Abstract: A device for measuring half-wave voltage includes a light source that outputs an input optical signal, a beam splitter that separates the input optical signal into a first optical signal and a second optical signal and generates an interference signal based on the first optical signal and the second optical signal, a plurality of polarization controllers that adjust polarization states of optical signals, a phase modulator that adjusts a phase of the second optical signal based on an input voltage, a polarization beam splitter that determines propagation directions of the first optical signal and the second optical signal, a Faraday mirror that reflects by converting the polarization states of the optical signals output from the polarization beam splitter, and an optical detector that detects the interference signal and measures the half-wave voltage of the phase modulator based on the detected interference signal.

Abstract: Provided is an optical array device including a substrate, an optical waveguide input section extending in a first direction on the substrate, a cladding surrounding the optical waveguide input section and separating the substrate and the optical waveguide input section from each other on the substrate, and a stray light blocking pattern covering the cladding, wherein a lowermost surface of the stray light blocking pattern may be located at a lower level than a lowermost surface of the optical waveguide input section.

Abstract: Provided is an optical waveguide including a substrate, a lower cladding layer on the substrate, the lower cladding layer having a protrusion portion protruding in a first direction perpendicular to an upper surface of the substrate, a first core layer on the protrusion portion of the lower cladding layer, and an upper cladding layer conformally covering the first core layer and the lower cladding layer on the lower cladding layer. The upper cladding layer may have a thickness of 0.05 ?m to 0.5 ?m.

Abstract: Provided are an optical alignment device and an optical alignment method. The optical alignment device includes an input optical fiber, a light source provided at one terminal of the input optical fiber to generate input light, an input stage provided at another terminal of the input optical fiber, an output stage spaced apart from the input stage, a stage driving control unit configured to control driving of the input and output stages, a camera configured to receive output light generated from the input light by the waveguide chip and detect a waveguide mode, an output optical fiber having one terminal connected to the output stage, an optical power meter configured to detect an intensity of the output light, and a system controller configured to determine the waveguide mode and the intensity of the output light.

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: 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 herein is a semiconductor light emitting device capable of increasing the light extraction efficiency and a fabricating method thereof, the device including a buffer layer formed on a substrate; an n-type semiconductor layer formed on the buffer; an active layer formed on a partial area of the n-type semiconductor layer such that the n-type semiconductor layer is exposed; a p-type semiconductor layer formed on the active layer; a transparent conductive layer formed on the p-type semiconductor layer; a first mesa surface formed along a side wall of the active layer from a side wall of the transparent conductive layer; a passivation layer formed along the first mesa surface; and a metal reflectance film formed along the passivation layer such that it re-reflects escaping light, thereby re-reflecting escaping light to increase the light extraction efficiency.