Abstract
The characterisation of dual-output Mach-Zehnder interferometers operating
with long-range surface plasmon-polaritons at a free-space wavelength of
$\sim$
1370 nm is
reported. The devices were constructed by embedding Au stripes in Cytop claddings,
and consist of a symmetric Mach-Zehnder interferometer in cascade with a 50:50
coupler. By injecting electric current via probes to generate heat in the
active region in one arm of the interferometer, a phase difference between
the arms was thermo-optically induced, modulating the optical power of the
two outputs. The outputs were complementary as expected theoretically, thus
demonstrating the switching abilities of the structure. The advantages for
sensing applications of a dual-output interferometer over a single-output
one are a 2X larger dynamic range and the ability to cancel common noise and
source fluctuations. The larger dynamic range and noise cancellation produced
a minimum detectable phase shift 4X lower than obtained by monitoring a single
output. The smallest value of
$\Delta\phi_{\min}$
obtained was
$\sim$
3 mrad. The structure is especially promising for (bio)chemical
sensing applications.
© 2013 IEEE
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