Silicon Photonic Devices For On-Chip Multiplexing

With the development of the modern Internet of things(IoT),big data and other industries,the human society's demand for information is growing rapidly.The optical communication and optical interconencts are facing major challenges for the huge bandwidth requirements.Optoelectronic integrated devices have the advantages of small size,light weight and low power consumption(SWaP),which are considered to have the potential to break through the bottleneck.The silicon-based photonic devices have the characteristics of CMOS-compatibility and can be integrated with the ASIC chips.The prominent advantage of low cost has attracted much attention.Silicon on-chip multiplexing technology provides a possilbe way for high capacity optical communication/interconents.However,there are still lots of issues to be solved such as the high performance devices,polarization sensitivity,and temperature sensitivity.In this thesis,we mainly focus on the developing of several silicon photonic devices for on-chip multip lexing.Firstly,several kinds of silicon photonic devices for wavelength division multiplexing(WDM)have been investigated.Based on the multimode interference(MMI)coupler structure,two kinds of triplexers are demonstrated:One is based on the tilted MMI coupler and the other is based on the MMI coupler combined with the Bragg grating reflector.The experimental results show that the insertion losses are<2 dB and the crosstalks are<-15 dB,and also a large bandwidth more than 100 nm at 1310 nm band.The lengths of the devices are?450 ?m and are reduced by half compared with the device based on conventional MMI couplers.To further reduce the footprints and insertion loss,we propose a triplexer based on cascaded bent directional couplers(BDC),the footprint is significantly reduced to 19 ?m×31?m.The fabricated device is characterized with insertion loss of<1 dB and crosstalk of<-15 dB.The bandwidths of all output ports satisfy the communication standards.We also realized a wavelength division multiplexer based on contra-directional couplers with subwavelength grating waveguides.The size of the device is significantly reduced and the transmission spectra are flat-top,the 1 dB bandwidths of which are?11nm.Secondly,we focus on the investigations of the polarization sensitivity and temperature sensitivity for silicon photonic devices.A polarization insensitive diplexer based on cascaded BDC is demonstrated.The polarization dependent loss is<1 dB and the crosstalk is<-15 dB within the 35 nm bandwidth.Furthermore,the polarization-insensitive silicon waveguide crossings have been demonstrated,which can be used for large-scale integrated multiplexing system.The characterized device is with polarization dependent loss of<1dB and the crosstalk is<-25 dB within 90 nm bandwidth.We also design a polarization insensitive optical switch based on the Mach-Zender interferometer(MZI).The optimized polarization insensitive power spiltter ensures the performance of high extinction ratio.The extinction ratio is larger than 20 dB in the bandwidth of 100 nm.Additionally,we investigate the temparature sensitivity for a silicon optical filter.Based on the slot waveguide and the Bragg gratings with edge modulation,we propose and experimentally demonstrate a temperature insensitive narrow-band filter.The fabricated optical filter is with the bandwidth of 0.75 nm The wavelength shift of silicon optical filter is significantly suppressed by utilizing the cladding temperature compensation materials.The wavelength drift coefficient is less than-3pm/?,which can expand the operating temperature range of narrow-band optical filters.Finally,we summarize the work done in this thesis and look forward to the future work.