueous solution and DNA-cetyltrimethylammonium chloride (CTMA) in an organic solvent. Z-scan measurements revealed a high third-order nonlinearity with n2 exceeding 10−9 at a wavelength of 1570 nm, for a nonlinarity about five orders of magnitude larger than that of silica. We also demonstrated ultrafast saturable absorption (SA) with a modulation depth of 0.43%. DNA thin solid films were successfully deposited on a side-polished optical fiber, providing an efficient evanescent wave interaction. We built an organic-inorganic hybrid all-fiber ring laser using DNA film as an ultrafast SA and using Erbium-doped fiber as an efficient optical gain medium. Stable transform-limited femtosecond soliton pulses were generated with full width half maxima of 417 fs for DNA and 323 fs for DNA-CTMA thin-solid-film SAs. The average output power was 4.20 mW for DNA and 5.46 mW for DNA-CTMA. Detailed conditions for DNA solid film preparation, dispersion control in the laser cavity and subsequent characteristics of soliton pulses are discussed, to confirm unique nonlinear optical applications of DNA thin-solid-film.en-USJournal Article2017-03-2810.1038/srep41480