The work describes recent progress in the design, simulation, implementation and characterisation of photonic crystal (PhC) GaAs-based quantum cascade lasers (QCLs). The benefits of applying active PhC confinement around a QCL cavity are explained, highlighting a route to reduced threshold current operation. Design of a suitable PhC has been performed using published bandgap maps; simulation results of this PhC show a wide, high reflectivity stopband. Implementation of the PhC for the device is particularly difficult, requiring a very durable metallic dry etch mask, high performance dry etching and a low damage epilayer-down device mounting technique. Preliminary shallow etched PhC QCLs demonstrated the viability of current injection through the metal etch mask and the device mounting technique. Development of the etch mask and dry etching have demonstrated a process suitable for the manufacture of deep etched PhC structures. All the necessary elements for implementing deep etched PhC QCLs have now been demonstrated, allowing for the development of high performance devices.