High-order Microring Resonators Research Articles

High order coupled microring resonator filters for on-chip optical interconnects with steep edge response

ABSTRACT In this paper, high-order microring resonator filters coupled serially up to the 7th order are proposed for on-chip optical interconnects. This work mainly focuses on achieving a flat-top, higher out-of-band rejection ratio, and enhanced group delay value than previously demonstrated microring filters. Further, the effect of varying inter-resonator coupling coefficients on the filtering operation of wavelength 1552 nm is investigated, using the continued fraction method, and optimum conditions for coupling coefficients between ring-ring waveguides are realized to obtain steep edge response. The proposed design exhibits a minimum group delay of 7.457 ps at a coupling value of 0.04.

Optical multi-stability in a nonlinear high-order microring resonator filter

We theoretically analyze and experimentally demonstrate optical bi-stability and multi-stability in an integrated nonlinear high-order microring resonator filter based on high-index contrast doped silica glass. We use a nonlinear model accounting for both the Kerr and thermal effects to analyze the instability behavior of the coupled-resonator based filter. The model also accurately predicts the multi-stable behavior of the filter when the input frequency is slightly detuned. To understand the role of the intracavity power distribution, we investigate the detuning of the individual rings of the filter from the optical response with a pump–probe experiment. Such a measurement is performed scanning the filter with a low-power probe beam tuned a few free spectral ranges away from the resonance where the pump is coupled. A comprehensive understanding of the relationship between the nonlinear behavior and the intracavity power distribution for the high-order microring resonator filter will help the design and implementation of future all-optical switching systems using this type of filter.

Rectangular optical filter based on high-order silicon microring resonators

The rectangular optical filter is one of the most important optical switching components in the dense wavelength division multiplexing (DWDM) fiber-optic communication system and the intelligent optical network. The integrated highorder silicon microring resonator (MRR) is one of the best candidates to achieve rectangular filtering spectrum response. In general, the spectrum response rectangular degree of the single MRR is very low, so it cannot be used in the DWDM system. Using the high-order MRRs, the bandwidth of flat-top pass band, the out-of-band rejection degree and the roll-off coefficient of the edge will be improved obviously. In this paper, a rectangular optical filter based on highorder MRRs with uniform couplers is presented and demonstrated. Using 15 coupled race-track MRRs with 10 μm in radius, the 3 dB flat-top pass band of 2 nm, the out-of-band rejection ratio of 30 dB and the rising and falling edges of 48 dB/nm can be realized successfully.

High-order micro-ring resonator with perfect transmission using symmetrical Fibonacci structures.

A symmetrical Fibonacci micro-ring resonator (SFMR) has been presented to avoid the coupled resonator optical waveguide (CROW) bottle, which is a bottle-shaped distribution for high orders in transmission spectra. The SFMR features three advantages that improve filtering quality compared to that provided by traditional periodic micro-ring resonators. First, sharper resonances are obtained by eliminating the CROW bottle from the mini gaps that appear in the major-band region. Second, peaks with perfect transmission are always obtained without a radius and coupling modulation in the mini-band regions and major-band regions. Third, the full width at half-maximum of the band-edge peak decreases with the increasing generation order.

High-order microring resonators with bent couplers for a box-like filter response.

High-order microring resonator (MRR) filters with bent directional couplers are proposed and demonstrated to achieve a box-like filter response. When using bent couplers, the coupling ratio can be adjusted easily by choosing the length of the coupling region, and the excess loss is almost zero while the perimeter of the microring length is unchanged. For the present fabricated five-microring filters with bent directional couplers, the excess loss is less than 1.0 dB, the out-of-band extinction ratio is ∼36 dB, and the response has rising and falling edges as sharp as 48 dB/nm. The thermal tunability of the high-order MRR filter with a Ti-microheater is also demonstrated and the thermally tuning efficiency is about 0.10 nm/mW.

Accurate frequency alignment in fabrication of high-order microring-resonator filters

Frequency mismatch in high-order microring-resonator filters is investigated. We demonstrate that this frequency mismatch is caused mainly by the intrafield distortion of scanning-electron-beam-lithography (SEBL) used in fabrication. The intrafield distortion of an SEBL system is measured, and a simple method is also proposed to correct this distortion. By applying this correction method, the average frequency mismatch in second-order microring-resonator filters was reduced from -8.6 GHz to 0.28 GHz.

Group delay and dispersion analysis of compound high order microring resonator all-pass filter

In this paper, we propose a novel compound high order microring resonator all-pass filter employing two cascaded microrings and an assistant microring. It improves the dispersion compensation ability and provides a wide bandwidth. The group delay range is effectively extended, which provides flexibility in choosing the geometrical parameters of the microring for technical convenience and bend loss improvement. The careful design of coupling coefficients can optimize the group delay response. This device is able to provide dispersion compensation to systems such as the high speed dense wavelength division multiplexer (DWDM) optical fiber links.