Patent ID: 7609919

Claim:
A coupling arrangement for an effective-ridge lateral-coupling surface etched grating waveguide structure comprising: a multiple effective-ridge waveguide comprising: a slab waveguide structure comprising of a number of layers arranged to provide a vertical confinement for an optical signal having a wavelength within a predetermined operating wavelength range, propagating within the said structure in the direction parallel to the layers; a central ridge waveguide; the central ridge waveguide consisting of a continuous strip of the slab waveguide structure; the central ridge waveguide providing a first aspect of horizontal confinement of the optical signal propagating within the slab waveguide; at least a side ridge; the at least a side ridge consisting of a continuous strip of the slab waveguide structure and providing a second aspect of horizontal confinement of the optical signal propagating within the slab waveguide; a surface-etched grating comprising: a periodic sequence of parallel segmented trenches etched from the top surface of the slab waveguide structure, such that intact segments of the slab waveguide structure form strips of intact material providing a higher refractive index to the optical signal than that of sections of the slab waveguide structure with etched segments; wherein, the effective-ridge lateral-coupling surface etched grating waveguide supports at least one laterally and vertically confined mode of a plurality of modes at any wavelength within the predetermined operating wavelength range; and, the design of the multiple effective-ridge waveguide and surface-etched grating are adjusted to achieve an overlap exceeding a predetermined threshold between an optical mode field of a laterally and vertically confined mode of the plurality of modes of an optical signal propagating within the effective-ridge lateral-coupling surface etched grating waveguide and the surface-etched grating.