title: Femtosecond pulse generation from a Ti3+:sapphire laser near 800  nm with voltage reconfigurable graphene saturable absorbers.
abstract: We experimentally show that a voltage-controlled graphene-gold supercapacitor saturable absorber (VCG-gold-SA) can be operated as a fast saturable absorber with adjustable linear absorption at wavelengths as low as 795 nm. This was made possible by the use of a novel supercapacitor architecture, consisting of a high-dielectric electrolyte sandwiched between a graphene and a gold electrode. The high-dielectric electrolyte allowed continuous, reversible adjustment of the Fermi level and, hence, the optical loss of the VCG-gold-SA up to the visible wavelengths at low bias voltages of the order of a few volts (0-2 V). The fast saturable absorber action of the VCG-gold-SA and the bias-dependent reduction of its loss were successfully demonstrated inside a femtosecond Ti3+:sapphire laser operating near 800 nm. Dispersion compensation was employed by using dispersion control mirrors and a prism pair. At a bias voltage of 1.2 V, the laser operated with improved power performance in comparison with that at zero bias, and the VCG-gold-SA initiated the generation of nearly transform-limited pulses as short as 48 fs at a pulse repetition rate of 131.7 MHz near 830 nm. To the best of our knowledge, this represents the shortest wavelength where a VCG-gold-SA has been employed as a mode locker with adjustable loss.
authors.forename: Isınsu
authors.initials: I
authors.lastname: Baylam
authors.forename: Sarper
authors.initials: S
authors.lastname: Ozharar
authors.forename: Nurbek
authors.initials: N
authors.lastname: Kakenov
authors.forename: Coskun
authors.initials: C
authors.lastname: Kocabas
authors.forename: Alphan
authors.initials: A
authors.lastname: Sennaroglu