Variable lens and birefringence compensator for continuous operation

Abstract

Apparatus and method are disclosed for providing an improved variable lens and birefringence compensator envisioned for use within the resonator cavity of a laser which is capable of continuous operation. A pair of cylindrical bodies of optical material (12A, B) having a temperature dependent index of refraction are thermally coupled to heat exchange means (14A, B) surrounded by potting material (16) which adds heat to or extracts heat from the exterior surfaces of the cylindrical bodies in order to establish radially dependent thermal and stress gradients within the bodies. The heat exchange means (14A, B) is supplied power through leads (20A, B) and infuses or removes heat in order to establish a thermal gradient which is used to create a dynamic lens of opposite power to that of the laser rod which corrects beam divergence in the lased output. The stress gradient causes the compensator body to behave like a birefringent substance. The double refracting behavior of the compensator effectively reconstructs the laser beam passing through it which was depolarized by the birefringent action of the laser rod itself. The tandem arrangement (48) of variable lens and birefringence compensators is coordinated by temperature sensor and trigger means (66, 68) which sense the temperature of the compensators (50, 52) through thermocouples (60, 61) and which are coupled to heat exchange means (14A, B) via control means (70, 72) and leads (20A, 20B). The control means (70, 72) prevent the compensators from overheating and enable the lensing and compensating action to be maintained without interruption.