LASER LONGITUDINAL MODE SPLITTING PHENOMENON AND ITS APPLICATIONS IN LASER PHYSICS AND ACTIVE METROLOGY SENSORS

This paper is a summary of laser mode splitting and its applications. When a quartz crystal is placed in the laser cavity, every mode of the laser will be split into two orthogonally polarized components. The m agnitude of the split is decided by the thickness of the quartz crysta l plate and the angle between the crystalline axis and the beam. Simil arly, when a KDP crystal is placed in the cavity and the voltage appl ied to the crystal is adjusted, or an optical element to which a force is applied, the modes are split linearly. According to the results of the theory and experiments, several applications of the laser mode sp lit to laser physics and metrology are described. These applications a re: study of mode competition (Section 5.2), study of abnormal dispers ion (Section 5.3), designing birefringence dual frequency lasers (Sect ion 4), observing mode competition (Section 5.1) and effect of abnorma l dispersion on mode splitting (Section 5.2), and measuring angles (Se ction 6.1), displacement (Section 6.2), nanometre displacement (Sectio n 6.3), force and weight (Section 6.4). The main error and common matt ers (sensitivity, measurement range, etc.) are discussed in Sections 6 .5 and 6.6.