Frequency tunable beat note from a dual-polarization emitting external cavity diode laser

A method is presented to generate tunable millimetre waves by photomixing one TE mode and one TM mode of a dual-polarization external cavity diode laser emitting in the 1.55 μm wavelength domain. Beat notes in the frequency range 0.2 to 60GHz have been measured where the upper frequency is limited by the detector system bandwidth only. The frequency and amplitude stability are investigated. Typical beat intensity fluctuations are within 0.5 dB. The frequency stability is around 5MHz. The relative intensity noise of a TE and a TM mode was measured and a correlation found around multiples of the cavity roundtrip frequency and in the low frequency regime. Theoretical calculations show qualitative agreement with the measurement results. This revised version was published online in November 2006 with corrections to the Cover Date.