Photonic crystal surface emitting lasers (PCSEL) are of interest in order to achieve large area single mode operation, excellent beam quality, and high output powers. Coherent PCSEL arrays have also been realised and lasing mode control of PCSELs has been demonstrated by using external in-plane feedback.
However, the design and analysis of PCSELs has been limited by current modelling techniques. The plane wave expansion method is only applicable to infinite structures whilst the finite difference time domain method is computationally intensive especially when modelling large area, three dimensional finite devices. Other analytical approach, such as coupled mode analysis, leads to significant mathematical complication. None of these are well suited to accurately describing complex PCSEL devices, nor the effect of in-plane feedback.
We introduce a general quasi-analytical model based on the separation of variables and a quasi-scalar field distribution. The multilayer planar structure in the growth direction is accounted for by computing the effective indices corresponding to the in-plane bound guided modes. This operation results in a sculpted, periodic index distribution. Next, by first assuming index uniformity along the z-axis, a piecewise constant multilayer periodic media results. An effective wave impedance of the waves supported in this structure are then computed and used to construct the 3D device. In this way, the final device characteristics account for the 2D periodic photonic crystal media.
We compare our modelling to other methods, and various experimental reports. In particular we focus upon the effect of external in-plane feedback on PCSELs.
All-semiconductor photonic crystal surface-emitting lasers (PCSELs) operating in CW mode at room temperature and coherently coupled arrays of these lasers are reviewed. These PCSELs are grown via MOVPE on GaAs substrates and include QW active elements and GaAs/InGaP photonic crystal (PC) layer situated above this active zone.
Atoms of triangular shapes have been shown to increase optical power from the PCSEL but are also shown to result in a competition between lasing modes. Simulation shows that the energy splitting of lasing modes is smaller for triangular atoms, than for circles making high power single-mode devices difficult to achieve.
In this work we experimentally investigate the effect of lateral optical feedback introduced by a facet cleave along one or two perpendicular PCSEL edges. This cleavage plane is misaligned to the PC resulting in a periodic variation of facet phase along the side of the device.
Results confirm that a single cleave selects the lowest threshold 2D lasing mode, resulting in a ~20% reduction in threshold current and favours single-mode emission. The addition of a second cleave at right-angles to the first has no significant effect upon threshold current.
The virgin device is shown to have a symmetric far-field (1 degree) whilst a single cleave produces a 1 degree divergence perpendicular to cleave and 5 degree parallel to cleave. The second orthogonal cleave results in the far field becoming symmetric again but with a divergence angle of 1 degree indicating that single-mode lasing is supported over a wider area.
We investigate the beam divergence in far-field region, diffraction loss and optical confinement factors of all-semiconductor
and void-semiconductor photonic-crystal surface-emitting lasers (PCSELs), containing either
InGaP/GaAs or InGaP/air photonic crystals using a three-dimensional FDTD model. We explore the impact
of changing the PC hole shape, size, and lattice structure in addition to the choice of all-semiconductor or
void-semiconductor designs. We discuss the determination of the threshold gain from the diffraction losses,
and explore limitations to direct modulation of the PCSEL.
980 nm GaAs-based photonic crystal surface emitting lasers containing all semiconductor GaAs/InGaP and GaAs/air photonic crystals (PC) inside their cavity are theoretically investigated. We use a combination of an average index approach and optical coupled mode theory to optimize the PC interaction with optical modes of the laser waveguide and draw guidelines for design of PCSELs based on a range of material systems and operating wavelengths. Results show that the all-semiconductor PC provides a higher coupling with the optical mode in most cases.
Recently, there has been much interest in a novel type of device, the 2D photonic crystal surface emitting laser (PCSEL).
For commercialization of these devices a robust and high reliability manufacturing method is required. Previous GaAs
wafer fusion and GaN regrowth techniques have utilised voids within the photonic crystal which suffer from reliability
and reproducibility issues. We demonstrate a GaAs based PCSEL structure which uses epitaxial regrowth to completely
infill the etched structure. We discuss the design, epitaxy, and operating characteristics of these devices over a range of