A PHASE-CONJUGATE TWYMAN-GREEN INTERFEROMETER WITH INCREASED SENSITIVITY FOR LASER-BEAM COLLIMATION

A Twyman-Green interferometer having a phase-conjugate mirror in one a rm and double mirror in another arm is described to measure divergence and to check the collimation of a laser beam. It uses an internally s elf-pumped phase conjugation in BaTiO3 crystal as phase-conjugate mirr or. The use of double mirror gives a dual interference field which res ults in improved sensitivity in collimation testing. The dual-field in terferogram is also useful in easily distinguishing between the diverg ent and convergent nature of the test beam. Measurement results are pr esented.