The present invention provides a configuration of a novel optical transmitter which outputs stable PDM signals. The novel optical transmitter generates phase conjugate light using a single second-order non-linear optical element included in a phase conjugate light generator with a looped configuration. A relative phase of main signal light with respect to excitation light and phase conjugate light of the main signal light stabilizes between two polarized components, and a PDM signal including a pair of a polarization-multiplexed signal and phase conjugate light in a stable phase state can be generated and transmitted. The present invention can provide an optical transmitter that generates a PDM signal in which a variation in a phase between quadrature polarized waves is suppressed. By stabilizing quality of a PDM transmission signal on a side of the optical transmitter, a phase sensitive amplifier in a polarization diversity configuration can be operated in a stable manner.

A highly-efficient ridge waveguide includes a base substrate of a single-crystal and a core substrate made of a nonlinear optical medium, the base substrate and the core substrate being directly bonded, and includes a thin film layer formed on a surface of the core substrate on the upper side of a periodically polarization-reversed structure, and becomes a wavelength conversion element. A direct bonding method through thermal diffusion is applied to bonding. The core substrate has a ridge structure formed in a light propagating direction and a reversed structure formed by processing this. A surface of the core substrate is ground and a thin film layer is formed on the ground surface. A core formed by digging a core layer of the core substrate in an unbonded state is provided on an upper surface of an undercladding layer of the base substrate in a bonded state. Two side surfaces of the core are in contact with an air layer.

The invention relates to a method for producing waveguides (201) from a material (202) of the KTP family comprising the following method steps: b) treating the material (202) in such a way that a periodic poling of the material (202) is achieved, c), treating the material (202) in a molten salt bath (309c), which contains rubidium ions, characterized in that the molten salt bath (309c) which contains rubidium ions in step c) satisfies the following boundary conditions: the mole fraction of rubidium nitrate (RbNO.sub.3) in the melt lies in the range of 86-90 mol % at the beginning of the treatment, the mole fraction of potassium nitrate (KNO.sub.3) in the melt lies in the range of 10-12 mol % at the beginning of the treatment, the mole fraction of barium nitrate (Ba(NO.sub.3).sub.2) in the melt lies in the range of 0.5-1 mol % at the beginning of the treatment, the temperature of the melt lies in the range of 357363 C. during the treatment.

Thus the problem is solved, when reversing the known method steps, of achieving substantially identical diffusion depths of the ions during the ion exchange in order to produce periodically poled waveguides as free of corrugation as possible.

A wavelength conversion optical device includes: a substrate having a virtual plane and first and second regions and including multiple first crystal regions and multiple second crystal regions. Each of the multiple first crystal regions includes a pair of portions arranged in a direction intersecting a first plane with the first plane interposed therebetween, the first plane being located in the first region, and directions of spontaneous polarizations of each of the pair of portions being directions away from the first plane. Each of the multiple second crystal regions includes a pair of portions arranged in a direction intersecting a second plane with the second plane interposed therebetween, the second plane being located in the second region. Directions of spontaneous polarizations of each of the pair of portions being directions away from the second plane.

A wavelength conversion optical device includes: a substrate having a virtual plane and first and second regions and including multiple first crystal regions and multiple second crystal regions. Each of the multiple first crystal regions includes a pair of portions arranged in a direction intersecting a first plane with the first plane interposed therebetween, the first plane being located in the first region, and directions of spontaneous polarizations of each of the pair of portions being directions away from the first plane. Each of the multiple second crystal regions includes a pair of portions arranged in a direction intersecting a second plane with the second plane interposed therebetween, the second plane being located in the second region. Directions of spontaneous polarizations of each of the pair of portions being directions away from the second plane.

A resonant-structured optical transistor includes a nonlinear medium which generates a second harmonic wave through second-order nonlinear interaction with an incident pump wave, and generates an amplified signal wave and a converted wave having a difference frequency through second-order nonlinear interaction between the incident signal wave and the second harmonic wave, a first mirror which transmits, to the nonlinear medium, the pump wave or the signal wave, and reflects the second harmonic wave on one surface of the nonlinear medium, and a second mirror which transmits the pump wave, the signal wave, or the converted wave, and reflects the second harmonic wave on another surface of the nonlinear medium. The pump wave is incident to the nonlinear medium through the first mirror in a first operation mode, and the pump wave and the signal wave are incident to the nonlinear medium through the first mirror in a second operation mode.

A resonant-structured optical transistor includes a nonlinear medium which generates a second harmonic wave through second-order nonlinear interaction with an incident pump wave, and generates an amplified signal wave and a converted wave having a difference frequency through second-order nonlinear interaction between the incident signal wave and the second harmonic wave, a first mirror which transmits, to the nonlinear medium, the pump wave or the signal wave, and reflects the second harmonic wave on one surface of the nonlinear medium, and a second mirror which transmits the pump wave, the signal wave, or the converted wave, and reflects the second harmonic wave on another surface of the nonlinear medium. The pump wave is incident to the nonlinear medium through the first mirror in a first operation mode, and the pump wave and the signal wave are incident to the nonlinear medium through the first mirror in a second operation mode.

A monolithically integrated wavelength converted photonic integrated circuit (PIC) is fabricated by forming a trench in the PIC's insulating layer to expose a portion of an output waveguide that transmits a photonically processed optical signal at frequency 1. A non-linear waveguide formed of a non-linear material with non-linear susceptibility at frequency 1 and a transmission bandwidth spanning both 1 and m*1 where m is an integer of at least two is fabricated in direct physical contact with the exposed portion of the output waveguide. A patterned structure is fabricated in or on the non-linear waveguide to enhance non-linear susceptibility to generate an optical signal at frequency m*1, which may be emitted directly or coupled to an optical antenna.

A monolithically integrated wavelength converted photonic integrated circuit (PIC) is fabricated by forming a trench in the PIC's insulating layer to expose a portion of an output waveguide that transmits a photonically processed optical signal at frequency 1. A non-linear waveguide formed of a non-linear material with non-linear susceptibility at frequency 1 and a transmission bandwidth spanning both 1 and m*1 where m is an integer of at least two is fabricated in direct physical contact with the exposed portion of the output waveguide. A patterned structure is fabricated in or on the non-linear waveguide to enhance non-linear susceptibility to generate an optical signal at frequency m*1, which may be emitted directly or coupled to an optical antenna.

An apparatus includes a substrate transmissive of electromagnetic energy of at least a plurality of wavelengths, having a first end, a second end, a first major face, a second major face, at least one edge, a length, a width, and a thickness, at least a first output optic that outputs electromagnetic energy the substrate; and a first input optic oriented and positioned to provide electromagnetic energy into the substrate via at least one of the first or the second major face of the substrate. The first output optic is laterally spaced from the first input optic. A number of reflectors and optional absorbers may be positioned proximate the first major face and/or the second major face to structure electromagnetic energy and/or to translate such from the first input optic to the first output optic. The apparatus may be part of a spectrometer or other optical system.