Richard J. E. Taylor

Epitaxially Regrown GaAs-Based Photonic Crystal Surface-Emitting Laser

A GaAs-based epitaxially regrown photonic crystal surface-emitting laser is proposed and demonstrated at room temperature. The photonic crystal band-structure is mapped through the angular dependence of subthreshold electroluminescence, allowing the photonic crystal coupling coefficients to be determined.

Optimisation of Coupling between Photonic Crystal and Active Elements in an Epitaxially Regrown GaAs Based Photonic Crystal Surface Emitting Laser

The waveguide design of a GaAs based, epitaxially regrown photonic crystal surface emitting laser is discussed so as to optimise the coupling of the photonic crystal and the mode overlap with the quantum wells. Design criteria include the positioning of the quantum well and the photonic crystal layers, and the effect of varying aluminium composition in the lower cladding layer. Room-temperature, pulsed laser oscillation is demonstrated.

Band structure and waveguide modelling of epitaxially regrown photonic crystal surface-emitting lasers

In this paper we describe elements of photonic crystal surface-emitting laser (PCSEL) design and operation, highlighting that epitaxial regrowth may provide advantages over current designs incorporating voids. High coupling coefficients are shown to be possible for all-semiconductor structures. We introduce type I and type II photonic crystals (PCs), and discuss the possible advantages of using each. We discussed band structure and coupling coefficients as a function of atom volume for a circular atom on a square lattice. Additionally we explore the effect PC atom size has on in-plane and out-of-plane coupling. We conclude by discussing designs for a PCSEL combined with a distributed Bragg reflector to maximize external efficiency.

All-Semiconductor Photonic Crystal Surface-Emitting Lasers Based on Epitaxial Regrowth

The realization of all-semiconductor epitaxially regrown photonic crystal (PC) surface-emitting lasers is reported. PC coupling strengths, band structure, optimization of epitaxial regrowth, and operating characteristics are discussed. Room temperature operation allows agreement between theoretical and experimental band structure to be confirmed.

Electronic control of coherence in a two-dimensional array of photonic crystal surface emitting lasers

We demonstrate a semiconductor PCSEL array that uniquely combines an in-plane waveguide structure with nano-scale patterned PCSEL elements. This novel geometry allows two-dimensional electronically controllable coherent coupling of remote vertically emitting lasers. Mutual coherence of the PCSEL elements is verified through the demonstration of a two-dimensional Young’s Slits experiment. In addition to allowing the all-electronic control of the interference pattern, this type of device offers new routes to power and brightness scaling in semiconductor lasers, and opportunities for all-electronic beam steering.

Coherently Coupled Photonic-Crystal Surface-Emitting Laser Array

The realization of a 1 × 2 coherently coupled photonic crystal surface emitting laser array is reported. New routes to power scaling are discussed and the electronic control of coherence is demonstrated.

Gallium nitride super-luminescent light emitting diodes for optical coherence tomography applications

Optical coherence tomography (OCT) exploits the coherent properties of light to permit noninvasive and in situ imaging of biological tissues. By expanding the range of OCT light sources from the traditional telecoms wavelengths to include ∼400 nm gallium nitride (GaN) based superluminescent light emitting diodes (SLEDs) subcellular axial and lateral resolution could be achieved, provided enhanced bandwidth is also achieved. Due to the focus on high-power applications for GaN SLEDs, there has been limited work on increasing the source bandwidth. In this paper, we demonstrate for the first time a ∼400 nm GaN SLED with >10 nm bandwidth employed within an OCT system, where an axial resolution of ∼7 μm is achieved. Bespoke GaN SLEDs suggest that <4 μm axial resolution imaging is imminent for short wavelength devices.

3D FDTD modelling of photonic crystal surface emitting lasers

We investigated the beam divergence in far-field region, diffraction loss and optical confinement factors of semiconductor photonic crystal surface emitting lasers containing either InGaP/GaAs or InGaP/air photonic crystals. The maximum in-plane feedback in PCSELs with InGaP/GaAs PCs has been observed at the ratio between PC atom radius and the lattice constant of 0.2 and 0.38. The surface emission grows as the size of atom increases.

Effective index modelling of photonic crystal surface-emitting lasers (Conference Presentation)

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.

Room-temperature capsule-shaped wavelength-scale metal-clad laser operating at 1550 nm

We fabricate a capsule-shaped metal-clad wavelength-scale cavities on InP and demonstrate room-temperature lasing at 1550-nm wavelength. By introducing an optimized curvature to the sidewalls of a conventional rectangular metal-clad laser, we effectively reduce the optical loss of transverse-electric (TE) mode and experimentally confirm, for the first time, clear improvement in side mode suppression ratio and slope efficiency of the laser under pulsed optical pumping.