Abstract: An underwater optical communication device communicates with another underwater optical communication device. The underwater optical communication device is provided with an optical transmitter, an optical receiver, and a controller. The optical transmitter transmits laser light to another underwater optical communication device. The optical receiver receives laser light from another underwater optical communication device. The controller controls the optical transmitter and the optical receiver. The optical receiver is provided with a polarizing plate configured to transmit S-polarized light of natural light and suppress transmission of P-polarized light of natural light and a photodetector configured to detect laser light emitted from the polarizing plate.

Abstract: A light receiving device of optical communication equipment includes a condenser lens configured to condense incident light, a collimation lens having a focal length shorter than a focal length of the condenser lens, the collimation lens being configured to convert light from the condenser lens to parallel light, a bandpass filter having a filter surface on which the parallel light from the collimation lens is perpendicularly incident, the bandpass filter being configured to transmit only a wavelength of the incident light, and a light receiving element configured to detect light transmitted through the bandpass filter.

Abstract: An optical fiber laser module is provided with an optical fiber (2) for diffusing light, and a laser module housing (1) connected to the optical fiber. The laser module housing is provided with a laser light source (11) that outputs laser light to the optical fiber, and a light detector (14) that detects laser light that has been wave-guided through the full length of the optical fiber. The optical fiber is provided with: a light incident part (3a) provided inside the laser module housing, laser light from the laser light source being incident on the light incident part; and a terminal part (3) on which is formed a reflective film (4) that reflects the laser light that was incident on the light incident part and was wave-guided through the full length of the optical fiber so as to return the laser light to the light incident part.

Abstract: An optical fiber laser module is provided with an optical fiber (2) for diffusing light, and a laser module housing (1) connected to the optical fiber. The laser module housing is provided with a laser light source (11) that outputs laser light to the optical fiber, and a light detector (14) that detects laser light that has been wave-guided through the full length of the optical fiber. The optical fiber is provided with: a light incident part (3a) provided inside the laser module housing, laser light from the laser light source being incident on the light incident part; and a terminal part (3) on which is formed a reflective film (4) that reflects the laser light that was incident on the light incident part and was wave-guided through the full length of the optical fiber so as to return the laser light to the light incident part.

Abstract: The optical connector includes an insert-opening 3b into which the optical fiber 4 is inserted, a connection-opening 3a that positions the tip of the optical fiber inserted into an insert-opening to a desired laser light connection position, and a guide 2a that guides the optical fiber inserted into the insert-opening 3f, where the insert-opening is in-place on the non-optical-axis of the laser light to be connected and a position-difference between the connection-opening and the insert-opening is larger than the predetermined value.

Abstract: A periodic polarization reversal electrode, periodic polarization reversal structure forming method and periodic polarization reversal element. The element includes a plurality of stripe electrode sections with a stripe shape extending in parallel at a gap from each other, arranged in contact with the +Z surface of a ferroelectric crystal substrate; an insulation film arranged over the +Z surface so as to cover the plurality of stripe electrode sections; and an equipotential electrode section which has a portion that opposes at least a part of each of the plurality of stripe electrode sections across the insulation film and is arranged over the insulation film without contacting the ferroelectric crystal substrate or the plurality of stripe electrode sections, wherein an electric field is generated in the area of the ferroelectric crystal substrate directly below the plurality of stripe electrode sections by applying a voltage to the equipotential electrode section.

Abstract: A periodic polarization reversal electrode, periodic polarization reversal structure forming method and periodic polarization reversal element. The element includes a plurality of stripe electrode sections with a stripe shape extending in parallel at a gap from each other, arranged in contact with the +Z surface of a ferroelectric crystal substrate; an insulation film arranged over the +Z surface so as to cover the plurality of stripe electrode sections; and an equipotential electrode section which has a portion that opposes at least a part of each of the plurality of stripe electrode sections across the insulation film and is arranged over the insulation film without contacting the ferroelectric crystal substrate or the plurality of stripe electrode sections, wherein an electric field is generated in the area of the ferroelectric crystal substrate directly below the plurality of stripe electrode sections by applying a voltage to the equipotential electrode section.

Abstract: A semiconductor laser excited solid state laser device and method. The device including a semiconductor laser; a driving device; a solid state laser module which has maximum output efficiency at the set temperature and which generates, from excitation light, an output light of a predetermined output level when the optical noise is at or below a fixed level and the output level of the excitation light is the set output level; a single temperature adjustment device which adjusts the temperature of the semiconductor laser and the temperature of the solid state laser module; and a control device which controls the driving device such that the output light will be at the predetermined output level and controls the temperature adjustment device such that the temperature of the semiconductor laser and the solid state laser module will be the set temperature.

Abstract: The outer shape of a surface to be bonded of a first optical crystal member is formed as a shape in which the length in a direction parallel to an optical axis of the first optical crystal member differs from the length in a direction perpendicular to the optical axis of the first optical crystal member. The outer shape of a surface to be bonded of a second optical crystal member is formed as a shape coinciding with the outer shape of the surface to be bonded of the first optical crystal member or a shape obtained by enlarging or reducing the coinciding shape in an orientation in which an optical axis of the second optical crystal member and the optical axis of the first optical crystal member are adjusted to a prescribed angle.

Abstract: A semiconductor laser excited solid state laser device and method. The device including a semiconductor laser; a driving device; a solid state laser module which has maximum output efficiency at the set temperature and which generates, from excitation light, an output light of a predetermined output level when the optical noise is at or below a fixed level and the output level of the excitation light is the set output level; a single temperature adjustment device which adjusts the temperature of the semiconductor laser and the temperature of the solid state laser module; and a control device which controls the driving device such that the output light will be at the predetermined output level and controls the temperature adjustment device such that the temperature of the semiconductor laser and the solid state laser module will be the set temperature.

Abstract: The outer shape of a surface to be bonded of a first optical crystal member is formed as a shape in which the length in a direction parallel to an optical axis of the first optical crystal member differs from the length in a direction perpendicular to the optical axis of the first optical crystal member. The outer shape of a surface to be bonded of a second optical crystal member is formed as a shape coinciding with the outer shape of the surface to be bonded of the first optical crystal member or a shape obtained by enlarging or reducing the coinciding shape in an orientation in which an optical axis of the second optical crystal member and the optical axis of the first optical crystal member are adjusted to a prescribed angle.

Abstract: A current is observed while applying a gradually increasing voltage between electrodes formed front and rear surfaces of a substrate, and then poled regions are formed by applying a DC voltage, which has a voltage value at that time or another voltage value obtained by adding a predetermined value to the voltage value (i.e., an inverted voltage value or a voltage value obtained by adding a predetermined voltage to the inverted voltage value), for a predetermined time when an inverted current is observed.

Abstract: A polarization inverting region is formed by using a board comprising a single crystal of lithium tatalate of a stoichiometric composition or near to the stoichiometric composition and applying a direct current electric field having an electric field intensity equal to or lower than 5 [kV/mm] for 1 [second] or longer. A periodically poled region can be formed without needing a complicated constitution for applying a pulse voltage or a complicated constitution for applying a strong electric field.

Abstract: A current is observed while applying a gradually increasing voltage between electrodes formed front and rear surfaces of a substrate, and then poled regions are formed by applying a DC voltage, which has a voltage value at that time or another voltage value obtained by adding a predetermined value to the voltage value (i.e., an inverted voltage value or a voltage value obtained by adding a predetermined voltage to the inverted voltage value), for a predetermined time when an inverted current is observed.

Abstract: A polarization inverting region is formed by using a board comprising a single crystal of lithium tatalate of a stoichiometric composition or near to the stoichiometric composition and applying a direct current electric field having an electric field intensity equal to or lower than 5 [kV/mm] for 1 [second] or longer. A periodically poled region can be formed without needing a complicated constitution for applying a pulse voltage or a complicated constitution for applying a strong electric field.