Compact Tunable Resonance Filters with Ultra-Broad Rejection for Silicon
Photonics
Abstract
This paper reports a novel design of compact tuneable resonance filter
with a highly extinguished and ultra-broad out-of-band rejection in CMOS
compatible silicon photonics technology platform. The proposed device is
designed with two identically apodized distributed grating structures
for guided Fabry-Pérot resonant transmissions in a silicon on insulator
rib waveguide structure. The device design parameters are optimized by
theoretical simulation for a low insertion loss singly-resonant
transmission peak at a desired wavelength. Â However, the devices were
fabricated (using in-house facilities) to demonstrate multiple resonant
transmission peaks along with a singly-resonant one. Â We observed that
a device length of as low as ∼35 �m exhibits a rejection band as
large as ∼60 nm with an extinction of ∼40 dB with respect to the
resonant wavelength peak at ��∼1550 nm (FWHM ∼80 pm, IL∼2
dB). The experimental results have been shown to be closely matching to
our theoretical simulation and modelling results. As expected from the
theoretical prediction, the trend pertaining to the trade-off between
passive insertion loss and Q-value of the resonances has been observed
depending on the device parameters. The thermo-optic tuning
characteristics of resonant wavelengths have been obtained by
integrating microheaters in the cavity. The resonance peak has been
tuned at a rate of 96 pm per mW of consumed thermal power. The
thermo-optic switching response has been measured to be in the order of
~5 �s. As a potential application, noise associated
with an amplified pump wavelength (��∼1550 nm) has been shown to
be suppressed by ∼15 dB (up to the detector noise floor) which can be
investigated further for large-scale integrated quantum photonic
circuits. The demonstrated device can also be explored further for many
other applications such as modulation, add-drop multiplexing, sensing
etc.Â