A laser device includes a first laser medium and a second laser medium that have a first surface and a second surface opposite to the first surface, and receive input of excitation light and seed light from the first surface side to amplify the seed light, a holder that holds the first laser medium and the second laser medium; and a pair of cooling units that cool the first laser medium and the second laser medium according to change in volume of a refrigerant.

A laser device includes a first laser medium and a second laser medium that have a first surface and a second surface opposite to the first surface, and receive input of excitation light and seed light from the first surface side to amplify the seed light, a holder that holds the first laser medium and the second laser medium; and a pair of cooling units that cool the first laser medium and the second laser medium according to change in volume of a refrigerant.

A semiconductor laser source including a Mach-Zehnder interferometer, this interferometer including first and second arms. Each of the arms is divided into a plurality of consecutive sections, the effective index of each section located immediately after a preceding section being different from the effective index of this preceding section. The lengths of the various sections meet the following condition: $\underset{n=1}{\overset{N_2}{.Math.}}{L}_{2,n}{\mathrm{neff}}_{2,n}-\underset{n=1}{\overset{N_1}{.Math.}}{L}_{1,n}{\mathrm{neff}}_{1,n}=k_f{\lambda }_{\mathrm{Si}}$
where: k.sub.f is a preset integer number higher than or equal to 1, N.sub.1 and N.sub.2 are the numbers of sections in the first and second arms, respectively, L.sub.1,n and L.sub.2,n are the lengths of the nth sections of the first and second arms, respectively, neff.sub.1,n and neff.sub.2,n are the effective indices of the nth sections of the first and second arms, respectively. The first and second arms each comprise a gain-generating section.

A semiconductor laser source including a Mach-Zehnder interferometer, this interferometer including first and second arms. Each of the arms is divided into a plurality of consecutive sections, the effective index of each section located immediately after a preceding section being different from the effective index of this preceding section. The lengths of the various sections meet the following condition: $\underset{n=1}{\overset{N_2}{.Math.}}{L}_{2,n}{\mathrm{neff}}_{2,n}-\underset{n=1}{\overset{N_1}{.Math.}}{L}_{1,n}{\mathrm{neff}}_{1,n}=k_f{\lambda }_{\mathrm{Si}}$
where: k.sub.f is a preset integer number higher than or equal to 1, N.sub.1 and N.sub.2 are the numbers of sections in the first and second arms, respectively, L.sub.1,n and L.sub.2,n are the lengths of the nth sections of the first and second arms, respectively, neff.sub.1,n and neff.sub.2,n are the effective indices of the nth sections of the first and second arms, respectively. The first and second arms each comprise a gain-generating section.

A radio-frequency, RF, slab laser 10 with a Z-fold resonator cavity defined by an output mirror 32, a first fold mirror 34, a second fold mirror 36 and a rear mirror 30. The second fold mirror 36 is rotated by an adjustment angle away from the angle it would have if the mirrors were all plane mirrors and directed the round trip beam path by direct reflection. Moreover, the rear mirror 30 is rotated by an adjustment angle that is approximately twice the adjustment angle of the second fold mirror 36. These rotations of the rear mirror 30 and second fold mirror 36 suppresses parasitic mode paths that would otherwise exist.

A system includes a heat sink module and a driving circuit module. The heat sink module includes stepped through-holes that each includes a cylindrical upper and lower portions connected by a ring-shaped surface. The bottom surface of the heat sink module includes grooves that respectively pass through the lower portions of respective sequences of the stepped through-holes. The driving circuit module includes conductive connectors and electrical driving surfaces that are disposed external to the heat sink module. Each conductive connector lies within a respective groove in the bottom surface of the heat sink module. The conductive connectors include internal connectors that each link at least two stepped through-holes in a respective sequence of stepped through-holes passed by a respective groove, and include external connectors that each link at least one stepped through-hole in the respective sequence of stepped through-holes to the electrical driving surfaces.

A spectral beam combining system includes a plurality of input fibers and a prism having a curved input surface. The plurality of input fibers are attached to the curved input surface. The spectral beam combining system also includes an immersion grating defined on a second surface of the prism, a protective cap disposed over the immersion grating, and an output surface.

A spectral beam combining system includes a plurality of input fibers and a prism having a curved input surface. The plurality of input fibers are attached to the curved input surface. The spectral beam combining system also includes an immersion grating defined on a second surface of the prism, a protective cap disposed over the immersion grating, and an output surface.

A method or apparatus for narrowing the linewidth of a single mode laser is provided. The linewidth of a single mode laser is narrowed by injecting an optical feedback simultaneously into the first laser cavity mirror and the second laser cavity mirror of the single mode laser.

A continuous optical beat laser element for generating terahertz (THz) waves and a laser source using same includes periodically poled lithium niobate (ppLN) crystals arranged along a predetermined direction forming a surface generally parallel to the predetermined direction. A Ti diffused region is applied on the surface and an array of gold nanowires are applied on the Ti diffused region to form a gold metal-insulator-metal (MIM) element that optimizes coupling and channeling of THz radiation from the crystals into the gold nanowires. The system provides a simple, stable, compact and cost-effective THz source using a widely tunable C-band SOA-based laser to excite a non-linear photo-mixer to produce terahertz radiation that ranges from 0.8 to 2.51 THz at room temperature. This laser source can be modified into an all fiber-based THz generator by embedding ppLN crystals in a fiber filament configuration resulting in less absorption and producing high output power.