High Sensitivity Sensing And Nonlinear Frequency Doubling Research Of Symmetrical Metal-Cladding Waveguide

Optical waveguide is the basic and most important elements in integrated optic-electronics and guided wave optics,which have received the great attention from the academy community.At the same time optical waveguide technology got the rapid development in the fields of fundamental optics research,optics communication and integrated optics.In this paper,we present the sub-millimeter size symmetrical metal-cladding waveguide?SMCW?which works based on ultrahigh-order modes,developing from common dielectric plane waveguide,emphasize analyze the application of its high sensitivity on optical sensing,and the phase matching application of nonlinear second harmonic generation?SHG?based on the high mode density.The structure of symmetrical metal-cladding waveguide is simple,including the waveguide layer,the upper metal cladding layer and the lower metal cladding layer.Acting as the coupling layer the thickness of upper surface metal is thinner,which has a crucial influence on the waveguide coupling efficiency,and the lower surface metal is thicker which just devotes the refractive function.Because of the existence of the special modes whose effective refractive index is less than 1,the particular coupling technology can be used which we call as free space coupling technology.The light energy can be directly coupled into the waveguide from the free space when the phase matching condition was satisfied without using any coupling elements,such as,grating or prism.Free space coupling avoids the inconvenience in prism coupling and the difficulty of grating fabrication process which is a simple and convenient coupling method.Since the general metal has the negative coefficient of refractive index,the effective index of the existence modes could be close to zero.These modes have a small reflection angle in the interface of the guide layer and can experience more times resonances in the same transverse propagation distance.Thus some of different properties are exhibited,such as high sensitivity,polarization independence and so on.These properties provide the theoretical basis of our research.The main works completed in this paper are as follows:?1?According to the high sensitivity characteristic of ultrahigh-order modes in SMCW,the low concentration of epidermal growth factor receptor solution refractive index detection has been achieved.Cohen isolated an active substance that can stimulate the activity of nerve growth in a rat submandibular gland.He purified the single polypeptide composed of 53 amino acids in 1962 and called it as epidermal growth factor?EGF?.Subsequent studies found that EGF promotes cell proliferation in a variety tissues and plays an important role in the occurrence and development process of many tumors.Theoretical analysis shows that the UOMs excited in the HCMW have a highly sensitive response to the refractive index?RI?variation of the guiding layer.An EGFR solution with a 0.2ng/ml alteration was detected and the corresponding result was given.?2?The phase matching of nonlinear SHG was achieved by using SMCW.The nonlinear SMCW was structured by depositing silver?Ag?on the upper and lower surfaces of a lithium niobate?LiNbO₃?plate,which having a high degree of parallelism.LiNbO₃,possessing the high nonlinear coefficient and high resistance to damage threshold,is the ideal nonlinear crystal material and the related researches also received extensive attention.The phase matching method of SHG including angle phase and temperature phase matching,which have a strict requirement about angle and temperature of the incident light.In order to achieve a high efficiency SHG,it is necessary that the modes have the same effective index and a higher mode overlap ratio.Because of the high guided mode density,it is easily to achieve the mode phase matching for SMCW.