The paper 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.

We demonstrate an 860 nm high brightness non absorbing mirror ridge laser fabricated using defect induced quantum well intermixing, giving an improved catastrophic optical damage level by a factor of 2.6.

We present preliminary results from a quantum well intermixed monolithically integrated multi-mode interferometer array laser which potentially offers superior near and far-field characteristics, single-mode power capability, stability, and single-wavelength operation.

The authors demonstrate a novel high brightness single-lateral mode ridge laser using quantum well intermixing to form a buried heterostructure. Increased discrimination between the fundamental and higher order modes can be achieved using the buried heterostructure to reduce the width of the gain section, enhancing fundamental mode operation. This allows the ridge width to be increased while maintaining fundamental mode operation, hence reducing the optical intensity at the facet and increasing the optical power before mirror degradation. Standard and novel buried heterostructure ridge lasers of 5- m width are compared; far-field beam profiles clearly show improved modal stability for the novel structure.

The authors demonstrate an improved catastrophic optical damage (COD) level from a ridge laser with nonabsorbing mirrors (NAMs) fabricated by quantum well intermixing. Under destructive testing conditions, the COD level of the NAM laser was improved by a factor of 2.6 compared to the standard laser, attributed to reduced absorption induced facet degradation. Verification of the degradation mechanism was confirmed by inspection and removal of damaged facets.

We demonstrate improved lateral mode stability and discrimination from a novel high brightness single-mode ridge laser using defect induced quantum well intermixing to form a self-aligned buried heterostructure.