Abstract: The invention relates to a semi-conductor optical amplifier insensitive to the polarization of light. The active layer (20) of this amplifier is made up of an alternating series of solid sub-layers alternately under tensile stress (21) and compressive stress (22) and having the same forbidden band-width. The sub-layers under tensile stress (21) favour the propagation of the TM mode of polarization of light and the sub-layers under compression (22) favour the propagation of the TE mode of polarization of light. In addition, the thicknesses of the sub-layers have values which ensure equal gains G(TE) and G(TM) for the active layer.

Abstract: A stack of optically contacted birefringent crystals is configured to carry out coherent beam combination (multiplexing) of narrow-bandwidth phase-locked beams from multiple lasers or laser amplifiers (e.g., multimode Yb-doped fiber amplifiers). A stack of N crystals can multiplex the output of 2N laser amplifiers into a single diffraction-limited beam. Phase control of the beams is maintained by an electronic servo which monitors the optical power emitted into certain undesired beams and minimizes this power by means of phase adjusters (e.g., piezoelectric fiber stretchers) on each amplifier. A configuration is described where a front-end laser master oscillator (FMO) (e.g., a Nd:YAG laser) is demultiplexed by the crystal stack, passes through multiple laser amplifiers, is reflected back through the amplifiers by phase-conjugating mirrors (e.g., passive multimode fibers generating stimulated Brillouin scattering), and is multiplexed on the return trip through the crystal stack.

Abstract: An optical fiber amplifier having constant output power for each channel including a first measuring unit for dividing an input light signal into a first light signal and a second light signal, sub-dividing the first light signal into a plurality of light signals and converting the plurality of light signals into electrical signals to output the electrical signals, an optical fiber amplifying unit for amplifying the second light signal according to a predetermined amplification control value, a second measuring unit for converting a light signal of a predetermined wavelength band, output from the optical fiber amplifying unit, into an electrical signal, and an output power controller for controlling the predetermined amplification control value according to a plurality of output values of the first measuring unit and an output value of the second measuring unit, so that the power level of the optical fiber amplifying unit is maintained at a constant level.

Abstract: An ignition feedback regenerative amplifier consists of an injector, a linear accelerator with energy recovery, and a high-gain free electron laser amplifier. A fraction of the free electron laser output is coupled to the input to operate the free electron laser in the regenerative mode. A mode filter in this loop prevents run away instability. Another fraction of the output, after suitable frequency up conversion, is used to drive the photocathode. An external laser is provided to start up both the amplifier and the injector, thus igniting the system.

Abstract: The all-optical pulse generating and amplifying system utilizes a phosphor that is excited by input light of a first wavelength and, in response, emits light of a second wavelength. The light emitted by the phosphor illuminates a bistable element which, at a pre-fixed intensity of the phosphor-emitted light, switches from non-transmissive state to transmissive state, thereby allowing the exit of light (also of first wavelength) emitted by an output light source as light pulse output of the system. An inhibitory light that also passes through the bistable element during its transmissive state quenches the phosphor light emission and returns the bistable element to its non-transmissive state and re-starts the process toward the next transmissive state. By gating the intensity, via selected non-linearity of the bistable element, of the light output in proportion to the intensity of the input light, the system can also function as an amplifier.

Abstract: An optical amplifier which suppresses the occurrence of a nonlinear optical phenomena, such as four-wave mixing. The optical amplifier includes an optical fiber doped with a rare earth element, and a light source providing excitation light to the fiber so that a wavelength division multiplexed (WDM) light is amplified as the WDM light travels through the fiber from a first point to a second point along the fiber. A third point exists along the fiber between the first and second points at which a power of the WDM light substantially reaches a level producing a nonlinear optical phenomenal. A first portion of the fiber is between the first point and the third point, and a second portion of the fiber is between the third point and the second point. The second portion suppresses the occurrence of the nonlinear optical phenomena as compared to the first portion. The second portion can have various different constructions to provide the required suppression effect.