A mode control system and method for controlling an output mode of a broadband radiation source including a photonic crystal fiber (PCF). The mode control system includes at least one detection unit configured to measure one or more parameters of radiation emitted from the broadband radiation source to generate measurement data, and a processing unit configured to evaluate mode purity of the radiation emitted from the broadband radiation source, from the measurement data. Based on the evaluation, the mode control system is configured to generate a control signal for optimization of one or more pump coupling conditions of the broadband radiation source. The one or more pump coupling conditions relate to the coupling of a pump laser beam with respect to a fiber core of the photonic crystal fiber.

In a terahertz wave generation apparatus including a first non-linear optical crystal 3 on which first laser L1 and second laser L2 from laser generation means 2 are incident to generate terahertz wave TH1, the laser generation means includes a second non-linear optical crystal 7 on which laser having the same wavelength as that of the second laser is incident to generate idler light L1 including a plurality of wavelengths, and makes the idler light L1 generated from the second non-linear optical crystal incident on the first non-linear optical crystal as the first laser L1, to generate terahertz wave including a plurality of wavelengths from the first non-linear optical crystal 3, and wavelength selection means including a transmission section which transmits an idler light having the specific wavelength in the idler light including the plurality of wavelengths can be provided, as needed. Thus, terahertz wave having a high output power and including a plurality of wavelengths can be obtained, and the wavelength selection means easily obtains a required terahertz wave having the specific wavelength.

A MOPA laser system that includes a seed laser configured to output pulsed laser light, an amplifier configured to receive and amplify the pulsed laser light emitted by the seed laser; and a pump laser configured to deliver a pump laser beam to both the seed laser and the amplifier.

The invention relates to a device (2) and to a method for characterizing an ultrashort laser pulse. Furthermore, the invention relates to use of a self-contained optical assembly in a device (2) for characterizing an ultrashort laser pulse. The device (2) comprises an imaging optical element (4) configured to image the incident laser pulse (6) in a direction of a straight line (L). A first optical element (10) is configured to apply predetermined varying group delay dispersion on the line focused laser pulse. A non-linear optical element (14) is configured to generate a second harmonic laser pulse (30). An optical grating (20) generates a diffraction of the second harmonic laser pulse, which is imaged on a flat sensor (24). A processing unit (36) determines a best fit for the captured image thereby calculating a frequency spectrum and a spectral phase of the laser pulse.

The present application discloses a nonlinear optical crystal material, preparation method and application of the nonlinear optical crystal material. The nonlinear optical crystal material has an excellent infrared nonlinear optical performance, whose frequency-doubling intensity can reach 9.3 times of AgGaS.sub.2 with the same particle size, and it meets type-I phase matching; and its laser damage threshold can reach 7.5 times of AgGaS.sub.2 with the same particle size. The nonlinear optical crystal material has important application value in the frequency-converters which can be used for frequency doubling, sum frequency, difference frequency, optical parametric oscillation of laser in mid and far infrared waveband, and the like.

A fiber structural body includes a first fiber, and a second fiber spliced to the first fiber such that light having propagated through the first fiber propagates through the second fiber. At least one of the fibers is a photonic crystal fiber. The second fiber is coated with a first coating layer and a second coating layer in order from a splice surface, and the first coating layer has a refractive index n.sub.1 larger than that of a clad layer of the second fiber. In the fiber structural body, L, r, n.sub.1, and NA satisfy a particular relationship.

Embodiments of the invention provide apparatuses and methods for generating frequency combs. A non-linear optical medium may generate new optical waves centered at frequencies differing from the input waves, while retaining the input wave properties. In the case when a parametric mixer is used to generate frequency combs with small frequency pitch, the phase correlation of the input (seed) waves can be achieved by an electro-optical modulator and a single master laser. In the case when a frequency comb possessing a frequency pitch that is larger than frequency modulation that can be affected by an electro-optic modulator, the phase correlation of the input (seed) waves is achieved by combined use of an electro-optical modulator and injection locking to a single or multiple slave lasers.

There is provided a laser system that may include a Raman cell, a pumping light generator, and a Raman cell laser unit. The pumping light generator may include one or more optical parametric amplifiers (OPAs), and may be configured to output first Raman-cell pumping light and second Raman-cell pumping light to the Raman cell. The Raman cell laser unit may be configured to output probing light as a target of wavelength conversion to the Raman cell.

The present invention provides a burst-laser generator using an optical resonator which produces high pulse-strength of burst-laser in order to conduct laser Compton scattering, comprising: a self-oscillation amplifying optical loop-path and an external optical resonator to burst-amplify laser, wherein, laser supplied by an exciting laser source is self-oscillation amplified with the self-oscillation amplifying optical loop-path and further burst-amplified with the external optical resonator.

A broadband light source device for creating broadband light pulses includes a hollow-core fiber and a pump laser source device. The hollow-core fiber is configured to create the broadband light pulses by an optical non-linear broadening of pump laser pulses. The hollow-core fiber includes a filling gas, an axial hollow light guiding fiber core configured to support core modes of a guided light field, and an inner fiber structure surrounding the fiber core and configured to support transverse wall modes of the guided light field. The pump laser source device is configured to create and provide the pump laser pulses at an input side of the hollow-core fiber. The transverse wall modes include a fundamental transverse wall mode and second and higher order transverse wall modes.