Stephen J. Sheard

Waveguide couplers using parallelogramic-shaped blazed gratings

Abstract A novel type of waveguide coupler with a parallelogramic-shaped grating is investigated. Analysis shows that this type of coupler provides a stronger radiation factor and higher coupling efficiency than conventional sawtooth grating couplers. In addition, the radiation factor and the blaze angle of a parallelogramic grating can be independently designed.

Focusing waveguide grating coupler using a diffractive doublet

A novel focusing waveguide grating coupler comprising an integrated uniform grating coupler and binary-phase-only diffractive lens is proposed, designed, and fabricated. Experimental results are also presented to demonstrate the device performance. This device is in direct competition with single-element focusing grating couplers defined by direct-write electron-beam lithography and its structure is attractive because the fabrication procedure is better suited for mass production.

Integrated-optic array illuminator: a new design for guided-wave optical interconnections

An integrated array illuminator can be used not only as an opticalpower distributor for an array of guided-wave optic devices but also asa key element for guided-wave optical interconnections. We presenta new design for an integrated-optic array illuminator with focusingwaveguide diffractive doublet arrays. This integrated arrayilluminator allows independent optimizations of efficient and uniformoptical power distribution and focusing performance. Furthermore, the device can be fabricated with all-optical lithographic technologyand hence has the advantages of mass production with lowcost.

Demonstration of guided-wave optical fan-out using waveguide diffractive optical system

Abstract Guided-wave two-dimensional optical fan-out has been experimentally demonstrated by using a waveguide diffractive doublet consisting of a uniform grating coupler and a diffractive optical element. Design of this waveguide diffractive doublet and device fabrication results are also presented.

A configuration for guided-wave excitation into a disposable integrated-optic head

A configuration is proposed for exciting a guided wave in a waveguide on a disposable integrated-optic head. Applications are towards sensor devices where the active component is best manufactured as a cheap disposable unit. In our approach a waveguide coupling edge is separated from the main substrate end so as to protect this optical surface from damage during handling and to ensure that high coupling efficiency is obtainable for the disposable units. A coded trench marker is introduced on both sides of the waveguide coupling edge to obtain error signals for actively aligning the light source with the disposable waveguide. A demonstrator was fabricated and the error detection principle was experimentally confirmed.

RADIATION CHARACTERISTICS OF WAVEGUIDE DIFFRACTIVE DOUBLETS

The radiation characteristics of waveguide diffractive doublets consisting of double gratings located on two surfaces of waveguide cladding film are modeled based on a singular perturbation method. We determine the conditions under which the presence of the upper grating does not affect the radiation characteristics of the waveguide diffractive doublet as a whole. This allows independent performance of the upper grating, which may be replaced by a general diffractive optical element, and of the lower grating as a waveguide grating coupler. The results obtained provide an alternative method for determining the thickness of cladding film in the waveguide diffractive doublets for guided-wave manipulation.

Integrated waveguide diffractive doublet for guided-wave manipulation.

An integrated waveguide diffractive doublet consisting of a uniform grating coupler and a diffractive optical element is proposed. Design of this waveguide diffractive doublet for guided-wave manipulation is described in detail. Experimental results for a fabricated waveguide diffractive doublet are also presented to demonstrate the device principles. It was found that this waveguide diffractive doublet can enhance device functionality while remaining simple and compact and having a planar structure. Furthermore, this device can be fabricated by use of all-optical lithography.

Two-dimensional wavelength routing for transparent optical wireless networking

In this article a novel system architecture that uses a combination of wavelength and spatial diversity for indoor infrared wireless communications is presented. This configuration promises to fully exploit the available bandwidth of optics and demonstrate all-optical networking. Electronic processing is restricted to mobile terminals, with base stations potentially remaining passive, without any conversion between optics and electronics. For the downlink, multiple transmitter beams with different wavelengths are steered from the fiber infrastructure through the base station to mobile terminals located in different positions. An optimum combination of diffractive optics and reflective optics (a diffraction grating and an array of mirrors) can flexibly steer each transmitter beam and enable full control over the required coverage pattern. For the uplink, in the transmitter, another grating and an array of mirrors can direct multiple beams upward from different mobile users toward the base station. System simulation shows that the downlink has the potential to approach 10 Gbit/s, while maintaining wide-area coverage (such as in a room of 3m×4m×4m) with the help of fine optical tracking. System modeling indicates that the uplink is more susceptible to power losses than the downlink, but the utilization of dynamic beam steering in the uplink can suppress power losses to a tolerable level (e.g. below 30dB). An array of 16 mirrors has been designed to implement point-to-point beam steering in a room of 3m×1m×1m. Two-dimensional coverage patterns measured at a distance of 0.5 m and 1.5 m coincide with simulation results. Operation at 1 Gbit/s has been demonstrated successfully for tracking in two dimensions.

Grating-assisted waveguide chip-to-chip interconnects

This paper examines two different approaches for grating assisted optical interconnects between waveguides composed of dissimilar materials, i.e. evanescent and projection coupling. For evanescent coupling the waveguides have to be sufficiently close to allow overlap of the optical modes, whereas projection coupling has the advantage of allowing the waveguides to be separated by a much larger distance. In both cases we assume that phase matching is achieved using surface relief gratings. This paper compares the performance of these two methods using theoretical modelling. Results show the effects of nonparallelism with regard to the manufacture of interconnecting networks. For projection coupling an optimal design for the grating structure is proposed which combines high efficiency and device compactness.

High-performance circular grating-coupled surface emitter with focused output beam

The modal performance of focusing circular grating-coupled surface-emitting lasers has been investigated. Both the effects of reducing the resonator diameter and introducing an unpumped indentation in the center of the resonator have been studied. We have found that inclusion of such an unpumped central indentation can greatly improve the spatial mode behavior, resulting in a very uniform near field intensity, single wavelength emission, and a focused spot size only 1.5 times the diffraction limit for a laser oscillating in the fundamental circular mode. Our measurements at different drive currents show that the modal behavior of the laser is stable up to at least three times the threshold current, and based on the near and far-field intensity distributions, the laser is possibly lasing simultaneously in two orthogonal first order circular modes. Reducing the resonator diameter of lasers without an unpumped central indentation does not offer similar improvement to the modal behavior.