Abstract: The present disclosure relates to a planar optical waveguide element, and more particularly, to an optical waveguide end structure for effective optical signal connection with a light source, a light receiving element, or a different type of optical waveguide element. According to an exemplary embodiment of the present disclosure, there is disclosed an optical waveguide structure, including: a planar optical waveguide including a lower clad, a waveguide core formed on the lower clad, and a clad layer formed on the waveguide core; and an optical lens formed on a surface of the clad layer. One end of the optical waveguide forms an inclined surface having a predetermined inclination angle.

Abstract: An illuminating unit and a display apparatus including the illuminating unit are provided. The illuminating unit generates and emits light to a display element of the display apparatus, and includes a light source; a uniformizing unit which uniformizes light from the light source and includes a plurality of uniformizing lenses arranged on an optical path; a condensing unit which condenses light from the uniformizing unit to emit the light to the display element and includes a plurality of condensing lenses sequentially arranged on the optical path, and the uniformizing unit and the condensing unit are arranged based on a width of one of a plurality of cell lenses forming the uniformizing lens and a width of an image displayed in the display element.

Abstract: Provided are an adapter assembly and method for compensating optical fibers for a length difference. The adapter assembly includes a first adapter, a second adapter, and a member. The first adapter is configured to be connected to at least one optical communication unit. The second adapter is configured to be connected to at least another optical communication unit and be coupled to the first adapter. The member is configured to be interposed between the first and second adapters for providing an optical signal transmission path between the optical communication units. Owing to the member, a length difference between optical fibers can be compensated for.

Abstract: Provided is an optical OFDM receiver. The optical OFDM receiver receives an optical signal dependent on the nonlinearity of a transmitter. The optical OFDM receives includes an optical down converter, a nonlinearity compensator, and an OFDM demodulator. The optical down converter converts the optical signal into an electrical signal. The nonlinearity compensator filters the electrical signal, for compensating distortion which is added to the optical signal when the transmitter performs optical modulation. The OFDM demodulator demodulates the distortion-compensated electrical signal in an OFDM scheme.

Abstract: Provided is a polarization division multiplexed optical OFDM transmitter. The polarization division multiplexed optical OFDM transmitter includes a data demultiplexer, a training symbol generation unit and an optical up-converter and polarization division multiplexing unit. The data demultiplexer divides a transmission signal into a plurality of groups. The training symbol generation unit allocates a plurality of training symbols for each OFDM data which is included in the respective multiplexed groups, and allocates repetitive data in a time domain for the respective training symbols for data of 0 to periodically appear for the respective training symbols in a frequency domain. The optical up-converter and polarization division multiplexing unit performs optical frequency band conversion and polarization division multiplexing on an output of the training symbol generation unit to output a polarization division multiplexed optical OFDM signal corresponding to a plurality of polarization components.

Abstract: Provided is an optical receiver used for an optical communication system, more particularly, a polarization split-phase shift demodulation coherent optical receiver. An optical hybrid includes a first optical splitter, a phase shift waveguide, a second optical splitter, and an optical coupler. The first optical splitter splits a first input optical signal to output first output optical signals. The phase shift waveguide receives the first output optical signals and controls and outputs the first output optical signals such that the first output optical signals have different phases. The second optical splitter splits a second input optical signal to output a plurality of second output optical signals. The optical coupler couples the first output optical signals one-to-one with the second output optical signals, respectively.

Abstract: Provided is an optical device. The optical device includes a multiplexer/demultiplexer, a multimode interference (MMI) coupler, a first waveguide, and second waveguides. The multiplexer/demultiplexer splits optical signals having a plurality of channels and received through a first port according to their wavelength to provide the split optical signals to second ports, or providing input optical signals having wavelengths difference from each other and received through the second ports to the first port. The multimode interference (MMI) coupler is connected to the first port. The first waveguide is connected to the MMI coupler. The second waveguides are connected to the second ports. The MMI coupler has a width decreasing toward the multiplexer/demultiplexer.

Abstract: An illumination unit and an image projection apparatus employing the same. The illumination unit includes: a first reflective surface reflecting light incident thereon; a light-emitting device generating and emitting illuminating light; and a second reflective surface reflecting light emitted from the light-emitting device to a light source surface that includes the light-emitting device.

Abstract: Provided is a frequency-tunable terahertz light source device. The frequency-tunable terahertz light source device satisfies a Littrow diffraction condition at a wavelength and simultaneously satisfies a Littman-Metcalf diffraction condition at another wavelength using a double diffraction grating having two grating periods. Thus, oscillations simultaneously occur at the two different wavelengths, such that a terahertz wave can be stably generated by beating of the two oscillation wavelengths. In addition, the frequency-tunable terahertz light source device can readily change a frequency up to several terahertz and can be fabricated in a small size.

Abstract: Provided is an upstream source light generator of a passive optical network (PON) system. The upstream source light generator includes an amplification part configured to amplify injection light, and a reflection part configured to receive the amplified injection light and generate reflection light by reflecting the amplified injection light with different optical delays according to wavelengths of the amplified injection light.

Abstract: An optical interleaver of a wavelength division multiplexing (WDM) system includes an optical coupler, first and second waveguides, a high reflection mirror, and first and second phase shifters. The coupler divides an input optical signal. The first waveguide branches off from the coupler in a first direction. The second waveguide branches off from the coupler in a second direction for providing an optical path different from that provided by the first waveguide. The high reflection mirror is disposed at an end of the first waveguide for reflecting a first optical signal incident onto the first waveguide. The first phase shifter is disposed at an end of the second waveguide for multiple-reflecting a second optical signal incident onto the second waveguide. The second phase shifter is disposed at the first or second waveguide for adjusting an optical path difference between the first and second waveguides by varying its refractive index.

Abstract: Provided is an integrated semiconductor light source using locking characteristic by an external light injection, including: an active region controlling an optical gain and an optical output by current injection; and a passive region having a structure integrated with the active region and moving a cavity mode by current injection or voltage application to lock injection light.

Abstract: A wavelength tunable laser diode using a double coupled ring resonator is provided. A new double coupled ring resonator structure is formed by a connection of two ring resonators having different radii so that stable laser oscillation occurs only in a resonant wavelength at which the two ring resonators are simultaneously resonated, and the effective refractive index of the two ring resonators is properly controlled differently for tunable laser oscillation wavelengths. The reproducibility of the optical coupling characteristics of the passive waveguides and the ring resonator can be assured by multi-mode couplers. This results in improved manufacturing productivity of the wavelength tunable laser diode. It is possible to amplify and output an output light without having an effect on oscillation wavelength characteristic by means of an optical amplifier integrated in an output end.

Abstract: Provided is a wavelength selective switch (WSS), and more particularly, a wavelength selective switch for electrically switching a wavelength without physical displacement. The wavelength selective switch includes an optical demultiplexer for dividing an input optical signal into signals having wavelengths corresponding to respective channels, selecting either the optical signal of each channel obtained by dividing the input optical signal or an optical signal input via an add port, and outputting the selected optical signal; and an optical multiplexer including an optical deflecting unit for individually deflecting the optical signals of the respective channels received from the optical demultiplexer according to supplied current or applied voltage, wherein the optical signal of each channel deflected by the optical deflecting unit is output to a specific output port.

Abstract: Provided is a frequency-tunable terahertz light source device. The frequency-tunable terahertz light source device satisfies a Littrow diffraction condition at a wavelength and simultaneously satisfies a Littman-Metcalf diffraction condition at another wavelength using a double diffraction grating having two grating periods. Thus, oscillations simultaneously occur at the two different wavelengths, such that a terahertz wave can be stably generated by beating of the two oscillation wavelengths. In addition, the frequency-tunable terahertz light source device can readily change a frequency up to several terahertz and can be fabricated in a small size.

Abstract: An illumination unit includes first, second, third, and fourth light source units to emit first, second, third, and fourth light beams of different wavelength bands, and a hexahedral color synthesis prism to synthesize the first, second, third, and fourth light beams emitted from the first, second, third, and fourth light source units to propagate the first, second, third, and fourth light beams can propagate along the same path with respect to each other.

Abstract: Provided is an optical deflector for deflecting radiation beams. The optical deflector includes: a peripheral region having a first effective refractive index; and a deflection pattern region having a predetermined shape and a second effective refractive index, wherein the second effective refractive index differs from the first effective refractive index. Here, due to the deflection pattern region having the predetermined shape, the radiation beams are deflected in a direction starting from a certain point. By using the optical deflector, the locus of a light source can be designed in one of various forms, such as a straight line, a circle, an ellipse, or a parabola.

Abstract: Provided is a tunable external cavity laser diode using a variable optical deflector wherein the variable optical deflector, in which a refractive index varies according to an electrical signal, is arranged in a triangular shape between a concave diffraction grating and a reflective mirror. Since a resonant frequency is changed using the electrical signal rather than the mechanical movement, the stable operation and continuous high-speed tenability may be enabled. In addition, when the tunable external cavity laser diode according to the present invention is implemented in an InP/InGaAsP/InP slab waveguide, a variable time determined by the carrier lifetime may be reduced to several nanoseconds or less, the miniaturization is enabled, and the manufacturing costs are significantly reduced due to the process simplification.

Abstract: An illumination system and a projection system capable of enhancing light efficiency and contrast. The projection system includes a display panel from which light incident to a projection lens unit is controlled according to the rotation of a plurality of micromirrors and an asymmetric stop which adjusts an angle of effective light incident from the display panel. The illumination system emitting light to the projection system includes: one or more light source units each including a single or an array of light emitting devices and having a light exit surface with an aspect ratio different from an aspect ratio of the display panel; and an aspect ratio adjusting unit adjusting the aspect ratio of the light such that the aspect ratio of the light exit surface of each of the light source units can be equal to the aspect ratio of the display panel.

Abstract: Provided are a tunable demultiplexer and a tunable laser, having an optical deflector in which a refractive index of a core layer of a deflection pattern region having a predetermined shape varies in response to an external electrical signal so that the optical deflector deflects incident light in the radial direction.