5 MHz beat frequency He-Ne laser equipped with bireflectance cavity mirror

A 5 MHz beat frequency He-Ne laser equipped with bireflectance (double-reflection) cavity mirror is described. It is realized on the principle that the reflecting phase jumps are different along the fast and slow axes when the incident light is oriented in a direction perpendicular to the bireflectance cavity mirror. By using the transverse Zeeman effect for reducing the mode coupling, the laser can produce two orthogonal linear polarization components with 5 MHz beat frequency. The direction of the magnetic field and the polarization property of the laser are tested. After the frequency is stabilized, the laser is calibrated with the iodine frequency stabilization laser (the wavelength uncertainty is 2.5 ×10-11 of the National Institute of Metrology (NI) of China, and the results show that the frequency stabilization is 1.4×10-10 (sampled in 10 s), the wavelength uncertainty is 3×10-8. The laser has such merits as simple form, favorable orthogonal property and appropriate beat frequency. Such a dual-frequency laser is very suitable for manufacturing high-speed heterodyne interferometers.