Andrew Greenwell

Multiline two-dimensional guided-mode resonant filters

A novel multi-line filter using two-dimensional guided mode resonant (2D-GMR) filter is proposed. The locations of resonances are specifically controlled by modifying only the periodicity of the grating and other physical dimensions of the structure.

Multiple wavelength resonant grating filters at oblique incidence with broad angular acceptance.

Multilayer, multimode waveguides are utilized in resonant grating filters having a broadened angular acceptance bandwidth for multiple wavelengths at a single oblique angle of incidence. It is shown that the waveguide grating structure should support a few leaky modes in order to support a multiwavelength resonant filter at oblique incidence with broadened angle acceptance at each wavelength.

Broadening the angular tolerance in two-dimensional grating resonance structures at oblique incidence

Broadening of the angular response of two-dimensional (2D) guided mode resonant spectral filters at oblique incidence is investigated. Coupling into multiple fundamental guided resonant modes having the same propagation constant but propagating in different planes (inherent multiple-plane diffraction by 2D gratings) is shown to significantly broaden the angular tolerance while maintaining narrow linewidth. Resonances have symmetric and broad angular responses when the incident wave is coupled to four resonant modes in a structure with a hexagonal grating pattern. Further broadening is implemented by enhancing the second Bragg diffraction of the 2D grating structure. Resonance with a narrow spectral linewidth (Dlambda(FWHM) approximately 1.6 x 10(-4)lambda(0)) and angularly tolerant to an ~6 mum beam diameter is obtained. A second approach utilizing a dual 2D grating configuration with a second grating on the substrate side is shown to increase the lateral confinement, causing the merging of two successive resonant bands. This results in further improvement of the angular/spectral linewidth ratio by ~80%.

Efficient rigorous calculations of power flow in grating coupled surface-emitting devices

We present an extremely efficient rigorous vector electromagnetic analysis of field distribution and power flow in grating coupled surface emitting structures. The developed technique is based on constructing an artificially periodic structure of identical grating coupled device cells separated by anisotropic magnetic/electric perfect matching layers. The resulting periodic multi-layered structure is analyzed using the RCWA combined with a very efficient scattering matrix recursive technique. Calculated distributions of the electric and magnetic field components within the structure as well as the fields coupled into the output regions and into the substrate for typical devices are presented. Field distribution and power flow in the longitudinal and in the transverse directions in the structure are determined for the first time to our knowledge.

Control of resonance separation over a wide spectral range in multiwavelength resonant grating filters

The spectral separation of resonances within multiwavelength resonant grating filters is studied through the use of a grating layer with constant structural parameters in combination with single-layer, multimode waveguides and multilayer, multimode waveguides. The use of multilayer, multimode waveguides are shown to provide the ability to control resonance separations for multiwavelength filters from hundreds of nanometers to only a few nanometers.

Novel design to increase the angular tolerance of grating resonance devices at oblique incidence

Guided-mode resonant (GMR) structure using hexagonal-lattice grating is proposed to enhance angular tolerance of resonances at oblique incidence. Exciting radial-propagation modes, resonances with high angular tolerance (~1deg) and narrow spectral bandwidth (~0.3 nm) are achieved.

All-dielectric unidirectional dual-grating output coupler

A novel concept for an all-dielectric unidirectional output double-grating coupler is proposed and rigorously analyzed. In addition to a superstrate side grating, a second grating is placed on the substrate side. The periodicities of the gratings are chosen such that no propagating diffracted orders are present outside the structure in the superstrate region and only a single order is present outside the structure in the substrate region. The concept provides a robust output coupler requiring neither phase-matching between gratings nor any resonances in the structure, and is very tolerant to potential fabrication errors. Up to 96% coupling efficiency from the substrate-side grating is obtained over a wide range of grating properties.

Spectral response of guided mode resonant devices with gain or loss

The spectral response is presented for resonant reflection/transmission or resonant absorption of guided mode resonant devices with the addition of a uniform gain or loss.

Multi-line two-dimensional guided mode resonant filters

A novel multi-line filter using two-dimensional guided mode resonant (2D-GMR) filter is proposed. The locations of resonances are specifically controlled by modifying only the periodicity of the grating and other physical dimensions of the structure.

Multi-Line Guided Mode Resonant Filters with Controlled Spectral Separation

Two-dimensional guided mode resonant filter with multiple wavelength resonances is presented. Wide spectral separation between resonances up to 23% of the short resonant wavelength is achieved by modifying the grating periodicity and other physical dimensions.