Abstract: This optical coupler for coupling a plurality of visible light beams having different wavelengths includes: a substrate made of a material different from lithium niobate; and an optical coupling function layer formed on a main surface of the substrate. The optical coupling function layer includes: two multimode-interference-type optical coupling parts; optical-input-side waveguides and an optical-output-side waveguide connected to one multimode-interference-type optical coupling part, and optical-input-side waveguides and an optical-output-side waveguide connected to the other multimode-interference-type optical coupling part. The multimode-interference-type optical coupling parts, the optical-input-side waveguides, and the optical-output-side waveguides are made of a lithium niobate film.

Abstract: This optical modulator includes an optical modulation element having a first optical waveguide, a second optical waveguide, a first electrode configured to apply an electric field to the first optical waveguide, and a second electrode configured to apply an electric field to the second optical waveguide; and a control unit configured to control an applied voltage between the first electrode and the second electrode. The control unit sets Vpp to 0.06×V??Vpp?0.4×V? when a half-wavelength voltage of the optical modulation element is V? and an applied voltage width that is an amplitude of an applied voltage applied to the optical modulation element is Vpp, and sets Vn?Vmin?Vn+0.29×V? or Vn?0.29×V??Vmax?Vn when a minimum value and a maximum value of a voltage applied to the optical modulation element are respectively Vmin and Vmax and a null point voltage of the optical modulation element is Vn.

Abstract: The optical modulator includes an optical modulation element having a first optical waveguide, a second optical waveguide, a first electrode which applies an electric field to the first optical waveguide, and a second electrode which applies an electric field to the second optical waveguide, and a control unit configured to control an applied voltage between the first electrode and the second electrode. When a half-wave voltage of the optical modulation element is V? and a null point voltage of the optical modulation element is Vn, the control unit sets an operating point Vd in a range of Vn+0.50V??Vd?Vn+0.75V? or Vn?0.75V??Vd?Vn?0.50V? and sets an applied voltage width Vpp, which is an amplitude of an applied voltage applied to the optical modulation element, in a range of 0.22V??Vpp?0.50V?.

Abstract: This optical modulation element includes a first optical waveguide, a second optical waveguide, a first electrode for applying an electric field to the first optical waveguide, and a second electrode for applying an electric field to the second optical waveguide. The first optical waveguide and the second optical waveguide each include a ridge-shaped portion protruding from a first surface of a lithium niobate film. A first interaction length L1 that is a length of a part of the first electrode overlapping the first optical waveguide in a longitudinal direction is 0.9 mm or more and 20 mm or less. A second interaction length L2 that is a length of a part of the second electrode overlapping the second optical waveguide in the longitudinal direction is 0.9 mm or more and 20 mm or less.

Abstract: A optical modulation element includes a substrate made of a material different from lithium niobate, a lithium niobate film formed on a main surface of the substrate, the lithium niobate film including a Mach-Zehnder-type optical waveguide having a first ridge and a second ridge that function as a first optical waveguide and a second optical waveguide, respectively, wherein both the first ridge and the second ridge having a cross-sectional shape fixed portion, at least one of the first ridge and the second ridge having a cross-sectional shape non-fixed portion in which the cross-sectional shape is different from that of the cross-sectional shape fixed portion, and the optical output obtained when the DC bias voltage applied between the first electrode and the second electrode is 0 (V) is smaller than the maximum of the optical output obtained when the DC bias voltage is changed in a predetermined voltage range.

Abstract: A method and apparatus for controlling a video camera recorder or the like, capable of flexibly meeting user demands for image quality, recording time, etc. When recording information on a rewritable optical recording medium, the recording mode for the optical recording medium is selected at least from between write-once and rewritable based on a set recording rate. Before recording, the recording status of the optical recording medium is also determined at least between an unrecorded area and a recorded area.

Abstract: An optical head device (optical head) for a multi-layered optical recording medium has a focus control mechanism that makes use of astigmatism. The focus control mechanism has a sensor lens that includes a cylindrical lens. The focus control mechanism causes a light beam having passed through the sensor lens to have astigmatism, thereby being focused linearly in the Y direction on a front focal line located closer to the sensor lens and focused linearly in the X direction at a rear focal line located farther therefrom. The optical head also includes a photodetector which is disposed between the front focal line and the rear focal line to detect a focal position from the shape of a light beam. At the position of the front focal line, a shield plate with a window portion is disposed. The window portion has a size so as to allow the focal line to pass therethrough and shield stray light reflected from an unfocused recording layer.

Abstract: A next-generation optical recording medium has two or more information layers which include a translucent information layer. The translucent information layer has a recording film and an interface layer, provided adjacent to the recording film on the side of the light incident surface. The recording film is made of a phase change material having SbxTeyGez elements and elemental ratios. Y satisfies 5?y?15 and z satisfies 5?z?15. When In having an elemental ratio of a is further added and x+y+z+a=100 holds, a satisfies 4?a?15. The interface layer comprises of ZrO2—Cr2O3 film thickness of which is in a range of from 2 nm to 10 nm. When ZrO2:Cr2O3?C:D (mol %), the compositional ratios ZrO2 and Cr2O3 in the ZrO2—Cr2O3 film, holds, the C satisfies 20?C?90, and the D satisfies 10?D?80, and the C and the D satisfy C+D=100. The ZrO2 is stabilized ZrO2 which contains Y2O3, when ZrO2:Y2O3=(100?X):X (mol %), the compositional ratios ZrO2 and Y2O3 in the stabilized ZrO2, holds, the X satisfies 2?X?10.

Abstract: An information readout method for an optical information medium comprising an information recording layer having pits or recorded marks representative of information data involves the step of irradiating a laser beam to the information recording layer through an objective lens for providing readings of the pits or recorded marks. When the laser beam has a wavelength ? of 400 to 410 nm, the objective lens has a numerical aperture NA of 0.70 to 0.85, and the pits or recorded marks have a minimum size PL of up to 0.36?/NA, readout is carried out at a power Pr of at least 0.4 mW for the laser beam. When the laser beam has a wavelength ? of 630 to 670 nm, the objective lens has a numerical aperture NA of 0.60 to 0.65, and the pits or recorded marks have a minimum size PL of up to 0.36?/NA, readout is carried out at a power Pr of at least 1.0 mW for the laser beam. Pits or recorded marks of a size approximate to the resolution limit determined by diffraction can be read out at a high C/N.

Abstract: It is an object of the present invention to provide a method of recording information to an optical recording medium that is suited to achieving high data transfer rates. The method of recording information according to the present invention is adapted for recording information to an optical recording medium by forming on the optical recording medium a plurality of recording marks selected from a group consisting of several types of recording marks each with different lengths, wherein a bottom power of a laser beam used for forming at least one recording mark contained in the group is set to be higher than a reproducing power of a laser beam used for reproducing information. According to the present invention, since the bottom power helps to erase a recording mark, it is possible to maintain a high erase efficiency even when information is recorded by setting a high data transfer rate.

Abstract: An optical head device (optical head) for a multi-layered optical recording medium has a focus control mechanism that makes use of astigmatism. The focus control mechanism has a sensor lens that includes a cylindrical lens. The focus control mechanism causes a light beam having passed through the sensor lens to have astigmatism, thereby being focused linearly in the Y direction on a front focal line located closer to the sensor lens and focused linearly in the X direction at a rear focal line located farther therefrom. The optical head also includes a photodetector which is disposed between the front focal line and the rear focal line to detect a focal position from the shape of a light beam. At the position of the front focal line, a shield plate with a window portion is disposed. The window portion has a size so as to allow the focal line to pass therethrough and shield stray light reflected from an unfocused recording layer.

Abstract: In an optical information medium having an information bearing surface having projections and depressions and/or capable of forming recorded marks, a functional layer is added. The information borne on the information bearing surface can be read by using reading light of a wavelength longer than 4NA·PL wherein PL is the minimum size of the projections and depressions or the recorded marks and NA is the numerical aperture of a reading optical system, setting the power of the reading light within such a range that the functional layer does not change its complex index of refraction, and irradiating the reading light to the information bearing surface constructed by the functional layer or to the information bearing surface through the functional layer or to the functional layer through the information bearing surface. The medium enables reading at a high resolution beyond the diffraction limit.

Abstract: An optical recording medium has a recording layer formed of a plurality of reflection hologram layers. A spacer layer is interposed between the respective reflection hologram layers. The reflection hologram layer is made of a material having a thermal threshold value which allows, when being irradiated with a recording laser beam, local absorbed heat to vary hologram diffraction conditions at a focal position, and allows the hologram to be retained at non-focal positions. The spacer layer is made of a material which is insensitive to a laser beam of a recording wavelength and which has a smaller extinction coefficient than that of the reflection hologram layer.

Abstract: In a data recording and readingout system in which data is recorded and readout, or is readout on, or from an optical recording medium 1 by irradiating a laser beam having a wavelength “?” via an objective lens of a numerical aperture “NA” onto said optical recording medium, while the optical recording medium contains a layered structure formed by sandwiching a dielectric layer 6 between a recording layer 7 and an optical absorption layer 5, with respect to the optical recording medium 1 arranged in such a manner that data recorded by a recorded mark train can be readout and the recorded mark train contains a recorded mark smaller than, or equal to a limit of resolution, the laser beam is irradiated via the objective lens and a solid immersion lens having a refractive index “n” which is positioned between the optical recording medium and the objective lens, so that the data is recorded and readout, or is readout with respect to the optical recording medium by a recorded mark train which contains a recorded ma

Abstract: A multi-layered optical recording medium is provided of which the manufacturing costs is significantly reduced. The multi-layered optical recording medium has multiple information recording layers and at least two layers of the information recording layers have the same medium-side address information. This configuration allows for reducing the types of master stampers and thus reducing manufacturing costs.

Abstract: An information readout method for an optical information medium comprising an information recording layer having pits or recorded marks representative of information data involves the step of irradiating a laser beam to the information recording layer through an objective lens for providing readings of the pits or recorded marks. When the laser beam has a wavelength ? of 400 to 410 nm, the objective lens has a numerical aperture NA of 0.70 to 0.85, and the pits or recorded marks have a minimum size PL of up to 0.36?/NA, readout is carried out at a power Pr of at least 0.4 mW for the laser beam. When the laser beam has a wavelength ? of 630 to 670 nm, the objective lens has a numerical aperture NA of 0.60 to 0.65, and the pits or recorded marks have a minimum size PL of up to 0.36?/NA, readout is carried out at a power Pr of at least 1.0 mW for the laser beam. Pits or recorded marks of a size approximate to the resolution limit determined by diffraction can be read out at a high C/N.

Abstract: An information readout method for an optical information medium comprising an information recording layer having pits or recorded marks representative of information data involves the step of irradiating a laser beam to the information recording layer through an objective lens for providing readings of the pits or recorded marks. When the laser beam has a wavelength ? of 400 to 410 nm, the objective lens has a numerical aperture NA of 0.70 to 0.85, and the pits or recorded marks have a minimum size PL of up to 0.36?/NA, readout is carried out at a power Pr of at least 0.4 mW for the laser beam. When the laser beam has a wavelength ? of 630 to 670 nm, the objective lens has a numerical aperture NA of 0.60 to 0.65, and the pits or recorded marks have a minimum size PL of up to 0.36?/NA, readout is carried out at a power Pr of at least 1.0 mW for the laser beam. Pits or recorded marks of a size approximate to the resolution limit determined by diffraction can be read out at a high C/N.

Abstract: An optical recording medium includes a substrate, a first recording layer formed on the substrate and containing an element selected from the group consisting of Si, Ge, C, Sn, Zn and Cu as a primary component, and a second recording layer located in the vicinity of the first recording layer and containing Al as a primary component, the optical recording medium being constituted to be irradiated by a laser beam projected onto the side opposite from the substrate and the total thickness of the first recording layer and the second recording layer being equal to or thinner than 40 nm. According to the thus constituted optical recording medium, it is possible to decrease a noise level and improve a C/N ratio in a reproduced signal.

Abstract: A method and apparatus for controlling a video camera recorder or the like, capable of flexibly meeting user demands for image quality, recording time, etc. When recording information on a rewritable optical recording medium, the recording mode for the optical recording medium is selected at least from between write-once and rewritable based on a set recording rate. Before recording, the recording status of the optical recording medium is also determined at least between an unrecorded area and a recorded area.

Abstract: An optical recording medium is provided which includes two or more information layers in which an Sb-based eutectic material is used as the material for a recording film of a translucent information layer. There is also provided a recording film material for the optical recording medium. The translucent information layer is configured to include a recording film formed of a phase change material SbxGeyInz containing Sb, Ge, and In in an atomic ratio of x:y:z, where 5?y?15 and 4?z?15 are satisfied. The recording film further includes Te in an atomic ratio of a, provided that x+y+z+a=100 and 4?a?15 are satisfied. An interface layer formed of a ZrO2—Cr2O3 film having a thickness of 2 nm or more and 10 nm or less is provided on the laser beam incident side of the recording film. When the compositional ratio of the ZrO2—Cr2O3 film is given by ZrO2:Cr2O3=B:C (mol %), 20?B?90, 10?C?80, and B+C=100 are satisfied.