Phase modulator and optical modulation device

An optical modulator includes an input unit , a splitter unit , a first waveguide , a second waveguide , a directional coupler unit , a first output unit , a second output unit , a first liquid-crystal cell , and a second liquid-crystal cell . The splitter unit , the first waveguide , the second waveguide , and the directional coupler unit form an optical interferometer that branches an input light and causes the branched lights to interfere. The first liquid-crystal cell and the second liquid-crystal cell transmit the lights branched in the optical interferometer and delay the lights according to applied signals, respectively. The second liquid-crystal cell is thinner than the first liquid-crystal cell