Patent ID: 8282882

Claim:
An apparatus for on-chip optical absorption spectroscopy comprising: a substrate; a bottom cladding disposed on the substrate; a slab disposed on the bottom cladding, wherein the refractive index of the bottom cladding is lower than the refractive index of the slab; a plurality of void columnar members etched through the slab, wherein the plurality of void columnar members form a periodic lattice with a lattice constant α; a core in the slab comprising an input side on a first end of the slab and an output side on a second end of the slab; a photonic crystal slot waveguide comprising: a photonic crystal waveguide formed within the core by a row of void columnar members from the input side to the output side, wherein the row of void columnar members is filled with the material of the slab; and one or more slot waveguides defined by one or more void slots within the photonic crystal waveguide, extending the entire length of the photonic crystal waveguide; an input impedance taper in the photonic crystal waveguide at the input side of the photonic crystal waveguide in the plane of the slab, wherein the input impedance taper is formed by one or more void columnar members from the input side shifted away and normal to the photonic crystal waveguide and adjacent the length of both sides of the photonic crystal waveguide; an input ridge waveguide in the core coupled to the input impedance taper in the photonic crystal waveguide, in the plane of the slab; an output impedance taper in the photonic crystal waveguide at the output side in the plane of the slab, wherein the output impedance taper is formed by one or more void columnar members from the output side shifted away and normal to the photonic crystal waveguide and adjacent the length of both sides of the photonic crystal waveguide; an output ridge waveguide in the core coupled to the output impedance taper in the photonic crystal waveguide, in the plane of the slab; the one or more void slots within the photonic crystal slot waveguide extend into the input impedance taper, the input ridge waveguide, the output impedance taper, and the output ridge waveguide; wherein the photonic crystal slot waveguide supports one or more guided modes and further comprises a region where the electric field intensity of a guided light is enhanced and the group velocity of the guided light is lowered; and wherein the output transmission spectrum intensity of the guided light varies as a function of the absorbance of an analyte within the photonic crystal slot waveguide.