TECHNOLOGY FOCUS - ELECTRONICS - Preferred Component: A pair of electrodes (6a, 6b) connected to both ends or the periphery of the carbon nano-tube. The light sensor comprises fine semiconductor particles in electric contact with the carbon nano-tube. The carbon nano-tube is a multi-wall carbon nano-tube. A dispersion elimination layer (8) is formed at least on a portion of the substrate, where the carbon nano-tube is disposed. The dispersion elimination layer comprises a semiconductor super lattice layer. At least a portion of the carbon nano-tube is covered with a protective layer, which is a dielectric body. Preferred Dimension: The carbon nano-tube has a diameter of 0.3-100 nm; a length of 0.1-100 nm. A gap between the pair of electrodes has a length 1-100 mum. Preferred Property: A connection resistance value between the carbon nano-tube and an electrode connected to it, is at most10 MOMEGA. A frequency of the high speed optical pulse signals to be converted is 1-10 MHz. The wavelength of the high speed optical pulse signals to be converted is 1-2 mum. Preferred Method: Formation of a layer of fine semiconductor particles comprises vapor depositioning the layer of fine semiconductor particles. Disposing at least a carbon nano-tube comprises dispersing carbon nano-tubes in a liquid medium to provide a liquid dispersion; bridging the liquid dispersion between both of the electrodes; and applying high frequency waves between the two electrodes to evaporate the liquid medium and to arrange the carbon nano-tubes, in a perpendicular direction to the electrodes. A direct current voltage is applied between the electrodes to burn out materials in the carbon nano-tubes.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The fine semiconductor particles include indium arsenide, gallium arsenide, indium phosphide, indium antimonide, gallium nitride, indium nitride, or gallium indium nitride. Each of the pair of electrodes includes gold, platinum, silver, copper, tantalum, niobium, or titanium. The semiconductor super lattice layer comprises at least2 elements from gallium, arsenide, indium, or phosphide.