Browsing by Author "Baylam, I."
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Item Open Access Graphene mode-locked multipass-cavity femtosecond Cr4+:forsterite laser(Optical Society of America, 2013-04-19) Ozharar, S.; Baylam, I.; Cizmeciyan, M. N.; Balci, O.; Pince, E.; Kocabas, C.; Sennaroglu, A.We report, for the first time to our knowledge, the use of graphene as a saturable absorber in an energy-scaled femtosecond Cr4+: forsterite laser. By incorporating a multipass cavity, the repetition rate of the original short resonator was reduced to 4.51 MHz, which resulted in the generation of 100 fs, nearly transform-limited pulses at 1252 nm with a peak power of 53 kW. To the best of our knowledge, this is the highest peak power obtained from a room-temperature, femtosecond Cr4+: forsterite laser mode locked with a graphene saturable absorber. The corresponding pulse energy was 5.3 nJ with only 24 mW of average output power. The saturation fluence and modulation depth of the GSA were measured to be 25 mu J/cm(2) and 0.74%, respectively. The nonlinear effects in the Cr4+: forsterite medium that limit further power scaling were also investigated by using different output couplers. (c) 2013 Optical Society of AmericaItem Open Access Graphene supercapacitor as a voltage controlled saturable absorber for femtosecond pulse generation(OSA, 2014) Baylam, I.; Çizmeciyan, M. N.; Özharar, S.; Polat, Emre Ozan; Kocabaş, Coşkun; Sennaroğlu, A.For the first time to our knowledge, we employed a graphene supercapacitor as a voltage controlled saturable absorber at bias voltages of 0.5-1V to generate 84-fs pulses from a solid-state laser near 1255 nm.Item Open Access Graphene-gold supercapacitor as a voltage controlled saturable absorber for femtosecond pulse generation(Optical Society of America, 2016-02) Baylam, I.; Balci, O.; Kakenov, N.; Kocabas, C.; Sennaroglu, A.We report, for the first time to the best of our knowledge, use of a graphene-gold supercapacitor as a voltage controlled fast saturable absorber for femtosecond pulse generation. The unique design involving only one graphene electrode lowers the insertion loss of the device, in comparison with capacitor designs with two graphene electrodes. Furthermore, use of the high-dielectric electrolyte allows reversible, adjustable control of the absorption level up to the visible region with low bias voltages of only a few volts (0-2 V). The fast saturable absorber action of the graphene-gold supercapacitor was demonstrated inside a multipass-cavity Cr:forsterite laser to generate nearly transform-limited, sub-100 fs pulses at a pulse repetition rate of 4.51 MHz at 1.24 μm.Item Open Access Graphene-gold supercapacitor as a voltage-controlled saturable absorber for femtosecond pulse generation(OSA, 2015) Baylam, I.; Balcı, Osman; Kakenov, Nurbek; Kocabaş, Coşkun; Sennaroğlu, A.We report, for the first time to our knowledge, a voltage-controlled graphene-gold supercapacitor saturable absorber, as a modulator with adjustable insertion loss for low-gain mode-locked lasers. Nearly transform-limited, 80-fs pulses were generated near 1240 nm.Item Open Access Investigation of the ultrafast response and saturable absorption of voltage-controlled graphene(OSA, 2018) Baylam, I.; Çizmeciyan, M. N.; Kakenov, Nurbek; Kocabaş, Coşkun; Sennaroğlu, A.Ultrafast pump-probe measurements show that at a bias voltage of 1V, voltage reconfigurable graphene supercapacitors can operate as fast saturable absorbers with adjustable insertion loss over an ultrabroad spectral range from 630 to 1100 nm.Item Open Access Ultrafast spectroscopy of voltage reconfigurable graphene saturable absorbers in the visible and near infrared(IOP, 2019-04-23) Baylam, I.; Kakenov, Nurbek; Kocabaş, Coşkun; Sennaroğlu, A.; Çizmeciyan, M. N.We describe a detailed experimental investigation of the ultrafast nonlinear response of a voltagecontrolled graphene-gold saturable absorber (VCG-gold-SA) by employing femtosecond pump probe spectroscopy. Visible and near-infrared continuum probe pulses covering the spectral range from 500nm to 1600nm were used. In the experiments, the saturation fluence, modulation depth, ultrafast relaxation times, and the saturable absorption bandwidth of the VCG-gold-SA were measured as a function of the applied bias. We observed both saturable absorption and multi-photon absorption regimes as the applied bias voltage was varied between 0 and 2 V. Measurements indicate that under bias voltages in the range of 0–2 V, it should be possible to adjust the insertion loss of the VCG-gold-SA and at the same time, maintain a sufficient amount of modulation depth as well as an attainable level of saturation fluence over an ultrabroad spectral bandwidth. In particular, at the bias voltage of 1 V, the VCG-gold-SA exhibited fast saturable absorber behavior with adjustable insertion loss from 630nm to 1100nm. These results clearly demonstrate that the VCG-gold-SA can operate as a versatile mode locker for femtosecond pulse generation from lasers operating in the visible and near-infrared wavelengths.