Abstract: An infrared detector includes a semiconductor substrate, a first contact layer formed on the semiconductor substrate, a light-absorbing layer formed on the first contact layer, a second contact layer formed on the light-absorbing layer, and a voltage source that applies a voltage between the first contact layer and the second contact layer. The light-absorbing layer includes at least a part in which a first intermediate layer, a quantum dot layer, a second intermediate layer, a current block layer, a third intermediate layer, and an electron-doped layer are stacked in this order. The energy at a bottom of a conduction band in the current block layer is larger than the energy at a bottom of a conduction band in the intermediate layer and the thickness of the first intermediate layer is larger than the thickness of the third intermediate layer.

Abstract: An infrared detector includes a semiconductor substrate, a first contact layer formed on the semiconductor substrate, a light-absorbing layer formed on the first contact layer, a second contact layer formed on the light-absorbing layer, and a voltage source that applies a voltage between the first contact layer and the second contact layer. The light-absorbing layer includes at least a part in which a first intermediate layer, a quantum dot layer, a second intermediate layer, a current block layer, a third intermediate layer, and an electron-doped layer are stacked in this order. The energy at a bottom of a conduction band in the current block layer is larger than the energy at a bottom of a conduction band in the intermediate layer and the thickness of the first intermediate layer is larger than the thickness of the third intermediate layer. It is therefore possible to provide an infrared detector having a high signal to noise ratio.

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 one-dimensional photonic crystal has a spatial distribution in which the refractive index periodically varies in a first direction that light is caused to be propagated and in which the refractive index is uniform in a second direction perpendicular to the first direction. An antireflective coating structure for the one-dimensional photonic crystal includes a thin-film having a refractive index and a thickness determined by a predetermined calculation method. A two or three-dimensional photonic crystal comprises two or more media that have different refractive indexes and are arranged in a two or three-dimensional pattern. An antireflective coating structure for the two or three-dimensional photonic crystal includes a thin-film comprising one of the media included in the photonic crystal. In the structure, the thin-film is disposed on an end face of the photonic crystal so as to increase the incident efficiency of light entering the photonic crystal.

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: 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 one-dimensional photonic crystal has a spatial distribution in which the refractive index periodically varies in a first direction that light is caused to be propagated and in which the refractive index is uniform in a second direction perpendicular to the first direction. An antireflective coating structure for the one-dimensional photonic crystal includes a thin-film having a refractive index and a thickness determined by a predetermined calculation method. A two or three-dimensional photonic crystal comprises two or more media that have different refractive indexes and are arranged in a two or three-dimensional pattern. An antireflective coating structure for the two or three-dimensional photonic crystal includes a thin-film comprising one of the media included in the photonic crystal. In the structure, the thin-film is disposed on an end face of the photonic crystal so as to increase the incident efficiency of light entering the photonic crystal.

Abstract: A method for measuring the waveform of light is provided, which makes it possible to synchronize easily the phase of sampling light with the phase of target light even if the target light is ultra-high speed pulsed light and is transmitted by way of long transmission channel, and to measure the waveform of target light with sufficient time resolution in real time. The method comprises the steps of: (a) generating sampling light having a pulse width sufficiently narrower than that of the target light from the target light; a repetition frequency of the sampling light having a constant difference with respect to a repetition frequency of the target light; (b) supplying the sampling light and the target light to a nonlinear optical member to generate cross-correlated light between the sampling light and the target light; and (c) measuring waveform of the target light based on the cross-correlated light.

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

Abstract: A method for measuring the waveform of light is provided, which makes it possible to synchronize easily the phase of sampling light with the phase of target light even if the target light is ultra-high speed pulsed light and is transmitted by way of long transmission channel, and to measure the waveform of target light with sufficient time resolution in real time. The method comprises the steps of: (a) generating sampling light having a pulse width sufficiently narrower than that of the target light from the target light; a repetition frequency of the sampling light having a constant difference with respect to a repetition frequency of the target light; (b) supplying the sampling light and the target light to a nonlinear optical member to generate cross-correlated light between the sampling light and the target light; and (c) measuring waveform of the target light based on the cross-correlated light.