Abstract: A strongly confined ridge waveguide that provides substantially reduced polarization sensitivity, without significant compromise for other waveguide characteristics such as, for example, single-mode condition, and low propagation and bending losses for the fundamental mode. The present invention considers waveguide material composition and thickness for guiding and cladding layers, bend radius, ridge width and etch depth at which the modal indices of the fundamental TE and TM modes are equal. With those parameters, the losses (e.g., the imaginary parts of the modal indices) of the fundamental and first-order modes may be calculated. By considering the previously mentioned criteria, a low-loss, single-mode ridge waveguide may be constructed in accordance with the present invention having losses of the fundamental modes in the range of less than approximately 1.

Abstract: A polarization independent optical resonator comprising a phase-shifted grating structure is disclosed and analyzed. An application as a polarization independent optical wavelength filter with ultra-narrow bandwidth and fine tunability is described.

Abstract: Improvements in grating-assisted optical filter couplers are described. In particularly, taper shapes for the gratings-assisted codirectional couplers are determined to provide an out-of-band sidelobe suppression ratio of greater than -30 dB, and a passband response that is flat and has a transmission of greater than 99.55% of the transmission at the passband center, over a wavelength range of 25% of the half-power bandwidth.The interaction strength defining the optimized spectral characteristics is given byK.sub.1 (z)=A.sub.1 e.sup.-.alpha..sbsp.1.sup.(z-z.sbsp.i.sup.).spsp.2 +A.sub.2 e.sup.-.alpha..sbsp.2.sup.(z-z.sbsp.2.sup.).spsp.2 A.sub.3 e.sup.-.alpha..sbsp.3.sup.(z-z.sbsp.3.sup.).spsp.2 0<z<1where K.sub.1 (z) is the normalized interaction strength along the propagation direction, and the constant coefficients areA.sub.1 =8.774; A.sub.2 =-3.45; A.sub.3 =1.183;.alpha..sub.1 =51.87; .alpha..sub.2 =34.49; .alpha..sub.3 =20.63;z.sub.1 =0.28; z.sub.2 =0.60; z.sub.3 =0.75.

Abstract: An optical directional coupler filter having at least two guides; an input guide and a coupled guide. The spacing between the guides and hence the interactive strength is tailored so as to provide ultralow sidelobe levels at a narrow spectral bandwidth. A formula has been derived with respect to the tapered shape function of the waveguides in order to arrive at the optimum results.