| 摘要 |
<p>A thin-film waveguide lens and a wavelength division multiplexer/demultiplexer (1) embodying such lens. The thin film waveguide lens comprises a thin-film waveguide with end planes essentially normal to the lens axis. A plano-convex overlay layer integral with the waveguide extends the length of the waveguide along the axis, its profile being selected so as to produce a graded effective refractive index in the lens in order to collimate focussed rays and focus collimated rays entering at one end plane for substantially collimated or focussed arrival at the other end plane. The multiplexer/demultiplexer (1) comprises the above thin-film waveguide lens, with one of the end planes constituting an entrance/exit plane (A A') for receiving optical fibres (F1, F2, F3) in an abutting connection, and the other end plane (B B') bearing a diffraction/reflection grating (5). In accordance with the preferred embodiments, the shape of the plano-convex overlay layer is such as to provide an effective index of refraction profile in the waveguide according to the formula n = n0sech(gr), where n is the effective refractive index at the distance r from the axis of the waveguide, n0 is the effective refractive index at the waveguide axis, and g is a constant equal to π/2f, where is the focal length of the lens, being essentially the distance between end planes.</p> |
