Reflection-type optical device

A reflection-type optical device comprising:

• a first polarization separation/combination part for separating a light beam incident from a first port into a first light beam having an ordinary ray component and a second light beam having an extraordinary ray component and emitting them;
• a first Faraday rotating part for rotating a polarization direction of the first light beam by 45° and emitting it as a third light beam;
• a second Faraday rotating part for rotating a polarization direction of the second light beam by −45° and emitting it as a fourth light beam having a polarization direction substantially parallel to a polarization direction of the third light beam;
• a polarizer which allows the third and the fourth light beams to pass through;
• a reflecting part for reflecting the third and the fourth light beams;
• and
• a second polarization separation/combination part which allows the third light beam, which has been reflected by the reflecting part and has passed through the polarizer and a third Faraday rotating part, to pass through as an extraordinary ray, allows the fourth light beam, which has been reflected by the reflecting part and has passed through the polarizer and a fourth Faraday rotating part, to pass through as an ordinary ray, combines the third and the fourth light beams, and emits them from a second port.