A wavelength selection method for a tunable laser includes: obtaining a target wavelength; and calculating target resistance values of two thermistors, respectively, corresponding to the target wavelength. Each of the two thermistors is used to monitor the temperature of a corresponding one of two wavelength selection components. Each of the target resistance values is calculated according to a relationship between a wavelength drift and a resistance change of the corresponding thermistor and according to an initial wavelength and an initial resistance value of the corresponding thermistor corresponding to the initial wavelength. The method further includes: heating the two wavelength selection components to control their temperatures until real-time resistance values of the two thermistors reach the target resistance values, respectively; and stabilizing the real-time resistance values at the target resistance values and outputting a laser beam having the target wavelength.

A fiber laser device includes a pumping light source, an amplifying fiber, an input side fiber fusion-spliced on an input side of the amplifying fiber and formed with a HR-FBG, an output side fiber fusion-spliced on an output side of the amplifying fiber and formed with an OC-FBG having a reflectivity smaller than that of the HR-FBG, an output end, and a mode filter, wherein the input side fiber or an intermediate fiber disposed between the amplifying fiber and the input side fiber is fusion-spliced with the amplifying fiber via a fusion splice portion, and at least a portion of the mode filter is disposed in a region between the fusion splice portion and a position separated from the fusion splice portion by a coherence length of beating caused by mode interference of signal light propagating in the amplifying fiber.

An active element-doped optical fiber includes a core that includes a first region and a second region. The first region satisfies 0≤r≤0.65d, and the second region surrounds the first region and satisfies 0.65d<r≤d, where d is a radius of the core and r is a distance from a central axis of the core in a radial direction. At least a part of the first region is doped with an active element excited by excitation light, the second region is not doped with the active element, and a shape index is 0.99 or more and less than 1.

A laser device includes: a traveling wave type resonator comprising a first mirror and a second mirror; and a laser medium disposed between the first mirror and the second mirror. The first mirror and the second mirror are disposed such that round-trip light that travels in round trips in the resonator has a focus inside the laser medium. The laser device is configured such that: excitation light incident on the resonator is superimposed on the round-trip light at the focus and narrowed to be thinner than the round-trip light, Z.sub.R×α<0.5 is satisfied, where Z.sub.R is a Rayleigh length of the excitation light and α is an absorption coefficient of the laser medium with respect to the excitation light, and a round-trip Gouy phase shift of the resonator has a value excluding 2π×n/m where m is an integer of less than 15 and n is an integer of equal to or less than m.

A multi-clad optical fiber is provided. The fiber includes, concentrically and radially outwards from the center of the optical fiber, a core doped with at least one rare-earth dopant material, a pedestal cladding structure, an inner cladding and an outer cladding. The pedestal cladding structure includes a pedestal layer having a refractive index smaller than a refractive index of the core, and a raised index layer having a refractive index larger than the refractive index of the pedestal layer. The raised index layer has a thickness and a refractive index which preserve the confinement of the core mode in the core and minimize the overlap of one or more pedestal modes with the core.

A system includes a planar waveguide that includes an active gain medium configured to receive pump light from a pump source and amplify stimulated emission light. The planar waveguide has a fast axis and a slow axis and is configured to operate in single mode in the fast axis and multimode in the slow axis. The system also includes a hybrid spatial filter configured to receive the amplified stimulated emission light from the planar waveguide and output laser light. The hybrid spatial filter includes a physical slit having a narrower dimension corresponding to the slow axis of the planar waveguide. The physical slit is configured to reduce an intensity of the amplified stimulated emission light received from the planar waveguide. The hybrid spatial filter also includes a Volume Bragg Grating (VBG) configured to constrain an angle of the amplified stimulated emission light and enable compact geometry intra-cavity beam expanding/collimating optics.

A system includes a seed laser configured to generate a seed beam and multiple arrays of semiconductor diode lasers configured to generate multiple pump beams. The system also includes a Raman amplifier having a core, a first cladding around the core, and at least a second cladding around the first cladding. The core is configured to amplify the seed beam based on optical pump power provided by the pump beams. Each of the core, the first cladding, and the second cladding includes fused silica, and at least the core and the first cladding are doped. The core has a numerical aperture of approximately 0.06 or less and a diameter of approximately 20 μm to approximately 25 μm. The first cladding has a numerical aperture of approximately 0.17 or less and a diameter of approximately 35 μm to approximately 45 μm.

A method and system for combining two or more optical fields is disclosed. A first continuous-wave high powered output field generated by a solid-state master laser is injected into a first solid state optical amplifier to produce a single output field from the laser system that exhibits a high phase-coherence with the output field of the master laser. The power of the output field equals the sum of powers of the master laser and that generated by the first optical amplifier, while exhibiting similar beams characteristics to that produced by the output field of the master laser i.e. it exhibits low noise, in a single transverse and longitudinal mode Gaussian beam, and has a single polarisation. The laser system is highly scalable in that N optical amplifiers may be located in series with the master laser to provide a single low noise, high power output field.

Systems and methods described herein provide a thermally compensated waveguide structure having a thermal index profile configured to correct thermal aberrations caused by temperature gradients in a fast axis direction and/or correct other forms of distortions in an output beam generated by the waveguide structure. The waveguide structure includes a core region, one or more cladding, and one or more heat sinks. A geometry of these portions with respect to each other can provide a cold refractive index profile such that a cold refractive index value of a portion of the core region is less than a cold refractive index value of at least one of the one or more cladding regions. Responsive to thermal compensation, the cold refractive index profile is modified, through addition of a thermal index profile, to form a hot index profile having attributes including good overlap of the fundamental mode with the gain profile and mode clean-up through gain discrimination against higher order modes.

Techniques for producing a Brillouin laser are provided. According to some aspects, techniques are based on forward Brillouin scattering and a multimode acousto-optic waveguide in which light is scattered between optical modes of the waveguide via the Brillouin scattering. This process may transfer energy from a waveguide mode of pump light to a waveguide mode of Stokes light. This process may be referred to herein as Stimulated Inter-Modal Brillouin Scattering (SIMS). Since SIMS is based on forward Brillouin scattering, laser (Stokes) light may be output in a different direction than back toward the input pump light, and as such there is no need for a circulator or other non-reciprocal device to protect the pump light as in conventional devices.