High-quality monolayer graphene as large as 1.2×1.2 cm2 was synthesized by chemical vapor deposition and used as a transmitting saturable absorber for efficient passive mode-locking of a femtosecond bulk solid-state laser. The monolayer graphene mode-locked Cr:forsterite laser was tunable around 1.25 μm and delivered sub-100 fs pulses with output powers up to 230 mW. The nonlinear optical characteristics of the monolayer graphene saturable absorber and the mode-locked operation were then compared with the case of the bilayer graphene saturable absorber.
We
report on new acentric styryl quinolinium crystals with phenolic sulfonate
counteranions and investigate their supramolecular interactions that
affect their quadratic nonlinear optical properties. The phenolic
group acting as an electron-donor as well as hydrogen-bond donor site
is located at one end of the anion, while the sulfonate group acting
as an electron-acceptor as well as hydrogen-bond acceptor site is
located at the opposite end of the anion. New styryl quinolinium crystals
with 4-hydroxybenzenesulfonate and 6-hydroxynaphthalene-2-sulfonate
counteranions exhibit a large macroscopic optical nonlinearity with
very efficient second harmonic generation (SHG) efficiency. In styryl
quinolinium 4-hydroxybenzenesulfonate crystals, the styryl quinolinium
cation chromophores exhibit an acentric ordering with a high order
parameter close to 1.0, which is optimal for electro-optic applications
or THz-wave generation. The 4-hydroxybenzenesulfonate counteranions
form strong head-to-tail hydrogen bonds, and they are also packed
in acentric layers. The direction of the polar axes in cation and
anion layers is practically identical. Therefore, the introducing
phenolic group acting as an electron-donor as well as hydrogen-bond
donor to the sulfonate counteranion is a potential technique for crystal
engineering to tailor molecular ordering as well as the physical properties
of salt-type quinolinium derivatives.
Large-area monolayer graphene, synthesized by chemical vapor deposition, was transferred to a 1-in. quartz substrate. The high-quality monolayer graphene has been subject to characterization of the nonlinear properties near 1 μm and was successfully applied as saturable absorber for passive mode-locking of a femtosecond Yb:KLuW laser. The diode-pumped mode-locked Yb:KLuW laser was tunable around 1.04 μm and delivered pulses as short as 160 fs. The maximum output power of 160 mW was demonstrated for 203 fs pulse duration. The mode-locked laser results are comparable to those demonstrated with the same laser gain medium using single-walled carbon nanotubes as saturable absorbers.
We report Q-switched operation of a planar waveguide laser by evanescent-field interaction with single-walled carbon nanotubes deposited on top of the waveguide. The saturable-absorber-integrated gain medium, which operates based on evanescent-field interaction, enables the realization of a diode-pumped 2.5-cm-long Q-switched Yb:KYW waveguide laser emitting at 1030 nm. With such a compact cavity design, we achieve maximum output powers of up to 30 mW, corresponding to a single-pulse energy of 124 nJ, at 241 kHz repetition rate. The shortest pulse duration of 433 ns is generated at a repetition rate of 231 kHz.
Graphene has proved to be an excellent broadband saturable absorber for mode-locked operation of ultrafast lasers. However, for the mid-infrared (mid-IR) range where broadly tunable sources are in great needs, graphene-based broadly tunable ultrafast mid-IR lasers have not been demonstrated so far. Here, we report on passive mode-locking of a mid-IR Cr:ZnS laser by utilizing a transmission-type monolayer graphene saturable absorber and broad spectral tunability between 2120 nm and 2408 nm, which is the broadest tuning bandwidth ever reported for graphene mode-locked mid-IR solid-state lasers. The recovery time of the saturable absorber is measured to be ~2.4 ps by pump-probe technique at a wavelength of 2350 nm. Stably mode-locked Cr:ZnS laser delivers Fourier transform-limited 220-fs pulses with a pulse energy of up to 7.8 nJ.
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