Beam Pointing Detection by Interference with a Frequency-Shifted Higher-Order Mode

The detection and stabilization of laser beam pointing is of great interest for multiple high precision applications, e.g., interferometric measurements [1]. Beside the typically applied beam pointing detection based on quadrant photodiodes [2] an alternative detection method based on the superposition of the deflected beam with a higher order mode has been demonstrated [3]. However, in the so far presented approach the beam pointing detection was realized by the superposition of two modes at the same frequency in a homodyne detection setup, requiring multiple detectors. Here, we present that with an alternative approach the tilt and displacement of the deflected beam can also be reconstructed from a radio-frequency beating signal generated by the deflected beam superimposed with a frequency-shifted higher-order mode on a single detector. Numerical and analytical descriptions of the beam pointing detection concept are compared, and we present a first proof-of-principle experimental realization of an one-dimensional beam stabilization which can be extended into a two-dimensional approach by the superposition with two higher-order modes with different frequency shifts.