Abstract: Mode-locked laser comprising an active medium for the emission of a fundatal frequency radiation w1, with a resonator which is defined by a first mirror and a second mirror and in which the active medium is disposed, and a nonlinear optical means which is arranged between the active medium and the second mirror and which in combination with the second mirror effects a preferred reflection of radiation of higher intensity compared with radiation of lower intensity and it converts a fundamental-frequency radiation reversibly into radiation of a first frequency and radiation of a second frequency in such a manner that with increasing intensity the fraction of the radiation of the second frequency increases, and that the second mirror reflects at the second frequency to a greater extent than at the first frequency.

Abstract: An optical interferometric apparatus in which the intensity transmission factor is electrically controllable between at least one radiation beam input and at least one radiation beam output includes an interferometric device with a beam splitter for producing two coherent partial beams which pass via corresponding partial beam paths to a beam combining device where they interfere. In at least one of the partial beam paths there is disposed an electro-optical device in which the optical length of the portion of the partial beam path in question passing through it is electrically changeable, e.g., by means of the refractive index. The partial beams are combined strictly parallel with each other, so that the output beam provided by the beam combining device has a constant phase across its width and the intensity can be varied essentially between the full intensity of the input beam and zero by an appropriate change of the optical path length.

Abstract: A radial or tangential polarization of a beam of light radiation with respect to an optical axis, along which said beam propagates, is effected by causing interaction of the beam with at least one conical interface between a pair of optical media having different indices of refraction. The conical interface(s) may be provided with a polarization-selective coating.

Abstract: An optical laser pumping system comprises means for providing a highly collimated pump radiation beam propagating along an axis, and an optical element which forms a concave, frustro-conical reflecting surface which is coaxial to said axis and tapers in the direction of beam propagation from an entrance end of large cross section, into which said beam enters, to a distal end of small cross section which surrounds said axis in spaced relationship. The laser medium is positioned between said ends along said axis.

Abstract: A method of producing individual short laser pulses in which a stimulatable laser medium is excited by a pump pulse in order to produce a population inversion above a laser threshold value, the population inversion being kept below the threshold value after emission of the short radiation pulse. The laser medium is common to two resonators and from it energy in the form of the desired individual short laser radiation pulse is first taken from the first resonator by means of a first relaxation process of given threshold value, relatively short time constant and relatively low quality factor, after which the inversion in the laser medium is kept below the preset threshold value of the first resonance process by a second relaxation process of relatively long time constant and relatively high quality factor in the second resonator coupled to the first.

Abstract: In a method and an apparatus for generating a hot plasma which emits elecmagnetic radiation in the wavelength range below about 100 nm in a predetermined volume, in which a laser radiation pulse of short duration with sufficient energy and power density is focused into the volume containing a target material, the laser radiation energy which is necessary for generating the plasma emitting the radiation is radiated into the target volume by a focused laser radiation pulse which is shorter than one picosecond. The method may be used in ASE X-ray laser comprising an axicon focusing optics.

Abstract: Ultra-short individual laser pulses, having a half-amplitude duration of 100 picoseconds or less and a recurrence frequency of one Hz to one mHz are generated in a self Q-switching distributed feedback dye laser that employs a high density diffraction grating as a beam divider, dividing a primary beam from a pulsed pump laser into two excitation beams of +1 and -1 order; the excitation beams are directed, by two reversing mirrors, to impinge upon a focal line in a dye solution serving as an active laser medium. The pulses of the primary beam have a half-amplitude duration many times greater than 100 psec but no greater than 20 nsec, and the beam intensity is such that the stimulation of the dye does not exceed its laser threshold by more than 20%.

Abstract: A method of photochemical separation of isotopes, wherein molecules containing differing isotopes to be separated are selectively excited by laser radiation, and the excited molecules are collectively reacted with a scavenger which is relatively inert to molecules of lesser excitation, the reaction producing a stable addition product which is readily isolatable.

Abstract: A display process for the optical presentation of information which process omprises impinging laser beams modulated as to their direction, intensity and/or frequency, upon a transparent target containing a fluorescent substance which is excited by said laser beams to optical fluorescence, e.g., which absorbs in the ultraviolet range and yields fluorescent radiation in the visible range; typical ions capable of fluorescence are uranyl ions or ions of the rare earth elements.

Abstract: Novel dyestuffs comprising at least one laser dyestuff radical and at least one fluorescent dyestuff radical, where the fluorescent range of the fluorescent dyestuff radical overlaps the absorption range of the laser dyestuff radical and is linked with the laser dyestuff radical directly or via a bridge member having a length of at most 20 A in such a manner that the .pi. electron systems of the individual radicals are decoupled, are outstandingly effective and long lived when used in dyestuff lasers. The dyestuffs can be of the formula:X--(CR.sub.1 R.sub.2).sub.n --X--[(CR.sub.1 R.sub.2).sub.n --X].sub.mwhereinN is 0 or an integer from 1 up to a number corresponding to a chain length of 20 A,m is 0, 1, 2 or 3,X is a laser dyestuff radical L or a fluorescent dyestuff radical F andR.sub.1 and R.sub.