EFFICIENT LINBO3 BALANCED BRIDGE MODULATOR-SWITCH WITH AN ION-ETCHED SLOT

A simple modified balanced bridge modulator or switch is reported. The modulator is comprised of only straight waveguides and an ion-etched slot used for a conventional phase shifter. The slot excavated at the center of two coupled waveguides solves the coupling of them. 3-dB coupler monitoring is performed here by a metal loading. The modulator is fabricated by diffusing Ti into z-cut LiNbO3. Each patterned waveguide is fabricated by diffusing Ti into z-cut LiNbO3. Each patterned waveguide is 7 μm wide and the spacing is 7 μm. The 3-dB coupler is 2.9 mm long, and the excavated slot is 15 mm long, 4 μm wide, and 4.5 μm deep. The overall length is 20.8 mm. For the TM-like fundamental mode, the half-wave voltage was 2.8 V, the extinction ratio was -15 dB, and the optical insertion loss was as low as 2.6 dB at the 1.15-μm wavelength.