Wavelength conversion apparatus

A wavelength conversion apparatus, including,

• at least any one of a second-order nonlinear optical element configured to receive excitation light and signal light input from optical fibers on an input side and perform phase sensitive amplification on the signal light, a second-order nonlinear optical element configured to receive excitation light and signal light input from optical fibers on an input side and perform difference frequency generation from the signal light, or a second-order nonlinear optical element configured to receive excitation light and a plurality of signal light input front optical fibers on an input side and perform sum frequency generation from the plurality of signal light,
• wherein the wavelength conversion apparatus outputs, to an optical fiber on an output side, any one of the light having been subjected to the phase sensitive amplification that is output from the corresponding second-order nonlinear optical element, the light generated by the difference frequency generation that is output from the corresponding second-order nonlinear optical element, or the light generated by the stun frequency generation that is output from the corresponding second-order nonlinear optical element,
• the wavelength conversion apparatus comprising:
• reflection suppressors on surfaces of optical elements excluding the second-order nonlinear optical element in the wavelength conversion apparatus between the optical fibers on the input side and the optical fiber on the output side, and on an end surface of the optical fiber on the output side, where the reflection suppressors are configured to suppress reflection by unwanted light generated in at least any one of a wavelength band in accordance with the excitation light and the signal light, a wavelength band in accordance with the difference frequency generation, or a wavelength band in accordance with the sum frequency generation, excluding the light having been subjected to the phase sensitive amplification, the light generated by the difference frequency generation, or the light generated by the sum frequency generation to be output the optical fiber on the output side, and
• a selective transmission-reflection unit that is provided between the second-order nonlinear optical element and the optical fiber on the output side, and that is configured to prevent optical coupling to the optical fiber on the output side,
• wherein the selective transmission-reflection unit is formed of two 45-degree mirrors arranged in parallel to each other,
• of the two 45-degree mirrors, at a surface of a first 45-degree mirror disposed at a position optically close to the second-order nonlinear optical element, the signal light and the light generated by the difference frequency generation are reflected, and the excitation light, the light generated by the sum frequency generation, the light of the wavelength band of two thirds of the excitation light and the light of the wavelength band of two thirds of the light generated by the sum frequency generation are transmitted, and at a rear surface of the first 45-degree mirror, reflection by the signal light, the light generated by the difference frequency generation, the excitation light and the light generated by the sum frequency generation is prevented, and the light of the wavelength band of two thirds of the excitation light and the light of the wavelength band of two thirds of the light generated by the sum frequency generation are reflected, and
• of the two 45-degree mirrors, at a surface of a second 45-degree mirror disposed at a position optically far from the second-order nonlinear optical element, the signal light and the light generated by the difference frequency generation are reflected, and the excitation light, the light generated by the sum frequency generation, the light of the wavelength band of two thirds of the excitation light and the light of the wavelength band of two thirds of the light generated by the sum frequency generation are transmitted, and at a rear surface of the second 45-degree mirror, reflection by the light of all the wavelength bands is prevented,
• wherein the selective transmission-reflection unit performs any one of separating the excitation light and the signal light, and light having a wavelength of two thirds of the excitation light from one another, separating the light generated by the difference frequency generation and the excitation light, and light having a wavelength of two thirds of the excitation light from one another, or separating the signal light and light generated by the sum frequency generation, and light having a wavelength of two thirds of the light generated by the sum frequency generation from one another, and prevents the separated light having the wavelength of two thirds of the excitation light or the separated light having the wavelength of two thirds of the light generated by the sum frequency generation from being optically coupled to the optical fiber on the output side.