Light source with orthogonally linear polarized two-frequency beam from laser diode and its a

摘要

Abstract: A novel light source using a laser diode is proposed for the optical heterodyne interferometry. The light from this source has two frequency beams whose polarization directions are orthogonal. The light source consists of a laser diode and some optical elements. The laser diode is easy to give frequency modulation by the injection current modulation. Two- frequency waves are made by giving time difference due to a different optical path. A Mach- Zehnder interferometer using polarizing beam splitters and a right angle prism makes orthogonal linear polarized two-frequency light. In order to compensate the power fluctuation by injection current modulation and to keep the total power constant, an incoherent laser diode is added. This light source is suitable for practical application and can produce a small unit compared with a light source using a Zeeman laser or an acousto optic modulator. Three dimensional surface profilometry by a differential interferometer is demonstrated as its application.!6