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An eight-channel add-drop filter using vertically coupled microring resonators over a cross grid

An eight-channel add-drop cross-grid vertically coupled microring resonator (VCMRR) filter is proposed and demonstrated. The cross grid comprises a grid-like array of buried channel waveguides which perpendicularly cross through each other, VCMRRs at each of the cross-grid nodes serve as the wavelength selective add-drop filters. Measured crosstalk levels at the crossings are typically less than -30 dB. Rings with a nominal radius of 10 /spl mu/m are used to achieve a free-spectral range of 20 nm and optical bandwidths of 1 nm, while changes of the radii in increments of 50 nm lead to a nominal channel spacing of 5.7 nm.

Microring resonator arrays for VLSI photonics

The analytic theory governing the complete scattering response of two-dimensional (2-D) microring resonator arrays is developed, The method is applicable to arbitrary interconnections of general four-port, single polarization nodes. An 8/spl times/8 cross-grid array of vertically coupled glass microring resonators is fabricated for test purposes.

Vertically coupled glass microring resonator channel dropping filters

Air-clad glass microring resonators vertically coupled to buried channel waveguides are experimentally investigated. Ring radii of 10 /spl mu/m, and channel drop bandwidths of 5 nm are reported. Vertical coupling eliminates the need for the etching of fine features, and relaxes the alignment of the resonator with respect to the input and output bus waveguides.

Wavelength trimming of a microring resonator filter by means of a UV sensitive polymer overlay

Trimming of the resonant wavelength of a vertically coupled glass microring resonator channel dropping filter with a photo-induced refractive index change in a dip coated polymer overlay is reported. In this letter, the glass microring resonator has a radius of 19 /spl mu/m, a free-spectral range of 10 nm, and a Q value of 800. The maximum wavelength shift observed is 9 nm, which is yielded through an absolute bulk index change in the polymer of 0.044. Trimming is a continuous function of exposure time and dose.

Second-order filter response from parallel coupled glass microring resonators

Ring resonators are coupled in parallel in order to obtain a second order type of wavelength response. The phase relationship between the rings determines the details of the spectral response. The rings used in the experiment have radii of 25 /spl mu/m and are fabricated from compound glass having an index of 1.539. Several resonances are observed to have double peaked box-like response.

Cascaded microring resonators for crosstalk reduction and spectrum cleanup in add-drop filters

The role of cascaded filters for spectrum cleanup and crosstalk reduction in add-drop filters is addressed experimentally for microring resonator cross-grid technology. The fabricated devices consist of glass microring resonators 10 /spl mu/m in radius vertically integrated above a cross-grid waveguide array. Sharper linewidth rolloff and flattened passband responses are observed. The ratio of 15 to 3 dB bandwidth of a cascaded double filter is reduced by a factor of 3 compared with the single-filter case. Because of the very small dimensions of the resonators, the use of multiple filters to improve the spectral response consumes negligible chip space.

Temperature insensitive vertically coupled microring resonator add/drop filters by means of a polymer overlay

The temperature dependence of vertically coupled glass microring resonator add/drop filters is investigated. Measurements show that the passband of the air-clad microring resonator filter increases with temperature at a rate of 0.0137 mm//spl deg/C. Using a PMMA-TFMA polymer that has an opposite refractive index temperature gradient than glass as the overlay of the microring resonator, the temperature dependence of the filter is compensated to -0.0025 nm//spl deg/C in the operation range of 25/spl deg/C to 55/spl deg/C.

59-nm trimming of center wavelength of ARROW-type vertical coupler filter by UV irradiation

An antiresonant reflecting optical waveguide (ARROW)-type vertical coupler filter (VCF) with a polysilane cover layer is designed and fabricated to demonstrate the trimming of the center wavelength of the filter by ultraviolet (UV) irradiation. The propagation constant of the upper waveguide of the VCF was modified by UV irradiation on the polysilane cover in the presence of oxygen. The refractive index of polysilane can be adjusted from 1.448 to 1.427 by the exposure time of the UV irradiation. A wide trimming range of 59 nm (1567.5 nm to 1508.8 nm) of center wavelength is demonstrated.

High-coupling efficiency vertical ARROW coupler with large tolerance and short coupling length for three-dimensional optical interconnects

A compact ARROW-type vertical coupler for three-dimensional optical interconnects was demonstrated. The refractive index and thickness of intermediate cladding were optimally designed to achieve large fabrication tolerance and short coupling length with high coupling efficiency. Very short coupling length of 800 /spl mu/m and high coupling efficiency of 96% were experimentally demonstrated.

Planarization of Film Deposition and Improvement of Channel Structure for Fabrication of Anti-Resonant Reflecting Optical Waveguide Type X-crossing Vertical Coupler Filter

To realize a low-sidelobe narrow-band Anti-resonant reflecting optical waveguide (ARROW)-type vertical coupler filter, the dependence of the refractive index and thickness profiles of compound glass films, deposited by a magnetron RF sputtering technique, on the mixture ratio of Ar and O2 gases was investigated. First, the depth profile of the refractive index of SiO2 films was planarized using pure O2 gas. Next, the lateral profiles of the refractive index and thickness of compound glass films were planarized by optimizing the gas mixture ratio of Ar and O2. When the mixture ratio was Ar : O2 = 1 : 3, the index variation of the Corning 7059 glass film was vastly improved from 0.3% to 0.05%, and the thickness variation was also improved from 9.0% to 4.0%. A similar improvement was also achieved for SK1 glass (from SCHOTT) and the Ta2O5–SiO2 binary glass system. A low sidelobe ARROW-type vertical coupler filter (VCF) with Corning 7059 glass and SK1 glass cores was demonstrated, using these deposition techniques and a wet chemical etching technique. In addition, the planarization technique of stripe-lateral-confinement (SLC)-ARROW waveguide was developed using a lift-off technique. A narrow band ARROW-type vertical coupler filter with Ta2O5–SiO2 cores was achieved by the lift-off and reactive ion etching (RIE) techniques.