Phase modulator and optical device

A phase modulator comprising;

• a first liquid crystal element in which a first liquid crystal material is filled between a pair of substrates facing each other, and a second liquid crystal element in which a second liquid crystal material is filled between a pair of substrates facing each other, wherein:
• the first liquid crystal element and the second liquid crystal element are arranged so that a light passes through the first liquid crystal element and the second liquid crystal element;
• in the state in which no voltage is applied between the pair of substrates of the first liquid crystal element nor between the pair of substrates of the second liquid crystal element, the first liquid crystal material shows optical isotropy with a first isotropy refractive index and the second liquid crystal material shows optical isotropy with a second isotropy refractive index;
• and
• in the state in which a predetermined range of voltage is applied both between the pair of substrates of the first liquid crystal element and between the pair of substrates of the second liquid crystal element, the first liquid crystal material shows optically uniaxial anisotropy with a first ordinary refractive index and a first extraordinary refractive index which is larger than the first ordinary refractive index, and the second liquid crystal material shows optically uniaxial anisotropy with a second ordinary refractive index and a second extraordinary refractive index which is smaller than the second ordinary refractive index.