Andrew Stapleton

Grating-assisted coupling of optical fibers and photonic crystal waveguides

We propose and analyze a highly efficient method of coupling light from optical fibers to two-dimensional photonic crystal waveguides. Efficient coupling is achieved by positioning of a tapered fiber parallel to the linear defect, where the photonic crystal’s cladding functions as a grating coupler and provides field confinement as well. Numerical simulations indicate that better than 90% transmission is possible with a full width at half-magnitude bandwidth of 12 nm. It is shown that one can increase the bandwidth by increasing the field overlap between the two waveguides.

Quality factors in single-defect photonic-crystal lasers with asymmetric cladding layers

We present quality factors of single-defect photonic-crystal resonant cavities with asymmetric cladding layers. The resonators studied here are dielectric slabs patterned with two-dimensional photonic crystals on a sapphire substrate. Three-dimensional finite-element and finite-difference time-domain routines were used to analyze the electromagnetic properties of these cavities. We observe that high quality factors (∼800) can be obtained in these cavities for reasonable structures with thick enough dielectric slabs. This work was motivated by the need to place photonic-crystal resonators on a substrate to improve heat dissipation in photonic-crystal lasers.

Optical phase characterization of active semiconductor microdisk resonators in transmission

The optical phase characteristics of an indium phosphide (InP) vertically coupled microdisk were experimentally demonstrated. Overcoming the material losses by injecting current into the active quantum well microdisk layer has allowed us to observe the phase behavior in all three coupling regimes. The ability to tune the resonant wavelength of this device makes it suitable for use as a phase modulator or tunable optical delay element.

Calculated out-of-plane transmission loss for photonic-crystal slab waveguides

A fully three-dimensional finite-difference time domain numerical model is presented for calculating the out-of-plane radiation loss in photonic-crystal slab waveguides. The propagation loss of a single-line defect waveguide in triangular-lattice photonic crystals is calculated for suspended-membrane, oxidized-lower-cladding, and deeply etched structures. The results show that low-loss waveguides are achievable for sufficiently suspended membranes and oxidized-lower-cladding structures.

120μW peak output power from edge-emitting photonic crystal double-heterostructure nanocavity lasers

As an attempt to collect more in-plane emission power out of wavelength size two-dimensional photonic crystal defect lasers, edge-emitting photonic crystal double-heterostructure quantum well membrane lasers were fabricated by shortening the number of cladding periods on one side. 120μW peak output power was collected from the facet of the single mode laser at room temperature. Laser efficiencies were analyzed and agree very well with three-dimensional finite-difference time-domain modeling.

Experimental measurement of optical phase in microdisk resonators

The optical phase characteristics of an InP vertically coupled microdisk were experimentally demonstrated for the first time. Overcoming material losses through current injection allowed us to observe the phase behavior in all three coupling regimes.

Quality factors in single defect photonic crystal lasers with asymmetric cladding layers

We present calculations that allow the design of two-dimensional photonic crystal resonant cavities in dielectric slabs bonded to a sapphire substrate. Finite-difference time-domain (FDTD) calculations of quality factors in two-dimensional photonic crystal membranes on a sapphire substrate were performed. We considered a triangular lattice with a single missing hole, and it is the Q of the doubly-degenerate resonant mode associated with this missing hole that we were concerned with. The Q of the cavity was obtained by multiplying the resonant frequency, which was obtained from a Fourier transform of the field, by the energy stored in the cavity and then dividing by the power lost out of the cavity.

60 microWatts of Fiber-Coupled Peak Output Power from an Edge-Emitting Photonic Crystal Heterostructure Laser

An array of double-heterostructure photonic crystal QW membrane lasers was fabricated in which number of cladding periods was varied. 60 muW peak output power was collected from the facet of one device by a bare fiber.

Active Semiconductor Microdisk Vertically Coupled to a Waveguide Bus as a Polarization Rotator

Non-zero coupling coefficients between the pseudo-orthogonal modes of waveguides and microdisks lead to the possibility of preferential polarization mode conversion in these devices. Active microdisks have been demonstrated as polarization rotators based on this property.

Coupling Control in Polymer Microring Based High-Q Filters and Electro-Optic Modulators Using Photobleaching

Precise and fast post-fabrication trimming of coupling has been demonstrated using high-intensity laser photobleaching of the coupling region in high-Q passive polymer microrings vertically coupled to chromophore-doped waveguides, and in laterally coupled electro-optic ring modulators.