MAGNETIC FIELD SENSOR

PURPOSE:To miniaturize the title sensor by shortening the length of a crystal, by forming a Faraday rotary element from a crystal body wherein Mn is added to a CdTe crystal body in the magnetic sensor utilizing Faraday effect. CONSTITUTION:The incident light from an optical fiber 1 passes through a rod lens 2 and a polarizer 3 to be incident on a rectangular parallelepiped- shaped Faraday rotary element 4. Herein, a plane of polarization is rotated by an angle theta by a magnetic field 5 and the emitted light is incident on a detector 6 to replace rotation with the intensity of light and guided to an LED through a rod lens 7 and an optical fiber 8 to measure a magnetic field. The element 4 is formed from a CdMnTe crystal body wherein a very small amount of Mn is added to a CdTe crystal body. This crystal body has an extremely large Verdet constant and, therefore, the length of a crystal can be shortened in order to obtain the same sensitivity. By this method, a sensor is miniaturized to make it possible to measure magnesium in a narrow place.