Mesophotonics Limited

Greg Jason Parker

Majd Zoorob

Martin Charlton

James Gordon Wilkinson

Martin David Brian Charlton

John Lincoln

Maria Caterina Netti

Simon James Cox

Nicolas Perney

The invention provides a photonic structure comprising a first region () formed from a material having a first refractive index; and an array of sub-regions () formed in the first region, each sub-region having a refractive index different to the first refractive index; wherein the array of sub-regions () can be defined by a plurality of rows and columns, wherein the position of each sub-region relative to adjacent sub-regions in each row and the properties of the sub-regions across each row are defined by parameters of a first type, and the position of each row relative to adjacent rows, and the properties of the sub-regions along each column are defined by parameters of a second type; and wherein at least one parameter of a first type and at least one parameter of the second type is varied systematically and independently across the array. The present invention gives rise to structures with photonic band structures that can be tailored to a particular application. A variation in the first type of parameter has a different effect to a variation in the second type of parameter. Variation in a first type of parameter alters the diffracting properties of each row in the stack of rows. Variation in a second type of parameter affects the reflective properties of the structure. According to another aspect of the invention, a method for manufacturing photonic structures is provided including a computer optimisation process in the design stage.

Photonic band structure devices

A waveguide structure according to the invention comprises a core layer (), having a refractive index n, and an array of rods () in the core layer having a refractive index n. The refractive indices satisfy the inequality: n&#x3e;n. In a planar waveguide structure buffer () and cladding () layers are included, having a refractive index nand nrespectively. The refractive indices then satisfy the inequality: n&#x3e;n&#x3e;nand n. This condition provides greater vertical confinement of the E-field of an optical signal passing through the waveguide. Furthermore, it allows waveguides to be formed of a glassy material having a similar refractive index and core dimensions to that of a fiber. A high refractive index contrast within the photonic crystal region is used while totally eliminating the need for mode conversion to launch light in and out of the waveguide.

Optical waveguide structure

A waveguide structure () according to the invention comprises a core layer (), a cladding layer () and a buffer layer (). Sub-regions () are formed in the cladding layer () but not in the core layer (). In one dimensional applications the sub-regions are slots: in two dimensional applications the sub-regions are rods. The rods or slots may be air-filled or filled with an in-fill material, (e.g. Si). The in-fill material, if present, enhances the contrast in dielectric constant between sub-regions () and the core layer (). Sub-regions () may furthermore be formed in the portion of the buffer layer neighbouring the core layer. Slots or rods in the buffer may be air-filled or filled by an in-fill material. Substantially complete confinement of the mode in the core can be assured while still maintaining the ability to interact with the field within the photonic band structure region. Rather than perturb the majority of the field (which is confined in the core), it is possible to interact with the evanescent field in the cladding layer (or the buffer layer) without substantially affecting mode confinement.

An optical waveguide structure according to the invention comprises a core layer having a first refractive index n, an array of sub-regions within the core having a second refractive index n, the array of sub-regions giving rise to a photonic band structure within the core layer, and a cladding layer adjacent to the core layer having a refractive index n, wherein: n&#x3e;n[[&#x2203;]]&#x2267;nand n&#x2212;n&#x3e;0.1. The structure of the present invention is less lossy than prior waveguide structures having photonic band structure regions. The out of plane divergence of light in the sub-regions is reduced as compared with air holes which are typically used in photonic crystal structures. As a result more light is coupled back into the core at the sub-region/core interface. Coupling of light into the buffer layer is also reduced. Furthermore, there are added advantages over the prior art associated with the fabrication of these structures.

There is provided a planar waveguide structure () having a first core layer (), a second core layer () and a cladding layer (), wherein the cladding layer () is disposed between the first core layer () and the second core layer () to form an inter-core cladding layer (). The inter-core cladding layer () comprises a first region () having a first refractive index and an array of sub-regions () formed therein having a second refractive index. The subregions () do not extend into either the first or the second core layer, and they give rise to a photonic band structure region, which is effective to perturb an evanescent field of an optical signal propagating through the core layers.

There is provided a non-linear optical device for enhancing the bandwidth accessible in the nonlinear generation of an optical signal. The device comprises a planar optical waveguide, the planar optical waveguide being operative to generate an optical output from an optical input having an input bandwidth by means of a non-linear optical process, the optical output having a wavelength within an accessible bandwidth, wherein the planar optical waveguide is operative to enhance the accessible bandwidth such that the ratio of the accessible bandwidth to the input bandwidth is at least 4. The device is particularly applicable to broad optical continuum generation, but may also be used in a parametric oscillator or amplifier arrangement with broad tuning range.

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Brockenhurst, United Kingdom

Greg Jason Parker