The Basic Application Of Fabrication Of Planar Optical Waveguide By UV Writing

With the rapid increase of global message volume, optical communicationsystem's demand for bandwidth and capacity improves constantly.Wavelength division multiplex technology is capable of realizing largecapacity and multifunction. It has great potential in network serviceapplication and becomes preferred technologh in optical fiber communication.Arrayed waveguide grating is considered as a kind of new promising devicedue to its low propagation loss, high wavelength resolution, easily coupledwith optical fiber. The components based on AWG represent one of the keyenabling technologies for DWDM systems.The arrayed waveguide grating consists of input/output waveguides, twofocusing slab regions and a phase-array of multiple channel waveguides withthe constant path length difference ?L between neighboring waveguides. It canwork as grating and complete the function of multiplexing and demultiplexingfor light with different wavelength. In this paper, we introduced the basicstructure and function of AWG, deduced the optical waveguide equations ofAWG in theory, summarized the studied progress and application of AWG, andformulized optimized means in performances of the phase error compensationand temperature error compensation and flat spectral response andbirefringence control of AWG. Single-mode channel waveguide is the basicelement of planar lightwave circuits and integrated lightwave devices. It's thefirst step of fabricating arrayed waveguides grating to prepare silica-on-siliconwaveguides.Silica-on-silicon planar waveguide technology has developed since 1990's,and more attention has been paid to silica waveguide on silicon because ofmature silicon processing technique and easy photoelectronic device'sintegration on a large scale. The preparation of silica-on-silicon waveguidematerials is always one of the hard and key steps to fabricate AWG devices.We are the first in China to fabricate 20μm-thickness and 0.1dB/cm-loss SiO2glass films and 5~40mol% Ge-doped silica waveguide material. We studiedemphatically the consolidation of SiO2 and Ge-doped SiO2, and discussed therelations of the refractive index, thickness and the annealing temperature.10mol% Ge-doped SiO2 is smooth and uniform after annealing at 1150℃for2h. It is suitable for core of waveguide with 5μm-thickness and smallroughness, 10-6 in the extinction coefficient. Its refractive index at 1550nm is1.4639, and its loss is less than 0.527dB/cm. In the experiment, we haveanalyzed the samples by SEM, AFM, XPS, XRD and VASE. It can beconcluded that we have fabricated smooth SiO2 and Ge-doped SiO2 glass film.This work is important in China for the research on silica-on-silicon planarwaveguide device, such as AWG. The effect of photoinduce refractive index changes in germanosilicate glassby UV writing has a potential advantage in integrated optical circuit andphotonics devices. We have studied the photosensitivity of germanosilicatethrough KrF excimer laser operating at 248nm. The relative refractive indexchange of 14mol% Ge-doped SiO2 film is 0.341% after exposure followed byhydrogen loading, which approaches to the reported results in this researchfield. We have obtained the dependence of irradiation time on the refractiveindex changes through a series of experiments. The positive and negativerefractive index change with the compact and dilation in volume has beenfound for different Ge concent. For high Ge content of 35mol%, the negativerelative refractive index change 0.234% and positive thickness change 3.96%has been obtained, which has verified "color center model"and "stress-reliefmodel"by theoretically analyzing. We also have discussed the defects in thefilm after hydrogen loading is GeO, which is quite benefit for us to improvephotosensitivity. The typical technology to fabricate AWG is to combine flame hydrolysisdeposition (FHD) or plasma enhanced chemical vapor deposition (PECVD)and reactive ion etching (RIE). But this technology has much shortcoming,such as the complicated processing step, the expensive cost, the shift of centerwavelength, the waveguide birefringence, and so on. The effect ofphotoinduced refractive index changes has been widely applied in fabricatingplanar waveguide devices and improving performance of typical RIE-etchedAWG. Based on these, we put forward to writing AWG device in silica planarwaveguide by UV writing, designed fabrication process and basic parameterand discussed some possible optimized means. We have designed andfabricated Cr-plating quartz amplitude mask used for exposure under KrFexcimer laser by ourselves, and successfully written planar waveguide gratingin SiO2 using this mask (1460mJ/cm2/pulse,6Hz,10min). We also havegroped the threshold of the energy density of this mask is 1530mJ/cm2/pulsefrom the damage of mask. And the AWG fabricated by UV writing will havemany good characteristics comparing with RIE technology, such as lowinsertion loss, polarization-insensitive, low cross-talk, precise centerwavelength, and so on. The basic content of this dissertation has embodied in some aspects asfollowed:(1) It is the first time to put forward to UV writing AWG optical waveguide devices in optical communication system using the effect of photoinduce refractive index changes in germanosilicate glass under UV light. Because the typical AWG etched process is more difficult, we can make use of the higher laser photon energy and induced UV light to fabricate AWG replacing typical etched technology, and this photon processing will obtain very high precision. This UV writing AWG technology is innovative.(2) It is the first for us in the country to fabricate SiO2 and Ge-doped SiO2 films on Si substrates using FHD and obtain smooth transparent thick glass after annealing treatment, the films thickness are more than 20μm and 6μm, respectively. The films have very low absorbed loss (<0.1dB/cm), have compact structure (the root-mean-square roughness of SiO2 is 0.184nm and 0.217nm for Ge-doped SiO2 film) and excellent optical properties (at 1550nm, the refractive index of SiO2 is 1.4513 and 14mol% Ge-doped SiO2 is 1.4678). They are entirely suitable for cladding and core of optical waveguide.(3) We use KrF excimer laser to irradiate the FHD-fabricated 14mol% Ge-doped SiO2 film (187mJ/cm2/pulse,10Hz),and the refractive index change at 1550nm after 10min irradiation reached 0.341%, which approaches to the reported results in this research field.(4) We have important breakthrough in mask fabrication technology. It is the first time to find applicable strong UV mask material, design and fabricate amplitude mask used for UV exposure by ourselves, choosing bar...