| CPC G01N 21/3504 (2013.01) [G01N 33/0027 (2013.01); G01N 2201/0635 (2013.01)] | 1 Claim |
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1. A mid-infrared gas sensor based on a tapered sub-wavelength grating slot waveguide, comprising a lower cladding, a first tapered grating array and a second tapered grating array, wherein
the lower cladding is a cuboid waveguide and is made of calcium fluoride, a length direction of the lower cladding is a left-right direction, a width direction of the lower cladding is a front-back direction, a thickness direction of the lower cladding is an up-down direction, the lower cladding has a thickness greater than or equal to 6 μm, the first tapered grating array and the second tapered grating array are disposed on an upper surface of the lower cladding, and the first tapered grating array is located in front of the second tapered grating array;
the first tapered grating array is formed by m identical first core waveguides that are regularly distributed at intervals from left to right, a value of m is 5566, the first core waveguides are tapered waveguides and are made of silicon, front faces of the first core waveguides are rectangular, long edges of the front faces of the first core waveguides are in the left-right direction, wide edges of the front faces of the first core waveguides are in the up-down direction, the long edges of the front faces of the first core waveguides have a length of 784 nm, the wide edges of the front faces of the first core waveguides have a width of 6 μm, long edges of rear faces of the first core waveguides are in the left-right direction, wide edges of the rear faces of the first core waveguides is in the up-down direction, the long edges of the rear faces of the first core waveguides have a length of 980 nm, the wide edges of the rear faces of the first core waveguides have a width of 6 μm, each first core waveguide has four sides, a distance between the front faces and the rear faces of the first core waveguides is 1.6 μm, an upper side and a lower side of each first core waveguide are both isosceles trapezoids with a upper base of 784 nm, a lower base of 980 nm and a height of 1.6 μm, left and right sides of the first core waveguides are rectangular, wide edges of the left and right sides of the first core waveguides are in the up-down direction and have a width of 6 μm, two long edges of the left side of each first core waveguide coincide with a left hypotenuse of the upper side of the first core waveguide and a left hypotenuse of the lower side of the first core waveguide in a one-to-one corresponding manner, two long edges of the right side of each first core waveguide coincide with a right hypotenuse of the upper side of the first core waveguide and a right hypotenuse of the lower side of the first core waveguide in a one-to-one corresponding manner, the front faces of the m first core waveguides are located on a same plane, the rear faces of the m first core waveguides are located on a same plane, the plane where the front faces of the m first core waveguides are located is parallel to a front face of the lower cladding, a distance from a bilateral symmetry plane of a leftmost first core waveguide of the m first core waveguides to a left face of the lower cladding is greater than or equal to 980 nm, a distance from a bilateral symmetry plane of a rightmost first core waveguide to a right face of the lower cladding is greater than or equal to 980 nm, and a distance between the bilateral symmetry planes of every two adjacent first core waveguides is 1960 nm;
the second tapered grating array is formed by m identical second core waveguides that are regularly distributed at intervals from left to right, the value of m is 5566, the second core waveguides are tapered waveguides and are made of silicon, rear faces of the second core waveguides are rectangular, long edges of the rear faces of the second core waveguides are in the left-right direction, wide edges of the rear faces of the second core waveguides are in the up-down direction, the long edges of the rear faces of the second core waveguides have a length of 784 nm, the wide edges of the rear faces of the second core waveguides have a width of 6 μm, long edges of front faces of the second core waveguides are in the left-right direction, wide edges of the front faces of the second core waveguides are in the up-down direction, the long edges of the front faces of the second core waveguides have a length of 980 nm, the wide edges of the front faces of the second core waveguides have a width of 6 μm, a distance between the front faces and the rear faces of the second core waveguides is 1.6 μm, each second core waveguide has four sides, an upper side and a lower side of each second core waveguide are both isosceles trapezoids with an upper base of 784 nm, a lower base of 980 nm and a height of 1.6 μm, left and right sides of the second core waveguides are rectangular, wide edges of the left and right sides of the second core waveguides are in the up-down direction and have a width of 6 μm, two long edges of the left side of each second core waveguide coincide with a left hypotenuse of the upper side of the second core waveguide and a left hypotenuse of the lower side of the second core waveguide in a one-to-one corresponding manner, two long edges of the right side of each second core waveguide coincide with a right hypotenuse of the upper side of the second core waveguide and a right hypotenuse of the lower side of the second core waveguide in a one-to-one corresponding manner, the front faces of the m second core waveguides are located on a same plane, the rear faces of the m second core waveguides are located on a same plane, the plane where the rear faces of the m second core waveguides are located is parallel to the rear face of the lower cladding, a distance from a bilateral symmetry plane of a leftmost second core waveguide of the m second core waveguides to the left face of the lower cladding is greater than or equal to 980 nm, a distance from a bilateral symmetry plane of a rightmost second core waveguide to the right face of the lower cladding is greater than or equal to 980 nm, and a distance between the bilateral symmetry planes of every two adjacent second core waveguides is 1960 nm;
a distance from the plane where the front faces of the m second core waveguides are located to the plane where the rear faces of the m first core waveguides are located is 120 nm; and
a distance from the plane where the front faces of the m first core waveguides are located to the front face of the lower cladding is equal to a distance from the plane where the rear faces of the m second core waveguides are located to the rear face of the lower cladding, and is greater than or equal to 11.55 μm.
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