Browsing by Subject "Central wavelength"

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Open Access
Burst-mode thulium all-fiber laser delivering femtosecond pulses at a 1 GHz intra-burst repetition rate
(Optical Society of America, 2017) Elahı, P.; Kalaycıoğlu, H.; Akçaalan, Ö.; Şenel, Ç.; Ilday, F. Ö.
We report on the development of, to the best of our knowledge, the first ultrafast burst-mode laser system operating at a central wavelength of approximately 2 μm, where water absorption and, consequently, the absorption of most biological tissue is very high. The laser comprises a harmonically mode-locked 1-GHz oscillator, which, in turn, seeds a fiber amplifier chain. The amplifier produces 500 ns long bursts containing 500 pulses with 1 GHz intra-burst and 50 kHz inter-burst repetition rates, respectively, at an average power of 1 W, corresponding to 40 nJ pulse and 20 μJ burst energies, respectively. The entire system is built in an all-fiber architecture and implements dispersion management such that output pulses are delivered directly from a single-mode fiber with a duration of 340 fs without requiring any external compression. This gigahertz-repetition-rate system is intended for ablation-cooled laser material removal in the 2 μm wavelength region, which is interesting for laser surgery due to the exceptionally high tissue absorption at this wavelength.
Open Access
Femtosecond laser written waveguides deep inside silicon
(Optical Society of America, 2017) Pavlov, I.; Tokel, O.; Pavlova, S.; Kadan, V.; Makey, G.; Turnalı, A.; Yavuz, Ö.; Ilday, F. Ö.
Photonic devices that can guide, transfer, or modulate light are highly desired in electronics and integrated silicon (Si) photonics. Here, we demonstrate for the first time, to the best of our knowledge, the creation of optical waveguides deep inside Si using femtosecond pulses at a central wavelength of 1.5 μm. To this end, we use 350 fs long, 2 μJ pulses with a repetition rate of 250 kHz from an Er-doped fiber laser, which we focused inside Si to create permanent modifications of the crystal. The position of the beam is accurately controlled with pump-probe imaging during fabrication. Waveguides that were 5.5 mm in length and 20 μm in diameter were created by scanning the focal position along the beam propagation axis. The fabricated waveguides were characterized with a continuous-wave laser operating at 1.5 μm. The refractive index change inside the waveguide was measured with optical shadowgraphy, yielding a value of 6 × 10−4, and by direct light coupling and far-field imaging, yielding a value of 3.5 × 10−4. The formation mechanism of the modification is discussed.