There is provided a sensing chip capable of measuring a refractive index by utilizing a long-range surface plasmon polariton, accurately measuring an accumulative refractive index in a wide range, and more easily enabling sealing for measurement. The present invention relates to the sensing chip which has a thin metal film or a strip-like metal grown on an underlayer, and has a dielectric that limits a refractive index and a dielectric buffer layer on an upper surface and a lower surface of the thin metal film or the strip-like metal. The dielectric buffer layer is attached onto the thin metal film or the strip-like metal. The thin metal film or the strip-like metal and the buffer layer are sandwiched between two dielectric layers. A hole is made in a surface of the upper dielectric layer to serve as a measurement groove.
1. A sensing chip for measuring a refractive index of a long-range surface plasmon polariton, having a thin metal film or a strip-like metal as well as an upper limiting layer and a lower limiting layer made of silicon-rich silica SiO x (where 0<x<2), SiO 2 or benzocyclobutene (BCB) and a dielectric buffer layer formed on the upper and lower surfaces thereof, wherein
said dielectric buffer layer is made of silicon-rich silica SiO x (where 0<x<2) or silicon nitride SiN y (where 0<y<4/3), and attached onto a measurement groove of the metal thin film or the strip-like metal,
the metal thin film or the strip-like metal and the buffer layer are sandwiched between said upper limiting layer and said lower limiting layer, and
the upper layer surface of said upper limiting layer made of SiO x , SiO 2 or benzocyclobutene is perforated to form the measurement groove,
all of the aforementioned structures are grown on an Si underlayer, a GaAs underlayer, an InP underlayer or an SiO 2 underlayer, and
the sensing chip is arranged so that the refractive index of a long-range surface plasmon polariton is measured by forming a long-range surface plasmon polariton by performing excitation on an end face of said metal thin film or said strip-like metal, and measuring a refractive index change of a liquid in the measurement groove or an antigen-antibody reaction of an organism from a change in transmission loss of said long-range surface plasmon polariton and/or a change in a light spot size.
2. The sensing chip according to claim 1 , wherein the metal in said metal thin film or said strip-like metal is any one of gold, silver, aluminum, copper, titanium, nickel and chromium, the thickness of the metal thin film is 1 nm to 100 nm, and the width of the strip-like metal is 50 nm to 100 μm.
3. The sensing chip according to claim 1 , wherein said upper limiting layer and said lower limiting layer are dielectrics, the refractive indices thereof are 1.0 to 4.0, and the thicknesses of these dielectrics are 1 to 10000 nm.
4. The sensing chip according to claim 1 , wherein said dielectric buffer layer is made of SiO x (where 0<x<2) or SiN y (where 0<y<4/3), the refractive index thereof is 1.0 to 4.0, and the thickness of this dielectric is 1 to 10000 nm.
5. The sensing chip according to claim 1 , wherein the thickness of said upper limiting layer or said lower limiting layer made of SiO 2 is 1 μm, and the thickness of said upper limiting layer or said lower limiting layer made of benzocyclobutene is larger than 1 μm.
6. The sensing chip according to claim 1 , wherein a bio material is fixed onto the dielectric buffer layer in the measurement groove.