A traditional Phase Locked Loop (PLL) is an electronic circuit of which the main application is to generate precise frequencies. It is an essential building block in every radio system. E.g. in a conventional FM radio receiver, the channel selection occurs by tuning to the broadcast frequency. In practice this is done by locally generating this frequency, which is done by a PLL. Researchers have demonstrated that such a PLL can also be realized using photonic components such as lasers. We call such a system an Optical PLL (or OPLL). For most applications such as wireless, spectroscopy, radio-over-fiber... such an OPLL should be compact: ideally it is integrated as a hybrid photonic/electronic chip. However, until now such integrated OPLLs have operated at frequencies below 20 GHz. In this project we want to investigate techniques that would enable operating frequencies of 300 GHz. For this, we will introduce 3 important innovations. (1) We will incorporate new architectures that were recently invented for electrical PLLs into our OPLL. (2) We will integrate the photonics part of the OPLL on a silicon nitride platform, contrary to the traditional monolithic InP platforms used today. (3) We will use a new technology to glue the photonics part and the electrical control circuits together. This technology is called "micro-transfer printing". This technology promises extreme short interconnections and parasitic delays, hence high speeds.