Silicon photonic spectrometer with multiple customized wavelength bands

A silicon photonic spectrometer with multiple customized wavelength bands is developed by introducing multiple channels of wideband optical filters based on multimode waveguide gratings(MWGs)for pre-filtering and the corresponding thermally tunable narrowband filter for high resolution.For these multiple customized wavelength bands,the central wavelengths,bandwidths,and resolutions are designed flexibly as desired,so that the system is simplified and the footprint is minimized for several practical applications(e.g.,gas sensing).A customized silicon photonic spectrometer is designed and demonstrated experimentally with four wavelength bands centered around1310 nm,1560 nm,1570 nm,and 1930 nm,which is,to the best of our knowledge,the first on-chip spectrometer available for sensing multiple gas components like HF,CO,H_(2)S,and CO_(2).The spectral resolutions of the four wavelength bands are 0.11 nm,0.08 nm,0.08 nm,and 0.37 nm,respectively.Such a customized silicon photonic spectrometer shows great potential for various applications,including gas monitors,wearable biosensors,and portable spectral-domain optical coherence tomography.

Reconfigurable optical add-drop multiplexers for hybrid mode-/wavelength-division-multiplexing systems

Dealing with the increase in data workloads and network complexity requires efficient selective manipulation of any channels in hybrid mode-/wavelength-division multiplexing(MDM/WDM)systems.A reconfigurable optical add-drop multiplexer(ROADM)using special modal field redistribution is proposed and demonstrated to enable the selective access of any mode-/wavelength-channels.With the assistance of the subwavelength grating structures,the launched modes are redistributed to be the supermodes localized at different regions of the multimode bus waveguide.Microring resonators are placed at the corresponding side of the bus waveguide to have specific evanescent coupling of the redistributed supermodes,so that any mode-/wavelength-channel can be added/dropped by thermally tuning the resonant wavelength.As an example,a ROADM for the case with three mode-channels is designed with low excess losses of<0.6,0.7,and 1.3 dB as well as low cross talks of<−26.3,−28.5,and−39.3 dB for the TE0,TE1,and TE2 modes,respectively,around the central wavelength of 1550 nm.The data transmission of 30 Gbps∕channel is also demonstrated successfully.The present ROADM provides a promising route for data switching/routing in hybrid MDM/WDM systems.