Design,Fabrication And Characterization Of All-solid Photonic Bandgap Fiber

All-solid photonics bandgap fiber(AS-PBGF)has most of the prerequisites for high-power laser applications,including the all-solid configuration,large mode area,effective single-mode(SM)operation and selective wavelength filtering etc.It is considered as a promising candidate of large-mode-area fibers for suppressing the Stimulated Raman Scattering(SRS)and transverse mode instability simultaneously.Therefore,the design,fabrication and characterization of AS-PBGF are systematically investigated in this thesis,and the main contens are as follows:In terms of AS-PBGF structure design.We have proposed an SRS-free1-cell-core AS-PBGF design with strict SM property and a modified structure scheme called leakage channels enabled multi-resonant AS-PBGF(LC-PBGF).The proposed LC-PBGF structure exhibits bending-resistant and robust SM performance,which shows no sensitivity to the arbitrary bending directions.In addition,some derivative structures based on LC-PBGF concept have also been proved to have great potential for low loss and SM operation.In terms of AS-PBGF fabrication.Based on the stack-and-draw method,we have successfully fabricated two multi-resonant AS-PBGF samples,one of which has a broadband transmission region around 1μm waveband(Fiber#1),and another sample is cautiously drawn to achieve the SRS suppression(Fiber#2).Both the two fibers are realized in great agreement with the theoretical model.In terms of AS-PBGF characterization.The working bandwidth of Fiber#1 is measured to be over 200 nm,and bending loss lower than 0.1 d B/m is obtained within the signal waveband.By employing the modal decomposition technique,the output profile of Fiber#1 is demonstrated to be almost strict SM performance.In addition,we also report the abnormal variation of M~2 even if the SM operation is guaranteed,which is actually the first demonstration of this phenomenon to our knowledge.Bending loss of Fiber#2 is measured to be lower than 0.05 d B/m within the signal waveband,and the transmission spectrum indicates a first-order SRS suppression ratio larger than 15 d B,which proclaims a great prospect for long-distance high-power delivery.In terms of beam propagation property.We firstly reveal the spectrally U-shaped profile of beam propagation factor in AS-PBGF and further extend the general applicability of this finding in AS-PBGF field.This finding seems essential to instruct a scheme for maintaining the beam quality factor M~2 while optimizing the SM behavior of AS-PBGF,and is expected to be extended to other bandgap-guided fibers.