Abstract: Disclosed is a polarized light generating device based on an optical waveguide, which includes first to fourth input optical waveguides, respectively, for receiving input light from an outside, first to fifth optical splitters configured to receive at least one light and output the received at least one light as at least one light, and an optical converter configured to receive at least one light from the fifth optical splitter and convert the received light to generate polarized light. The polarized light generating device receives the input light through one of the first to fourth input optical waveguides, and generates a first polarized light, a second polarized light, a third polarized light, and a fourth polarized light. The first to fourth polarized lights belong to elements of two arbitrary two-dimensional mutually unbiased basis sets.

Abstract: Provided is a polarization decomposition device. The polarization decomposition device includes a polarization beam splitter configured to split an optical signal into a first polarized light having a first polarization direction and a second polarized light having a second polarization direction different from the first polarized light, a phase shifter configured to delay a phase of the first polarized light, a polarization rotator configured to rotate the second polarized light so that the polarization direction of the second polarized light is changed, and an interference beam splitter configured to allow the first polarized light in which the phase is delayed and the second polarized light in which the polarization direction is rotated to interfere with each other and split them into a third polarized light and a fourth polarized light.

Abstract: Provided are a beam tracking module, a free-space quantum communication device, and a free-space optical communication device. The beam tracking module for free-space quantum communication includes a controller configured to determine a divergence angle of a reference beam on the basis of divergence angle control data, a beam path control optical part configured to output the reference beam, and a beam transmitter configured to adjust the divergence angle through the beam path control optical part so that the reference beam having the determined divergence angle is output.

Abstract: Disclosed is a quantum key distribution system using an RFI (reference frame independent) QKD (quantum key distribution) protocol, which includes a first signal processing circuit that generates transmission basis information and transmission bit information, a quantum channel transmitter that generates a single photon or coherent light, and modulates the single photon or the coherent light based on the transmission basis information and the transmission bit information to generate a quantum signal, a quantum channel receiver that receives the quantum signal through a quantum channel and detects reception bit information from the quantum signal based on reception basis information, and a second signal processing circuit that generates the reception basis information, transmits the reception basis information to the first signal processing circuit through a public channel, and receives the transmission basis information from the first signal processing circuit through the public channel.

Abstract: A quantum key distribution system using an RFI (reference frame independent) QKD (quantum key distribution) protocol includes a quantum channel transmitter that generates a first quantum signal including quantum information and provides the first quantum signal to an external device through a quantum channel, a first public channel transceiver that generates an optical signal including first additional information related to a QKD operation, and transmits and receives the optical signal through a public channel, a second public channel transceiver that receives the optical signal through the public channel and generates a measurement result by measuring a circular polarization component of the optical signal, and a quantum channel receiver that receives the first quantum signal through the quantum channel, generates a second quantum signal by correcting a polarization distortion of the first quantum signal based on the measurement result, and demodulates the quantum information from the second quantum signal.

Abstract: An optical alignment device according to an embodiment of the inventive concept includes an optical alignment plate having a first hole and at least one second hole, in which the first hole and the second hole pass through the optical alignment plate, and an optical detection element disposed on the optical alignment plate. Here, the optical detection element includes a substrate having a first surface and a second surface, which face each other, a lens disposed on the first surface, and an optical sensor disposed on the second surface, and the optical detection element vertically overlaps the first hole and the second hole. The lens is exposed to the outside by the first hole, and the second hole is connected with a vacuum suction unit to fix the optical detection element to the optical alignment plate.

Abstract: Disclosed are a quantum information transmitter, a quantum communication system including the same, and an operating method of the quantum information transmitter. The quantum information transmitter includes a light source driver, a light source, and a light modulator. The light source driver generates a first light source driving signal having a first level and a second light source driving signal having a second level. The light source generates a first light signal having a first average number of photons in response to the first light source driving signal, and generates a second light signal having a second average number of photons in response to the second light source driving signal. The optical modulator modulates the first light signal to generate a target signal, and modulates the second light signal to generate a decoy signal.

Abstract: Provided is a waveguide photodetector including a semiconductor substrate, a first optical waveguide and a second optical waveguide, which are sequentially laminated on the semiconductor substrate, in which each of the first optical waveguide and the second optical waveguide includes a first portion and a second portion, and the first portion extends from the second portion in a first direction parallel to a top surface of the semiconductor substrate, a refractive index matching layer disposed on the second portion of the second optical waveguide, a clad layer disposed on the refractive index matching layer, and an absorber disposed between the refractive index matching layer and the clad layer. Here, the second optical waveguide has a first conductive-type, the clad layer has a second conductive-type opposite to the first conductive-type, and the refractive index matching layer includes a first semiconductor layer that is an intrinsic semiconductor layer.

Abstract: Disclosed is a quantum key distribution system using an RFI (reference frame independent) QKD (quantum key distribution) protocol, which includes a first signal processing circuit that generates transmission basis information and transmission bit information, a quantum channel transmitter that generates a single photon or coherent light, and modulates the single photon or the coherent light based on the transmission basis information and the transmission bit information to generate a quantum signal, a quantum channel receiver that receives the quantum signal through a quantum channel and detects reception bit information from the quantum signal based on reception basis information, and a second signal processing circuit that generates the reception basis information, transmits the reception basis information to the first signal processing circuit through a public channel, and receives the transmission basis information from the first signal processing circuit through the public channel.

Abstract: Provided is a light modulation device includes a substrate, a lower clad layer disposed on the substrate, a core layer disposed on the lower clad layer to extend in a first direction which is parallel to a top surface of the substrate, and an upper clad layer covering the core on the lower clad layer. The core layer includes a waveguide layer extending in the first direction; and photonic crystal structures disposed in the waveguide layer and periodically arranged along the first direction.

Abstract: Disclosed are a quantum information transmitter, a quantum communication system including the same, and an operating method of the quantum information transmitter. The quantum information transmitter includes a light source driver, a light source, and a light modulator. The light source driver generates a first light source driving signal having a first level and a second light source driving signal having a second level. The light source generates a first light signal having a first average number of photons in response to the first light source driving signal, and generates a second light signal having a second average number of photons in response to the second light source driving signal. The optical modulator modulates the first light signal to generate a target signal, and modulates the second light signal to generate a decoy signal.

Abstract: Provided is a waveguide photodetector including a semiconductor substrate, a first optical waveguide and a second optical waveguide, which are sequentially laminated on the semiconductor substrate, in which each of the first optical waveguide and the second optical waveguide includes a first portion and a second portion, and the first portion extends from the second portion in a first direction parallel to a top surface of the semiconductor substrate, a refractive index matching layer disposed on the second portion of the second optical waveguide, a clad layer disposed on the refractive index matching layer, and an absorber disposed between the refractive index matching layer and the clad layer. Here, the second optical waveguide has a first conductive-type, the clad layer has a second conductive-type opposite to the first conductive-type, and the refractive index matching layer includes a first semiconductor layer that is an intrinsic semiconductor layer.

Abstract: Provided is a polarization decomposition device. The polarization decomposition device includes a polarization beam splitter configured to split an optical signal into a first polarized light having a first polarization direction and a second polarized light having a second polarization direction different from the first polarized light, a phase shifter configured to delay a phase of the first polarized light, a polarization rotator configured to rotate the second polarized light so that the polarization direction of the second polarized light is changed, and an interference beam splitter configured to allow the first polarized light in which the phase is delayed and the second polarized light in which the polarization direction is rotated to interfere with each other and split them into a third polarized light and a fourth polarized light.

Abstract: Provided is an apparatus configured to split light into a plurality of polarizations, the apparatus including an input waveguide configured to receive the light, a first interferometer configured to split the light into a first polarization and a second polarization, and a second interferometer configured to split the light into a third polarization and a fourth polarization, wherein the first interferometer and the second interferometer are connected in parallel, the first interferometer comprises a first output waveguide configured to output the first polarization, and a second output waveguide configured to output the second polarization, and the second interferometer comprises a third output waveguide configured to output the third polarization, and a fourth output waveguide configured to output the fourth polarization.

Abstract: There is provided a receiver optical module including a photodetector having a plurality of channels, a capacitor disposing block formed on an upper portion of the photodetector, a plurality of capacitors formed on the capacitor disposing block, and an electrical wiring configured to connect the plurality of capacitors to electrodes of a plurality of channels of the photodetector, wherein the plurality of capacitors are formed on the capacitor disposing block such that distance between the capacitors and the electrodes of the corresponding channels are the same. Distortion and loss of signal characteristics of high frequency can be reduced and quality of a signal can be enhanced.

Abstract: Disclosed is a blend prepared by mixing a prepolymer and a vinyl monomer, wherein the prepolymer is prepared by a condensation reaction between a first compound represented by the formula Ar—H, where Ar comprises (a) a crosslinkable moiety at one end, (b) a moiety selected from the group consisting of —O—, —S—, —COO—, —CO—, —COS—, —SO2—, and —NH—, and (c) one or two repeating units selected from the group consisting of: where A is carbon or nitrogen, and X is hydrogen or halogen; and a second compound consisting of an aromatic moiety. Additionally disclosed is a polymer sheet that is a crosslinked product composed of the blend.

Abstract: A multiple output quantum random number generator coherently measures an optical source noise and outputs a random number sequence based on the independent and coherent measurement of optical source noise. Therefore, it is possible to output a random number sequence at a high speed and to perform multiple outputs.

Abstract: There is provided a receiver optical module including a photodetector having a plurality of channels, a capacitor disposing block formed on an upper portion of the photodetector, a plurality of capacitors formed on the capacitor disposing block, and an electrical wiring configured to connect the plurality of capacitors to electrodes of a plurality of channels of the photodetector, wherein the plurality of capacitors are formed on the capacitor disposing block such that distance between the capacitors and the electrodes of the corresponding channels are the same. Distortion and loss of signal characteristics of high frequency can be reduced and quality of a signal can be enhanced.

Abstract: A multiple output quantum random number generator coherently measures an optical source noise and outputs a random number sequence based on the independent and coherent measurement of optical source noise. Therefore, it is possible to output a random number sequence at a high speed and to perform multiple outputs.

Abstract: Disclosed are a method and an apparatus for transmitting and receiving coherent optical OFDM.