This tutorial describes the transmission, group delay time and quadratic dispersion properties of the four basic building blocs of optical filters built using ring resonators. These building blocs are single-ring resonators in either two-port (all-pass) or four-port (add/drop filter) configuration. The effect of waveguide and coupler loss is included throughout. Explicit expressions to compute the complex amplitude of the circulating wave in the ring, the Q factor, the finesse and the insertion loss are also given. Attention is drawn to the similarities between the ring resonator the Fabry-Pe/spl acute/rot resonator and the Gires-Tournois interferometer. Material properties and fabrication technology are not reviewed.

Transmission, group delay, and dispersion in single-ring optical resonators and add/drop filters-a tutorial overview

A key device in all-optical networks is the optical filter. A ring resonator filter with an integrated semiconductor optical amplifier (SOA) on the basis of GaInAsP-InP has been investigated and fabricated. A required passband shape of loss-compensated ring resonator filters can be custom-designed by the use of multiple coupled resonators. Results of single-, double-, and triple-ring resonators with integrated SOAs with free spectral ranges of 12.5, 25, and 50 GHz, respectively, are presented. A box-like filter response is obtained by the double- and triple-ring resonators using specific coupling coefficients.

Optical filters based on ring resonators with integrated semiconductor optical amplifiers in GaInAsP-InP

The filter response of single-ring resonators with integrated semiconductor optical amplifiers based on GaInAsP-InP is presented. The devices with free spectral ranges of 25 and 50 GHz have the form of a racetrack. An on-off ratio of 20 dB, a full-width at half-maximum of 12 and 24 pm, a finesse of 17, and a Q factor of 130,000 and 65,000, respectively, have been achieved. The tuning to a specific wavelength is performed by using integrated Pt-resistors.

High-Q channel-dropping filters using ring resonators with integrated SOAs

Micro-ring resonator based all-optical reconfigurable logic operations

A monolithic single-mode GaInAsP-InP double microring resonator coupled laser is demonstrated for the first time. The laser comprises two passive ring resonators, semiconductor optical amplifiers in the bus waveguides, and 3-dB codirectional couplers. The laser has an output power of 0.5 mW with a sidemode supression ratio of >35 dB. The tunability is demonstrated using integrated platinum resistors on top of the waveguides in the rings.

A GaInAsP-InP double-ring resonator coupled laser

A racetrack shaped double ring resonator (DRR) filter is demonstrated with radii of 200 µm. The double ring resonator contains two -3 dB multimode interference (MMI) couplers for I/O coupling and a -13 dB codirectional coupler in between the rings. A free spectral range of 50 GHz has been realized. A simulation model has been developed to describe the DRR. As fabrication tolerances do not allow the realization of two identical rings with required nm-circumference accuracy in the resonator, a frequency alignment of the resonator is indispensable. The resonance frequency tuning is performed thermally using platinum resistors which have been placed on top of the waveguides in both rings. An on-off ratio increase has been achieved of more than 3 dB, resulting in a total on-off ratio larger than 18 dB. The frequency alignment is inevitable in the case of multiple coupled micro ring resonators.

https://iopscience.iop.org/article/10.1143/JJAP.41.1186/pdf

Resonance Frequency Tuning of a Double Ring Resonator in GaInAsP/InP: Experiment and Simulation

Compact integrated microring resonators are promising candidates for various applications in optical signal processing and communication such as optical filters, wavelength (de)multiplexers, single mode sources, dispersion compensators and wavelength converters. Active GaInAsP/InP material is particularly suited for the fabrication of "lossless" filter devices as well as novel laser components with outstanding performance. Design, technology as well as transmission / emission mode characteristics for typical applications are sketched and summarized.

Active ring resonators based on GaInAsP/InP

Miniaturization of waveguide circuits is inherently connected with the implementation of highly confined waveguides as one prerequisite for the building of sharp bends and optical microring circuits. Integrated optical ring resonators are promising candidates for compact optical filters and wavelength (de)multiplexers. Their realization in active semiconductor material opens the potential to verify "lossless" filter devices as well as novel laser components with outstanding performance. Since ring resonators do not require facets or gratings for optical feedback they are particularly suited for monolithic integration. Design and technology for device fabrication are summarized. Recent results on transmission and emission mode characteristics of fabricated passive ring resonators as well as gain-included "all-active" resonators in the transmission and emission mode are presented.

InP-based high index waveguides on GaInAsP/InP for applications in active/ passive ring resonators

A key device in all-optical networks is the optical filter. Ring resonator filters on the basis of GaInAsP / InP with improved filter response and increased functionality using integrated semiconductor optical amplifiers are presented.

Channel dropping filter based on ring resonators and integrated SOAs

A solderable metal eutectic (ME) with a melting point in the range below 350 degrees C is used as a frictional coupling component, and forms a low-resistance connection with connecting components (CC1,CC2). This is achieved by applying the metal eutectic to one of the connecting components and then activating the solder connection by moderate supply of heat which does not damage the semiconductor layer structure (SS).

Frictional coupling of transfer wafer to semiconductor layer structure for manufacture of ultra-compact optical components, by applying metal eutectic and heating to activate solder connection

Dominik Gerhard Rabus

Papers

Resonance Frequency Tuning of a Double Ring Resonator in GaInAsP/InP: Experiment and Simulation

Active ring resonators based on GaInAsP/InP

InP-based high index waveguides on GaInAsP/InP for applications in active/ passive ring resonators

Channel dropping filter based on ring resonators and integrated SOAs

Frictional coupling of transfer wafer to semiconductor layer structure for manufacture of ultra-compact optical components, by applying metal eutectic and heating to activate solder connection