There is described a fiber laser system generally having a pump laser generating a pump laser beam; and a length of optical fiber optically coupled to the pump laser, the length of optical fiber having: a laser cavity having a cavity path, a first fiber Bragg grating having a first reflectivity profile, a second filter having a second filter profile, and an optical gain region between the first fiber Bragg grating and the second filter along the cavity path, the first reflectivity profile being spectrally detuned from the second filter profile, the first fiber Bragg grating having a first refractive index profile comprising a full width at half maximum bandwidth of at least 0.2 nm and a Gaussian-like apodization, wherein, upon pumping of the optical gain region with the pump laser beam and mode locking of the laser cavity, optical pulses are circulated along the cavity path; and an output.

An array of surface-emitting gain chips includes a common substrate, plural gain chips formed on the common substrate, each configured to generate a light beam, plural optical couplers, each located on a top surface of a corresponding gain chip of the plural gain chips, plural optical fibers, each connected with one end to a corresponding optical coupler of the plurality of optical couplers, an array wide optical coupler connected to another end of the plural optical fibers, and a single optical fiber connected to the array wide optical coupler and configured to output the combined light beams.

An optical resonator may be provided. The optical resonator may comprise a laser system with an adjustable optical path length. The optical resonator may include a back mirror. The back mirror may include a first back mirror surface and a second back mirror surface. The first back mirror surface and may provide a first optical path length for the optical resonator if the first back mirror surface may be included in the optical path. The second back mirror may provide a second optical path length for the optical resonator if the second back mirror surface is included in the optical path.

Examples of the present invention include integrated erbium-doped waveguide lasers designed for silicon photonic systems. In some examples, these lasers include laser cavities defined by distributed Bragg reflectors (DBRs) formed in silicon nitride-based waveguides. These DBRs may include grating features defined by wafer-scale immersion lithography, with an upper layer of erbium-doped aluminum oxide deposited as the final step in the fabrication process. The resulting inverted ridge-waveguide yields high optical intensity overlap with the active medium for both the 980 nm pump (89%) and 1.5 μm laser (87%) wavelengths with a pump-laser intensity overlap of over 93%. The output powers can be 5 mW or higher and show lasing at widely-spaced wavelengths within both the C- and L-bands of the erbium gain spectrum (1536, 1561 and 1596 nm).

Compact optical frequency sources are described. The comb source may include an intra-cavity optical element having a multi-material integrated structure with an electrically controllable active region. The active region may comprise a thin film. By way of example, the thin film and an insulating dielectric material disposed between two electrodes can provide for rapid loss modulation. In some embodiments the thin film may comprise graphene. In various embodiments of a frequency comb laser, rapid modulation of the CEO frequency can be implemented via electric modulation of the transmission or reflection loss of an additional optical element, which can be the saturable absorber itself. In another embodiment, the thin film can also be used as a saturable absorber in order to facilitate passive modelocking. In some implementations the optical element may be formed on a cleaved or polished end of an optical fiber.

A multi-wavelength laser system includes a first fiber laser having a first cavity mirror and a first output coupler, a first optical coupler configured to receive light from the first output coupler, a second fiber laser having a second cavity mirror and a second output coupler, and a second optical coupler configured to receive light from the second output coupler. The multi-wavelength laser system also includes a spectral beam combiner configured to receive first output light from the first optical coupler, receive second output light from the second optical coupler, combine the first output light and the second output light, and form a multi-wavelength output beam.

A ring cavity laser source, a tunable ring cavity laser source and a method of fabricating a ring cavity laser source. The fiber ring cavity laser source comprises a fiber pigtailed pump laser; a fiber-based gain medium; a fiber-based circulator; a fiber-based coupler, wherein an input fiber port of the fiber-based coupler is coupled to a first end of the fiber-based gain medium, a first output fiber port of the fiber-based coupler is coupled to a first fiber port of the fiber-based circulator, and a second output fiber port of the fiber-based coupler is configured for extracting a laser output of the fiber ring cavity laser source; a fiber-based reflector coupled to a second fiber port of the fiber-based circulator; and a fiber-based combiner, wherein a first input fiber port of the fiber-based combiner is coupled to the fiber pigtailed pump laser, a second input fiber port of the fiber-based combiner is coupled to a third fiber port of the fiber-based circulator, and an output fiber port of the fiber-based combiner is coupled to a second end of the fiber-based gain medium; wherein the fiber-based reflector is configured for wavelength tuning of the laser output.

A tunable narrow-linewidth photo-generated microwave source based on polarization control includes a high-reflectivity fiber grating, a high-gain fiber, a low-reflectivity polarization-maintaining fiber grating, a stress adjusting device, a single-mode semiconductor pump laser, an optical wavelength division multiplexer, a polarization beam splitter, a polarization controller, an optical coupler, and a photoelectric detector. Birefringence distribution in the low-reflectivity polarization-maintaining fiber grating is controlled by adjusting a stress magnitude of the stress adjusting device to the low-reflectivity polarization fiber grating, thereby controlling a laser frequency working in different polarization modes in a resonant cavity, and a tunable narrow-linewidth photo-generated microwave source is generated by a beat-frequency technology using a dual-wavelength narrow-linewidth laser with variable frequency intervals.

A CO.sub.2 laser that generates laser-radiation in just one emission band of a CO.sub.2 gas-mixture has resonator mirrors that form an unstable resonator and at least one spectrally-selective element located on the optical axis of the resonator. The spectrally-selective element may be in the form of one or more protruding or recessed surfaces. Spectral-selectivity is enhanced by forming a stable resonator along the optical axis that includes the spectrally-selective element. The CO.sub.2 laser is tunable between emission bands by translating the spectrally-selective element along the optical axis.

A radiation field generating system comprising an optical unit with an optical assembly which defines an optical path is provided, wherein the optical unit is operable in several different operation conditions and the optical assembly comprises at least one optical switching component with which switching between at least two different operation conditions of the several operation conditions can be performed.