Abstract: The present invention provides an optical switch having a photonic crystal structure. An optical switch of the invention has a slab optical waveguide structure whose core (35) has a two-dimensional photonic crystal structure where two or more media (33, 34) with different refractive indices are alternately and regularly arranged in a two-dimensional manner. The photonic crystal structure comprises: a line-defect waveguide; and means for altering the refractive index of the line-defect waveguide.

Abstract: A microchip includes a clad layer having a channel through which a sample flows, and an optical waveguide formed within the clad layer and having a higher refractive index than the clad layer. The optical waveguide is formed to act on the channel optically. Thus, the sample flowing in the channel can be analyzed with high accuracy even in the microchip having a fine structure.

Abstract: A total reflection confinement waveguide is connected to the end face of a line defect portion in a photonic-crystal line-defect-waveguide to constitute a waveguide. The photonic-crystal line-defect-waveguide comprises photonic crystal holes, which are arranged in two groups of triangular lattices within a high-permittivity medium, and a line defect portion provided at the interface of the two groups. The width of the total reflection confinement waveguide is identical to or substantially identical to the width of the line defect portion.

Abstract: An optical wavelength demultiplexer includes an optical lens, a first-side waveguide and a plurality of second-side waveguide. The lens has a wave number distribution-surface having a section where an angular frequency is constant, and said section having a shape which generally represents at least a part of an ellipse or a circle; a medium allowing group-velocity directions toward an inside of the section to allow said medium to exhibit a lens effect; a finite thickness defined by a distance between two parallel planarized surfaces of the medium; a first focusing point at an inside position of the lens; and a second focusing point at an outside position of the lens. The first-side waveguide is positioned for incidence of a wavelength-multiplexed optical signal into the lens. The plurality of second-side waveguide is so aligned that terminals thereof are positioned at respective focusing points of respectively different-wavelength components included in the wavelength-multiplexed optical signal.

Abstract: The present invention provides a method of optical exposure to form a lattice pattern on a photo-resist, wherein at least two times of multiple exposure are carried out by use of different patterns.

Abstract: An optical wavelength demultiplexer includes an optical lens, a first-side waveguide and a plurality of second-side waveguide. The lens has a wave number distribution-surface having a section where an angular frequency is constant, and said section having a shape which generally represents at least a part of an ellipse or a circle; a medium allowing group-velocity directions toward an inside of the section to allow said medium to exhibit a lens effect; a finite thickness defined by a distance between two parallel planarized surfaces of the medium; a first focusing point at an inside position of the lens; and a second focusing point at an outside position of the lens. The first-side waveguide is positioned for incidence of a wavelength-multiplexed optical signal into the lens. The plurality of second-side waveguide is so aligned that terminals thereof are positioned at respective focusing points of respectively different-wavelength components included in the wavelength-multiplexed optical signal.

Abstract: A total reflection confinement waveguide is connected to the end face of a line defect portion in a photonic crystal line defect waveguide to constitute a waveguide. The photonic crystal line defect waveguide comprises photonic crystal holes, which are arranged in two groups of triangular lattices within a high-permittivity medium, and a line defect portion provided at the interface of the two groups. The width of the total reflection confinement waveguide is identical to or substantially identical to the width of the line defect portion.

Abstract: The present invention provides a method of optical exposure to form a lattice pattern on a photo-resist, wherein at least two times of multiple exposure are carried out by use of different patterns.

Abstract: A photonic crystal comprises a plurality of elongated elements formed of a first dielectric material and arranged in a two-dimensional periodic honeycomb lattice. A second dielectric material surrounds the elongated elements and extending between them. The second dielectric material defines between the elongated elements a plurality of spaces filled with a third dielectric material. The first dielectric material has permittivity that is greater than permittivity of the second dielectric material and permittivity of the third dielectric material.

Abstract: The present invention provides an optical switch having a photonic crystal structure.

Abstract: A photonic crystal comprises a plurality of elongated elements formed of a first dielectric material and arranged in a two-dimensional periodic honeycomb lattice. A second dielectric material surrounds the elongated elements and extending between them. The second dielectric material defines between the elongated elements a plurality of spaces filled with a third dielectric material. The first dielectric material has permittivity that is greater than permittivity of the second dielectric material and permittivity of the third dielectric material.

Abstract: A photonic crystal comprises a plurality of elongated elements formed of a first dielectric material and arranged in a two-dimensional periodic honeycomb lattice. A second dielectric material surrounds the elongated elements and extending between them. The a second dielectric material defines between the elongated elements a plurality of spaces filled with a third dielectric material. The first dielectric material has permittivity that is greater than permittivity of the second dielectric material and permittivity of the third dielectric material.

Abstract: There is provided a method of dry etching a nickel film formed on a substrate by means of plasma of an etching gas, wherein the etching gas includes at least one of CO and CO2 gases, and the substrate is designed to keep a temperature in the range of −25° C. to 40° C. both inclusive, while the substrate is being etched. For instance, the etching gas is a mixture gas including CO and CO2 gases, a mixture gas including CO, CO2 and H2 gases, or a mixture gas including CO and H2 gases. The above-mentioned method provides higher etching accuracy, higher etching rate, and less etching damage in a substrate.

Abstract: There is provided a method of dry etching a nickel film formed on a substrate by means of plasma of an etching gas, wherein the etching gas includes at least one of CO and CO.sub.2 gases, and the substrate is kept at a temperature in the range of -25.degree. C. to 40.degree. C. both inclusive, while the substrate is being etched. For instance, the etching gas is a mixture gas including CO and CO.sub.2 gases, a mixture gas including CO, CO.sub.2 and H.sub.2 gases, or a mixture gas including CO and H.sub.2 gases. The above-mentioned method provides higher etching accuracy, higher etching rate, and less etching damage in a substrate.

Abstract: A MESFET has a metallic laminate including WSi.sub.x, Ti, Pt and Au films and implementing gate, source and drain electrodes of the MESFET and interconnects therefor. The substrate of the MESFET is formed of a substrate body, a first semiconductor layer made of n.sup.+ -GaAs doped with Si at a concentration of 2.times.10.sup.18 atoms/cm.sup.3 and a second semiconductor layer made of n.sup.+ -InGaAs doped with Si at a concentration of 1.times.10.sup.19 atoms/cm.sup.3. The source and drain electrodes contact the second semiconductor layer in an ohmic contact while the gate electrode contacts the first semiconductor layer in a Schottky contact through a hole formed in the second semiconductor layer. A reduced number of steps in manufacture of the MESFET can be obtained, thereby reducing fabrication costs of the MESFET.

Abstract: A method for forming an electrode on a mesa structure of a semiconductor substrate. The method comprises the steps of: selectively forming an electrode on a predetermined area in a surface of the semiconductor substrate; and subjecting the substrate to a selective etching by use of the electrode as a mask to form a mesa structure on the substrate so that the mesa structure is self-aligned just under the electrode.