Tek duvarlı karbon nanotüp doyabilen soğurucuları ile kip kilitlenmiş Cr:LiSAF lazerinden 21 fs darbe üretimi

Single-walled carbon nanotube saturable absorbers (SWCNT-SAs) possess many favourable nonlinear optical properties over a wide range of wavelengths, such as strong absorption saturation, low non-saturable losses, short recovery times, and low-cost fabrication schemes. These properties have made SWCNT-SAs viable alternatives to semiconductor saturable absorber mirrors (SESAMs) for the mode locking of solid state and fiber lasers over a very broad wavelength range. In this thesis, the aim was to demonstrate the ultrashort pulse generating capability of SWCNT-SAs. First, the characterization of the SWCNT-SA used in the experiments was conducted. The absorption of the SWCNT-SA was measured to be around 2% at 850 nm, which is the free-running wavelength of Cr:LiSAF lasers. After performing pump-probe spectroscopy, the fast and slow decay times of the SWCNT-SA were measured to be 0.4 and 2.7 ps. The saturation fluence and the single pass modulation depth of the SWCNT-SA were further determined to be 45 μJ/cm2 and 0.3%, respectively. To test the ultrashort pulse generating capability of the SWCNT-SA, a Cr:LiSAF laser was chosen since it has a broad emission band, enabling the generation of ultrashort pulses with femtosecond duration. In the experiments, the Cr:LiSAF laser was pumped with 210 mW of pump power with two low-cost, low-power diode lasers at 660 nm, and produced around 9 mW of mode-locked output power centered around 875 nm. The pulse duration of 21 fs, which was achieved during the experiments, represents the shortest pulses directly generated from a SWCNT-SA mode-locked solid-state laser. The pulse repetition rate was 47.9 MHz with a pulse energy of 0.18 nJ and peak pulse power of 9 kW. The time-bandwidth product of the produced pulses was 0.56. Kerr lens mode locking iv experiments were further conducted to test if the SWCNT-SA puts any limitation on the obtainable pulse duration. The experiments clearly showed that the obtainable pulse duration was not limited by the SWCNT-SA. Furthermore, the continuous-wave operation of the Cr:LiSAF laser at 850 nm was experimentally investigated in detail. Accurate measurements of the transmissions of the output couplers used in the experiments were conducted. Then for the Cr:LiSAF laser constructed with different output couplers, the threshold pump power and power efficiency data were measured while the laser was tuned to operate exactly at 850 nm by using an intracavity tuning prism. The data taken enabled a complete experimental characterization of the continuous-wave Cr:LiSAF laser and provides useful guidelines for the construction of similar laser systems.