Negative curvature fibre (NCF) guides light in its core by inhibiting the coupling of core and
cladding modes. In this work, an NCF was designed and fabricated to transmit ultrashort optical
pulses for multiphoton microscopy with low group velocity dispersion (GVD) at 800 nm. Its
attenuation was measured to be <0.3 dB.m-1
over the range 600-850 nm and the GVD was
-180±70 fs2
.m-1
at 800 nm. Using an average fibre output power of ~20 mW and pulse
repetition rate of 80 MHz, the NCF enabled pulses with a duration of <200 fs to be transmitted
through a length of 1.5 m of fibre over a tuning range of 180 nm without the need for dispersion
compensation. In a 4 m fibre, temporal and spectral pulse widths were maintained to within
10% of low power values up to the maximum fibre output power achievable with the laser
system used of 278 mW at 700 nm, 808 mW at 800 nm and 420 mW at 860 nm. When coupled
to a multiphoton microscope, it enabled imaging of ex vivo tissue using excitation wavelengths
from 740 nm to 860 nm without any need for adjustments to the set-up.