Abstract. In this work, a photonic physical unclonable function module, based on an optical waveguide, is demonstrated. The physical scrambling mechanism is based on the random and complex coherent interference of high order optical transverse modes. The proposed scheme allows the generation of random bitstrings, through a simple wavelength tuning of the laser source, that are suitable for a variety of cryptographic applications. The experimental data are evaluated in terms of unpredictability, employing typical information theory benchmark tests and the NIST statistical suit.