Optical generation of millimeter-waves using a dual-polarization emission external cavity diode laser

We report on the generation of millimeter-waves by heterodyne mixing of two wavelength tunable laser modes emitted simultaneously from a single diode laser operating in a two-arm external cavity. The modes are in the 1.55 μm range, one of them vibrates in TE and the other in TM polarization. We have measured beat-frequencies from 1 to 22 GHz, where the upper frequency is limited by the photodetector set-up. The mode wavelength separation can be tuned from approximately zero to 10 nm corresponding to beat-frequencies up to 1330 GHz. The results are qualitatively supported by theoretical analysis.