An optical modulator includes an optical modulation element including an optical waveguide formed on a substrate and a housing that accommodates the optical modulation element, the housing has a bottom surface wall having a quadrilateral shape in a plan view, first and second long side walls that are connected to two opposite edges of the bottom surface wall, and first and second short side walls that are shorter than the first and second long side walls and are connected to two other opposite edges of the bottom surface wall. An average wall thickness of the second long side wall is equal to or larger than an average wall thickness of the first long side wall. At least one of the first and second short side walls has an average thickness that is thinner than the average thickness of the first long side wall.

A bismuth and magnesium co-doped lithium niobate crystal includes Li.sub.2CO.sub.3, Nb.sub.2O.sub.5, Bi.sub.2O.sub.3 and MgO, wherein the molar ratio of [Li] and [Nb] is 0.90-1.00, the molar percentage of Bi.sub.2O.sub.3 in the mixture is 0.25-0.80%, and the molar percentage of MgO in the mixture is 3.0-7.0%. The bismuth and magnesium co-doped lithium niobate crystal has enhanced photorefraction, improved photorefractive sensitivity, shortened holographic grating saturation writing time, and the photorefractive diffraction efficiency can reach up to 17%. The response time is only 170 ms, when the holographic storage experiment is carried out using 488 nm continuous laser. Therefore, this crystal can be used in the field of holographic imaging.

An initial change and a secular change in an optical characteristic and a high frequency characteristic in a case where an optical modulator is mounted in a package of an optical transmission apparatus are suppressed while improving a space utilization rate in the package of the optical transmission apparatus. An optical modulator that is electrically connected to an electric circuit configured on a circuit board, includes: a package that houses an optical modulation element; and a signal input part or the like for inputting an electric signal for causing the optical modulation element to perform an modulation operation from the electric circuit, in which the package has, on a part of a bottom surface facing the circuit board, a first protrusion portion protruding from the bottom surface, and the signal input part is provided on an upper surface of the first protrusion portion.

In an optical modulator, high frequency characteristics are improved and the stability thereof is improved. An optical modulator includes: an optical element substrate that includes an optical waveguide and a plurality of electrodes that control light waves propagating through the optical waveguide; and a package case that houses the optical element substrate, in which a plurality of signal input terminals, respectively electrically connected to the plurality of electrodes, are provided on the bottom surface of the package case, and the plurality of signal input terminals respectively electrically connected to the plurality of electrodes provided on the optical element substrate are divided and disposed on the sides facing each other with the optical element substrate interposed therebetween.

An optical modulator that can effectively dissipate heat generated from the inside includes: an optical modulation element which includes an optical waveguide and a radio frequency electrode for controlling light waves propagating through the optical waveguide; a termination resistor electrically connected to the radio frequency electrode; a termination resistor board on which the termination resistor is disposed; and a package case, which houses the optical modulation element and the termination resistor board, in which a plurality of protrusion portions are formed on one external surface of the package case, and at least one of the protrusion portions is formed at a position on the external surface of the package case, which faces a position inside the package case where the termination resistor board is disposed with the package case in between.

A continuously tunable radio frequency (RF) sensor system is provided. The system includes a pump laser system that includes first and second pump lasers, at least one frequency modulator to modulate frequencies of first and second laser light from the pump lasers to first and second select frequencies, a switch system to selectively pass one of the first and second laser light, an amplifier to amplify the passed laser light, a frequency doubler to double the frequency of the amplified laser light to generate pump light. A laser source lock system is in communication with the pump laser system to ensure a frequency of the pump light is referenced to atoms in a vapor cell and provide a probe light. The pump light and probe light are transmitted through the vapor cell. A detector measures the probe light that passed through the vapor cell.

An optical waveguide structure comprises a nonlinear optical waveguide, straight segments in the nonlinear optical waveguide, and curved segments in the nonlinear optical waveguide. The nonlinear optical waveguide comprises a nonlinear optical material having a second order nonlinear coefficient for a nonlinear optical process in which the second order nonlinear coefficient changes with a direction of light propagation. The straight segments in the nonlinear optical waveguide are oriented such a nonlinear optical interaction with light generation that occurs with an overall constructive manner within the nonlinear optical waveguide in response to a light traveling though the nonlinear optical waveguide. The curved segments have a 90 degree bend, wherein the curved segments connect the straight segments to each other within in the nonlinear optical waveguide.

Provided is an optical modulating device including an incidence optical system, an optical modulating assembly including a plurality of nano-antennas that form a meta-grating based on a driving signal, the optical modulating assembly being configured to change a traveling direction of incidence light incident at an incidence angle from the incidence optical system based on an effective displacement of the meta-grating according to the driving signal, and an emission optical system configured to emit light steered by the optical modulating assembly, wherein the emission optical system is further configured to emit first-order diffraction light of the incidence light based on the meta-grating.

An optical modulator in which an optical signal is input from one side of a package, includes in the package, a chip that optically modulates the optical signal and in which an input waveguide and an output waveguide of the optical signal are led to mutually different destinations each being one end of the chip facing the one side of the package and a side surface of the chip orthogonal to the one end of the chip; an input optical system coupled to the input waveguide of the chip; and an output optical system coupled to the output waveguide of the chip.

An interface for an optical modulator and the optical modulator are described. The interface includes first and second differential line pairs. The first differential line pair has a first negative line and a first positive line arranged on opposing sides of a first waveguide. The first negative line is on a distal side of the first waveguide relative to a second waveguide. The first positive line is on a proximal side of the first waveguide relative to the second waveguide. The second differential line pair has a second negative line and a second positive line arranged on opposing sides of the second waveguide. The second negative line is on a distal side of the second waveguide relative to the first waveguide. The second positive line is on a proximal side of the second waveguide relative to the first waveguide. The first and second waveguides each include lithium niobate and/or lithium tantalate.