Photorefractive Volume Gratings Stabilize Wavelengths

A research team from the National Research Laboratory of Metrology in Tsukuba, Japan, has stabilized the wavelengths of two diode lasers by using two photorefractive volume gratings in one lithium niobate (LiNbO₃) crystal. Both wavelengths exhibited good short- and long-term stability, and the photorefractive crystal allowed effective control of the separation of the wavelengths.
Diode lasers with stable wavelengths are a must for applications in high-resolution spectroscopy.
There are several methods for locking the diode laser frequency at an atomic absorption line, including using volume holography in LiNbO₃. However, these methods can stabilize only a single wavelength, and the measurement range is limited.