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Applications Of Waveguide Bragg Gratings In Si-and InP-based Photonic Integrated Circuits

Posted on:2020-12-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:R L XiaoFull Text:PDF
GTID:1488305774973929Subject:Optical Engineering
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Photonics are the investigation of light emission,transmission,modulation,etc.With the advanced investigation,technologies about light generation,detection,and manipulation have been greatly improved.Recently,photonic integrated circuits(PICs)have attracted great interests owing to its potential for the next-generation optical communication and sensing.PIC is a complex integrated circuit that forms a single photonic circuit by incorporation of multiple stand-alone optical devices.Due the high integration density of PICs,advantages such as compact size,low power consumption and cost effective can be achieved.Currently,PIC fabrication is mainly based on silicon(Si),indium phosphide(InP),silicon nitride(Si3N4),etc.Fiber Bragg gratings(FBGs)have been widely studied and used in optical communication,sensing,and signal processing.FBGs can achieve abundant light responses with proper design of the grating parameters,such as the period,phase,effective refractive index,and grating strength.Various FBG-based photonic devices have been extensively investigated in the past few decades,such as narrow-band filters,interleavers,add/drop multiplexers,and dispersion compensators.Alternatively,waveguide Bragg gratings(WBGs)can offer the similar performance and function with FBGs in optical waveguide.Specifically,WBGs are equivalent to integrated FBGs,and are the key filter and resonated structures for PICs.In this work,we propose several novel optical devices based on the research of Siand InP-based optical chips,and optimize several existing devices.In the Si-based PICs,we studied a new-type of WBG—the transversely modulated WBG(TM-WBG),which can manipulate the guided modes on chip and provide abundant filtering responses.Two devices based on the TM-WBGs are proposed and studied via simulation and experiment.(a)We propose a WBG filter with reflection light dropped in a silicon-on-insulator platform.Most of the light reflected by the WBG is coupled to a branch waveguide,while some residual reflected light radiates rather than propagating back to the input port.The proposed structure is expected to aid practical applications of WBGs to various photonic integrated devices.(b)We propose an on-chip mode converter via two cascaded Bragg reflection processes.The forward conversion between two guided modes can be achieved with the aid of an additional mode.The proposed method may pave a new path for the mode converters with desired conversion spectrum.In the InP-based PICs,we studied a new-type waveguide sampled Bragg grating(WSBG)based on the reconstruction equivalent chirp(REC)technique.Several devices are studied by theoretical analysis and experiment,including tunable semiconductor lasers(TSLs)and multiwavelength laser arrays(MLAs).(a)We propose four types of wide-band TSLs based on the WSBGs.Multi-wavelength distributed feedback(DFB)lasers are arranged in matrix and integrated with an active combiner and a semiconductor optical amplifier(SOA).Wide-band TSLs are fabricated and measured via the 2-by-2,4by-1,2-by-4,and 4-by-4 matrix-arrangements.Tuning range of 12,24,and 44 channels with 100 GHz spacing are realized.(b)We propose three types of narrow-band TSLs based on the high-wavelength-precision and flexibility of the REC technique,including one type of paralleled MLA and two types of in-series MLAs.(c)We present the finding that periodic structural defects(PSDs)along a WBG can shift the Bragg wavelength,which will be a benefit for MLAs.(d)A new effect of transient mode competition in directly modulated DFB laser based on WSBG is presented and studied.
Keywords/Search Tags:Photonic integrated circuit, Waveguide Bragg grating, On-chip optical filter, On-chip mode converter, Sampled Bragg gratings, Tunable semiconductor laser, Multiwavelength laser array, Direct-modulated laser
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