An aim is to provide an optical coupler that contributes increasing pump-efficiency in an optical amplifier, and the optical amplifier. The optical amplifier includes: a main optical fiber that includes a core transmitting signal light, an inner cladding portion formed around an outer periphery of the core and having a refractive index lower than a refractive index of the core, and an outer cladding portion formed around an outer periphery of the inner cladding portion and having a refractive index lower than the refractive index of the inner cladding portion, a part of the outer cladding portion of which in a longitudinal direction being removed; and at least one pump-light input-output optical fiber that is fusion-spliced to the inner cladding portion of the main optical fiber at the portion where the outer cladding portion is removed, an average refractive index of which in a contact region where the pump-light input-output optical fiber is in contact with the inner cladding portion being larger than the refractive index of the inner cladding portion. Pump-light propagating in the pump-light input-output optical fiber is coupled to the inner cladding portion from the contact region and propagates in the inner cladding portion, or the pump-light propagating in the inner cladding portion is coupled to the pump-light input-output optical fiber from the contact region and propagates in the pump-light input-output optical fiber.

A multi-wavelength single-frequency optical fiber laser source for a laser radar system includes a resonant cavity composed of a high-reflectivity chirped optical fiber grating, a high gain optical fiber and a low-reflectivity chirped optical fiber grating, a single-mode semiconductor pump laser served as a pump light source, an optical wavelength division multiplexer, an optical coupler, an optical isolator, an optical circulator, an optical filter module, and a semiconductor optical amplifier. The pump light source performs optical fiber core pumping with respect to the high gain optical fiber. A portion of the wide-spectrum laser is filtered by the optical filter module to obtain a wavelength corresponding to a specific central frequency. Multi-wavelength laser lasing with a narrow linewidth and single longitudinal mode is implemented by combining a short linear resonant cavity structure and the optical filter module.

A pump reflector for efficiently recycling unabsorbed pump radiation in a diode-pumped fiber laser includes a core for guiding a laser beam, a pump cladding, and a tapered capillary tube. Pump radiation is adiabatically guided in the tapered capillary tube, which includes a mirror that is reflective for the pump radiation. The pump reflector may be packaged as a fiber component for co-propagating or counter-propagating fiber laser amplifiers and resonators.

An optical parametric oscillator (OPO) system comprises an optical waveguide including a hollow core containing a fluid, wherein the optical waveguide is configured to receive pump light and to convert the pump light into signal light and idler light via a third order non-linear optical effect. The OPO system further comprises an optical feedback arrangement for recycling at least a portion of the signal light and/or for recycling at least a portion of the idler light in an optical cavity that includes the optical waveguide. The OPO system may be used, in particular though not exclusively, in metrology, gas and solid-state spectroscopy, laser-assisted manufacturing, semiconductor technology, biomedicine, healthcare, and scientific laboratory use.

A DUV laser includes an optical bandwidth filtering device, such as etalon, which is disposed outside of the laser oscillator cavity of the fundamental laser, and which directs one range of wavelengths into one portion of a frequency conversion chain and another range of wavelengths into another portion of the frequency conversion train, thereby reducing the bandwidth of the DUV laser output while maintaining high conversion efficiency in the frequency conversion chain.

Because a light amplification device using a multicore optical fiber provides low utilization efficiency of excitation light according to a cladding excitation system, the present disclosure provides a light amplification device including: a first optical waveguide including a first light amplification medium; a second optical waveguide including a second light amplification medium; a first excitation light introducing circuit for introducing first excitation light for exciting the first light amplification medium into the first optical waveguide; and a first residual excitation light introducing circuit for introducing first residual excitation light which is output from the first optical waveguide and has a wavelength component of the first excitation light, into the second optical waveguide.

A multi-wavelength single-frequency optical fiber laser source for a laser radar system includes a resonant cavity composed of a high-reflectivity chirped optical fiber grating, a high gain optical fiber and a low-reflectivity chirped optical fiber grating, a single-mode semiconductor pump laser served as a pump light source, an optical wavelength division multiplexer, an optical coupler, an optical isolator, an optical circulator, an optical filter module, and a semiconductor optical amplifier. The pump light source performs optical fiber core pumping with respect to the high gain optical fiber. A portion of the wide-spectrum laser is filtered by the optical filter module to obtain a wavelength corresponding to a specific central frequency. Multi-wavelength laser lasing with a narrow linewidth and single longitudinal mode is implemented by combining a short linear resonant cavity structure and the optical filter module.

In optical amplifiers that use a multicore optical fiber, the absorption efficiency of excitation light in an optical amplification medium is low and the amplification efficiency of light intensity becomes lower in the cladding excitation method; therefore, an optical amplification apparatus according to the present invention includes an optical amplification medium, having a gain in a wavelength band of signal light, configured to receive the signal light; excitation light introduction means for introducing, into the optical amplification medium, excitation light to excite the optical amplification medium; and residual excitation light introduction means for introducing, into the optical amplification medium, residual excitation light output from the optical amplification medium, the residual excitation light having a wavelength component of the excitation light.

The system and method of integrated seed and high power pump source generates two wavelengths outside the effective gain bandwidth of a single gain medium without using two unique pump sources in a fiber amplifier train. The system and method uses a single pump power oscillator that passes a seed wavelength with no loss and minimal amplification to pump integrated amplifiers in both directions (forward and backward) resulting in amplification of the seed wavelength.

Aspects of an optical communications network are described that include two or more optical fibers arranged to allow communication in the same or in opposite directions. The optical network includes a first optical amplifier coupled to the first optical fiber, a second optical amplifier coupled to the second optical fiber, and an optical coupler that allows excess optical power from the first optical fiber to be provided for amplification of signals traversing the second optical fiber. The disclosed systems and devices thus enable excess power from one channel to be utilized to enable amplification of signals traveling on a different channel.