Broadband phase modulator based on a multimode channel waveguide in thin-film lithium niobate

Experimental samples of integrated optical microwave modulators on thin-film lithium niobate were developed and fabricated. An approach was chosen in which optical waveguide was fabricated with larger width than required for its single-mode operation and arising high-order modes were suppressed with help of modulator electrodes placed close to the waveguide. Characteristics of the fabricated samples were measured, the correspondence between results of direct electrooptic bandwidth measurement and its theoretical estimate based on $S$-parameters measurement was demonstrated. Effective microwave modulation of optical radiation within the bandwidth of more than 30 GHz at $U_\pi L$ parameter value of 4 V $\cdot$ cm was demonstrated.