Research On Optical Filter And Switch Based On Silicon Microresonators

Silicon integrated circuit is the leading technology in the development of the electronics industry and has numerous applications in various fields.With the development of high-performance computing and high-speed interconnect,copper wires show increasing limitations in high-speed transmission.Due to the high speed and long distance transmission,optical interconnect is considered as a promising solution.To obtain cost-efficient optical solutions,integrated photonics becomes a hot research topic in both the academy and industry.Among various integrated photonic technologies,silicon photonics has attracted much attention due to its compatibility with the mature fabrication processes of silicon integrated circuit.Silicon microresonators offer competitive advantages including compact footprint,low power consumption,and wavelength selectivity,which have wide applications in optical communication system.In this thesis,we present our work on optical filters and switches based on silicon microresonators.We first introduce the basic structures in optical waveguide devices.Then we propose and experimentally demonstrate optical interleavers,comb filter and optical switches based on silicon microresonators.The main research achievements of this thesis can be summarized as follows: 1.Optical interleavers based on silicon microresonatorsWavelength division multiplexing(WDM)and high spectral efficiency are two key methods to increase the capacity of an optical communication system.Optical interleaver can be used for(de)multiplexing of WDM signals,it provides functions such as suppressing channel crosstalk and noise.To achieve compact footprint and low power consumption,we propose and experimentally demonstrate three kinds of silicon photonic interleavers.1)Wavelength-tunable interleaver based on integrated Michelson-Gires-Tournois interferometer(MGTI): We propose and experimentally demonstrate a silicon photonic MGTI interleaver with compact footprint and boxlike transmission spectra.Compared to microring-based interleavers,the proposed device has a shorter cavity length and a higher tuning efficiency due to the standing-wave characteristic of the Gires-Tournois etalons(GTEs).The device footprint is 125 ?m × 376 ?m.The 20-to-3 dB bandwidth ratio is ~1.63.The thermal-tuning efficiency is ~0.02 nm/mW.2)Wavelength-tunable interleaver based on an interfering loop containing a Fabry-Perot resonator(FPR)formed by two Sagnac loops: We propose an interfering loop containing an FPR and design an interleaver with flattop passbands according to the maximally flat criterion.The interleaver features compact footprint,flattop passband,and easy tuning.The footprint is 120 ?m × 60 ?m.The 20-to-3 dB bandwidth ratio is ~1.42.The thermal-tuning efficiency is ~0.08 nm/mW.3)Coarse WDM(CWDM)interleaver based on an interfering loop containing a 1D FPR: We propose and demonstrate a flattop CWDM interleaver containing a 1D FPR with compact footprint and large FSR.The fabricated interleaver features compact footprint,large FSR,low insertion loss(IL),and flattop passband,which can be used to form CWDM multiplexers.The footprint is 64 ?m × 70 ?m.The IL is ~0.5 dB.The channel spacing is ~19 nm and the 1-dB bandwidth is ~13 nm.2.Wavelength and bandwidth-tunable optical filter based on silicon microresonatorsOptical signals with various channel spacings and bandwidths are existed in optical networks.To meet the dynamic changes of the networks,reconfigurable optical filters need to be designed.Wavelength and bandwidth tuning is an important topic in the design of reconfigurable optical filter.To achieve independent tuning of wavelength and bandwidth,we propose and experimentally demonstrate a tunable comb filter.Wavelength and bandwidth-tunable comb filter based on Sagnac loop reflectors(SLRs)with Mach-Zehnder interferometer(MZI)couplers: We propose and demonstrate a comb filter with tunable wavelength and bandwidth.The comb filter consists of two SLRs with MZI couplers.By thermally tuning the MZI couplers in common and differential modes,the phase shift and reflectivity of the SLRs can be changed,respectively,leading to tunable wavelength and bandwidth of the comb filter.The fabricated comb filter has 93 comb lines spaced by ~0.322 nm in a 30-nm wavelength range.The central wavelength can be red-shifted by ~0.462 nm with a tuning efficiency of ~0.019 nm/mW.A continuously tunable bandwidth from 5.88 GHz to 24.89 GHz is also achieved with a differential heating power ranging from 0.00 mW to 0.53 mW.3.Optical switches based on silicon microresonatorsLarge-scale optical switches are important components in optical networks.Optical switches based on silicon microresonators have compact footprint,low power consumption,and wavelength selectivity.We experimentally demonstrate two kinds of optical switches based on silicon microresonators.The structures of the switching elements(SEs)are dual-nanobeam MZI and dual-ring resonator,respectively.1)2 × 2 thermo-optic(TO)switch based on dual-nanobeam MZI: We experimentally demonstrate a 2 × 2 TO switch based on dual-nanobeam MZI,which is an MZI with embedded nanobeam cavity in each arm.Due to the ultra-small mode volume and high Q factor of the nanobeam cavities,2 × 2 switch with compact footprint and low power consumption can be realized.The footprint of the switch is 38 ?m × 84 ?m.The heating powers for the cross and bar states are ~2.66 mW and ~2.36 mW,respectively.The rising and falling times are 7.1 ?s and 3.9 ?s,respectively.2)N × N switches based on dual-ring resonator: We experimentally demonstrate a 2 × 2 TO switch,a 4 × 4 TO switch,and a 4 × 4 electro-optic(EO)switch.We also designed a 16 × 16 EO switch.In the EO SEs,integrated microheater,p-i-n junction,and photodetector(PD)are used for resonance wavelength alignment,EO switching,and power monitoring,respectively.The TO tuning efficiency of the dual-ring resonator is ~0.057 nm/mW.The TO tuning power for an FSR is ~210 mW.The EO tuning efficiency is ~0.034 nm/mW,the rising and falling times are 5.5 ns and 6.9 ns,respectively.The responsibility of the PD is ~0.53 A/W.The maximum IL of the 4 × 4 EO switch is 10.3 dB,the extinction ratio of EO tuning is 27.5 dB.