  We present a photonics integrated circuit on silicon substrate
withreconfigurable nonreciprocal transmission that exhibits a large
isolationratio and low insertion loss. It also offers ability for all-optical
function-alities, like optical computing gates, or a flip-flop. The circuit is
a mixedcavity system of which the linear transmission can be tuned as a
Fanoresonance or electromagnetically induced transparency (EIT) using
twointegrated heaters. With high optical intensity inside the cavity, the
Fanoresonance and EIT peak induce a strong distortion due to thermal
non-linearities in the cavity, and these distortions depend on the
transmissiondirection due to the asymmetric power distribution in the cavities.
Theresulting large isolation ratio is attributed to the inherent sharp slope
ofthe Fano resonance and the large extinction ratio of the EIT peak. Thus,a
high-power forward-propagating signal will trigger the nonreciprocalphenomenon
for low-loss transmission, while backward transmission willsee high loss
irrespective of its power level, which is an outstanding im-provement upon
previously reported nonlinearity induced nonreciprocityin silicon photonics.
The reconfigurability of the high transmission direc-tion comes from the
efficient control of the mode excitation and couplinginside the cavity using
the integrated heaters. Also, by using a separatepump laser, the device could
be developed for all-optical functions likeswitching, logic and computing.
