  A low voltage, wide bandwidth compact electro-optic modulator is a key
building block in the realization of tomorrow's communication and networking
needs. Recent advances in the fabrication and application of thin-film lithium
niobate, and its integration with photonic integrated circuits based in silicon
make it an ideal platform for such a device. In this work, a high-extinction
dual-output folded electro-optic Mach Zehnder modulator in the silicon nitride
and thin-film lithium niobate material system is presented. This modulator has
an interaction region length of 11 mm and a physical length of 7.8 mm. The
device demonstrates a fiber-to-fiber loss of roughly 12 dB using on-chip fiber
couplers and DC half wave voltage (V$\pi$) of less than 3.0 V, or a modulation
efficiency (V$\pi\cdot$L) of 3.3 V$\cdot$cm. The device shows a 3 dB bandwidth
of roughly 30 GHz. Notably, the device demonstrates a power extinction ratio
over 45 dB at each output port without the use of cascaded directional couplers
or additional control circuitry; roughly 31 times better than previously
reported devices. Paired with a balanced photo-diode receiver, this modulator
can be used in various photonic communication systems. Such a detecting scheme
is compatible with complex modulation formats such as differential phase shift
keying and differential quadrature phase shift keying, where a dual-output,
ultra-high extinction device is fundamentally paramount to low-noise operation
of the system.
