Materials
with electrically tunable optical properties offer a
wide range of opportunities for photonic applications. The optical
properties of the single-walled carbon nanotubes (SWCNTs) can be significantly
altered in the near-infrared region by means of electrochemical doping.
The states’ filling, which is responsible for the optical absorption
suppression under doping, also alters the nonlinear optical response
of the material. Here, for the first time we report that the electrochemical
doping can tailor the nonlinear optical absorption of SWCNT films
and demonstrate its application to control pulsed fiber laser generation.
With a pump–probe technique, we show that under an applied
voltage below 2 V the photobleaching of the material can be gradually
reduced and even turned to photoinduced absorption. Furthermore, we
integrated a carbon nanotube electrochemical cell on a side-polished
fiber to tune the absorption saturation and implemented it into the
fully polarization-maintaining fiber laser. We show that the pulse
generation regime can be reversibly switched between femtosecond mode-locking
and microsecond Q-switching using different gate voltages. This approach
paves the road toward carbon nanotube optical devices with tunable
nonlinearity.
We demonstrate, to the best of our knowledge, the first bismuth-doped fiber laser operating at 1.7 μm mode-locked by means of Kerr nonlinearity. The laser setup has a figure-of-eight all-fiber design with a nonlinear amplifying loop mirror (NALM) and yields 17 ps pulses with a 3.57 MHz repetition rate and the energy 84 pJ. Using the master oscillator power amplifier scheme with a bismuth fiber amplifier, the output pulse energy of 5.7 nJ was achieved. Further pulse compression in the fiber compressor shortened pulses to 630 fs. The operation of the master oscillator was modeled using the nonlinear Schrödinger equation. Calculated data are in good agreement with experimental results.
Bi-and Er-codoped germanosilicate optical fibers have been fabricated and studied as a potential gain medium for fiber-based devices operating in the near infrared region. A broadband optical amplifier operating in the wavelength range from 1515 to 1775 nm has been realized using the developed bismuth-and erbium-codoped fibers. The 15 dB small-signal gain band covers 260 nm when pumped by a laser diode at 1460 nm with an output power of 350 mW.
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