FREQUENCY TUNABLE BEAT NOTE FROM A DUAL-POLARIZATION EMITTING EXTERNAL-CAVITY DIODE-LASER

A method is presented to generate tunable millimetre waves by photomix ing one TE mode and one TM mode of a dual-polarization external cavity diode laser emitting in the 1.55 mu m wavelength domain. Beat notes i n the frequency range 0.2 to 60 GHz have been measured where the upper frequency is limited by the detector system bandwidth only. The frequ ency and amplitude stability are investigated. Typical beat intensity fluctuations are within 0.5 dB. The frequency stability is around 5 MH z. The relative intensity noise of a TE and a TM mode was measured and a correlation found around multiples of the cavity roundtrip frequenc y and in the low frequency regime. Theoretical calculations show quali tative agreement with the measurement results.