A fiber laser amplifier system including a first dual-clad delivery fiber receiving a signal beam and a pump beam, a doped amplifying fiber coupled to the first delivery fiber and receiving the signal beam and the pump beam, and amplifying the signal beam using the pump beam, and a second dual-clad delivery fiber coupled to the amplifying fiber and receiving the amplified signal beam and the pump beam. The system also includes an endcap having an input facet and an output facet. The input facet is coupled to the second delivery fiber and receives the amplified signal beam and the pump beam, and the output facet is configured to pass the amplified signal beam and reflect the pump beam back onto the second delivery fiber to be directed back to the doped amplifying fiber.

A hybrid optical amplifier is proposed that includes a preamplifier element formed of single-clad Ho-doped optical fiber and a power amplifier element formed of single-clad Tm-doped (or Tm—Ho co-doped) optical fiber. The preamplifier is used to impart gain to an input signal propagating at a wavelength λ.sub.S in the presence of a first pump beam operating at λ.sub.P1, creating an amplified output over a defined transmission bandwidth. The power amplifier element is disposed at the output of the preamplifier element and provides an additional level of gain to the output of the preamplifier element in the presence of a second pump beam operating at λ.sub.P2. A passband filter may be used between the preamplifier and the power amplifier to ensure that only wavelength components within the defined transmission bandwidth are applied as an output to the power amplifier.

The present disclosure provides an optical amplifier using an optical fiber. The optical fiber includes a single-mode optical fiber in which a plurality of rare earth elements is doped simultaneously; first and second optical fiber gratings disposed at opposite sides of the optical fiber, respectively, and totally reflecting light having a wavelength in a specific range; a pumping light source configured to generate a pumping light to excite rare earth ions in the optical fiber; and an optical coupler connected to the optical fiber and configured to transmit a light signal generated from a light source and the pumping light generated from the pumping light source to the optical fiber. Therefore, it is possible to obtain efficient amplification of a light signal through a simple configuration using the rare earth elements-doped optical fiber.

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.

A laser system according to an embodiment of the present invention includes an oscillation unit to generate a laser output, a connection unit to connect the oscillation unit with an optical fiber loop, an amplifying unit to amplify the laser output on the optical fiber loop, a conversion unit disposed on the optical fiber loop to convert pulsed wave laser output into continuous wave laser output, and an output unit disposed between the connection unit and the conversion unit to split a part of the laser output toward the conversion unit. The system for generating a high output pulsed wave laser and converting the pulsed wave laser into a continuous wave laser may be implemented in a simple structure and small size with high stability and high reproducibility. In addition, a high output laser may be obtained. Also, since conversion from the pulsed wave into the continuous wave is easy, both of the high output pulsed wave and the high output continuous wave may be obtained as necessary.

A bi-directionally pumped PM fiber amplifier includes an amplifier input coupled to a first WDM coupler and a second WDM coupler providing an amplifier output. A doped fiber is between the WDM couplers. A first pump light source emitting at a first wavelength along a first polarization axis is coupled to the WDM coupler through a polarization beam combiner/splitter and a polarization rotator is for downstream pumping of the doped fiber with rotated light relative to the first polarization. The fiber is upstream pumped with light having the first polarization using a second pump light source emitting at the first wavelength/first polarization, by an output of an optical power splitter with its input coupled to the first pump light source, or by a fiber-coupled rotator mirror coupled to the second WDM coupler.

An optical amplification apparatus 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, wherein the residual excitation light introduction means includes, on a side of one end of the optical amplification medium, residual excitation light multiplexing means for multiplexing the signal light and the residual excitation light, and on a side of another end of the optical amplification medium, space propagation type wavelength demultiplexing means for wavelength-demultiplexing the signal light and the residual excitation light by means of a spatial optical system.

Pump reflectors for use in cladding-pumped fiber systems, such as laser or amplifier systems, are provided. The pump reflector includes an optical fiber segment having at least one core and at least one cladding. A cladding Bragg grating is written by femtosecond inscription in the optical fiber segment, and extending across at least a portion of the cladding. The cladding Bragg grating has a reflectivity profile encompassing the spectral profile of the pump and a spatial profile encompassing the pump spatial distribution in the cladding. A method of manufacturing a pump reflector using femtosecond light pulses is also provided.

A hybrid optical amplifier is proposed that includes a preamplifier element formed of single-clad Ho-doped optical fiber and a power amplifier element formed of single-clad Tm-doped (or Tm—Ho co-doped) optical fiber. The preamplifier is used to impart gain to an input signal propagating at a wavelength λ.sub.S in the presence of a first pump beam operating at λ.sub.P1, creating an amplified output over a defined transmission bandwidth. The power amplifier element is disposed at the output of the preamplifier element and provides an additional level of gain to the output of the preamplifier element in the presence of a second pump beam operating at λ.sub.P2. A passband filter may be used between the preamplifier and the power amplifier to ensure that only wavelength components within the defined transmission bandwidth are applied as an output to the power amplifier.

A planar waveguide amplifier includes a planar waveguide including a flat plate-like core; a first cladding provided on a first principal face of the core; and a second cladding provided on a second principal face of the core, and signal light and pumping light travel into the planar waveguide so that the signal light and the pumping light propagate inside the core in such a manner that optical paths of the signal light and the pumping light overlap each other, and in a zig-zag manner, and the core is an amplification medium containing a rare-earth element serving as an active ion of a three-level system, and absorbs the signal light on the basis of a reduction in intensity of the pumping light.