The optical cavity of the present laser has a folded optical path with a pair of reflective diffraction gratings and a gain cell in it. A disk with radially distributed perforations rotates in the optical path between the gratings and the gain cell. The laser wavelength depends upon which perforation is aligned with the slot in a slotted plate also in the optical path. The laser output consists of a sequence of different wavelength but colinear rays.

Laser for providing rapid sequence of different wavelengths

Unstable resonators with 90° beam rotation are discussed. Geometric properties of the forward and reverse modes are derived, and diffractive-optical properties are described. An equation for the equivalent Frensel number is obtained. Plots of eigenvectors of the resonator integral equation are included, and the equivalence of these resonators to a type of strip resonator is established.

Unstable resonators with 90° beam rotation

The laser synchrotron source (LSS) utilizes a high peak power or high average power laser to generate within a vacuum chamber a laser beam travelling in one direction to interact with an electron beam traveling in an opposite direction in order to generate high-power x-rays. A ring resonator formed by a plurality of mirrors directs the laser beam in a closed loop to impact with the electron beam to produce x-rays. Concave mirrors in the ring resonator focus the laser beam upon the point where the laser beam interacts with the electron beam to intensify the laser energy at that point. When a radio frequency linear accelerator (rf linac) is used to produce the electron beam, x-rays having a short pulse length are generated. When a betatron is used as an electron source, x-rays having a long pulse length are generated.

Laser synchrotron source (LSS)

Disclosed is a gas laser utilizing radio frequency discharge excitation in the area of sonic or supersonic/subsonic transfer gas flow. The laser uses various types of gases and mixtures of gases as the active medium and provides for RF or UV pre-ionization of the gaseous medium before using radio frequency discharge excitation. The gas is supplied into a receiver (3a), and has downstream therefrom a supersonic nozzle (1) for acceleration of the active gaseous flow to high subsonic or supersonic speeds in order to provide intensive dynamic cooling of the active gas medium. The gas is excited using radio frequency discharge excitation in the critical area (1b) of the supersonic nozzle or downstream therefrom. The radio frequency discharge and excitation can also occur within the optical resonator region (23) which is located within the supersonic area of the nozzle. The present invention provides compact, efficient and super-powerful continuous, quasi-continuous and pulse laser systems with wavelengths from 2.03 mkm to 10.6 mkm with a high quality output beam. The present laser device may be utilized in scientific, commercial, aerospace and free space applications.

Supersonic and subsonic laser with RF discharge excitation

A technique for increasing the temporal resolution of the optical pulses white simultaneously increasing the spectral resolu-tion of the pulse train in a free-electron laser. The increase in temporal resolution is achieved by introducing a quadratic temporal phase variation (i.e. linear frequency chirp) across the optical pulses, and then propagating the outcoupled pulses through a dis-persive delay line such as a grating pair or prism pair in order to compress them to the transform limit of the broadened spec-trum. Essentially, the quadratic time dependence of the optical phase broadens the spectrum and yields Fourier components whose phase exhibits a quadratic frequency dependence. To operate a free-electron laser in such a configuration, electron micro-pulses with a linear time-dependent energy are produced in the RF linac by positioning the bunches slightly off the peak of the RF wave at phases where the field gradient is large. These electron micropulses are injected into the wiggler and lead to the for-mation of optical pulses with a corresponding linear time-dependent frequency.

Free-electron laser oscillator for simultaneous narrow spectral resolution and fast time resolution spectroscopy

Effects of misalignment of rectangular‐cross‐section unstable resonators are investigated by calculations of eigenvalues and shapes of transverse modes of empty strip resonators. Small misalignments can substantially affect mode‐loss separation. A design criterion is suggested for choice of Fresnel numbers such that effects of misalignments are minimized.

Effects of small misalignments in empty unstable resonators

large optical cross sections using e-beam controlled discharges in CO2 and very recently6 with uv initiation of self-sustained discharges. Principal differences between these two methods are in the spatial variations of electron production for the e-beam and the difficulty in obtaining large optical aperture without arc development for the self-sustained discharge. This paper presents a closed form method for rapidly analyzing and predicting e-beam controlled discharges while accounting for the spatial variations of electron production. Predictions obtained from this method are compared to experimental measurements. The e-beam controlled discharge7'10 has been analyzed for CO2 gas mixtures at 1 atm pressure. Previous analytical methods required considerable computer time because they were based on Monte Carlo7'13 calculations for electron scattering to determine spatial source functions of electron energy disposition. Fixed sets of laser cavity configurations, gas compositions, and densities have been successfully modeled. A new and fast computational method for describing the spatial variations of electron energy disposition in e-beam controlled discharges has been developed. Primary electron range enhancement or de-enhancemen t effects are included, but backscattering and electron-runaway effects are neglected. Spatial variations in the resulting drift current density and applied field are easily determined using the "streamtube" continuity approximation.9 Experiments using a 10-1 discharge volume controlled by a 0.4 A/cm2, 175 kV ebeam were conducted to derive data for correlation. Experimental values of the effective recombination rate, the e

e-Beam Spreading and Resulting Field Variations in CO2 Laser Plasmas

Tilted spherical mirrors are used as a means of achieving asymmetric magnification (M x ≠M y ) in collimated-output unstable resonators which obviate fabrication difficulties associated with non-spherical mirrors. By suitable choice of rather large tilt angles of spherical mirrors and mirror separation, simultaneous "confocality" can be achieved in x-z and y-z planes to the lowest order.

Unstable optical resonators with tilted spherical mirrors

A radio frequency linear acceleration free electron laser is provided by ing the pulses in such a time delay manner to phase lock the device and produce phase correlation between the laser pulses.

Phase locked RF linac free electron laser

An electroadiabatic laser wherein a plenum chamber is provided in which a thermally heated gas is mixed with a relatively cold gas to provide lasing action. An alkali metal compound is mixed simultaneously with the gases to provide additional stimulation of the ionized gases by releasing additional electrons during mixing of the gases. The expanding gases pass through a nozzle into an excitation chamber wherein the gas flows through a magnetic field between two electrodes, generating a current in an electrode load circuit that is identical to the electron flow in the ionized gases. The flowing gases are further expanded through another nozzle into a larger cavity. A pair of electrodes in the second nozzle have an electric field thereacross for further stimulation of the lasing gas. Lasing action of the gas occurs in the larger cavity, a Fabry-Perot optical cavity, and the output therefrom is coupled out of the cavity by mirrors mounted therein. The gases are then exhausted through a diffuser to atmospheric pressure. A magnet provides the magnetic field in the excitation chamber. The excitation chamber electrode load circuit may be connected to provide the potential across the nozzle electrodes, thus using only the field produced by the magnet to generate the additional potential for further stimulated emission.

James F. Perkins

Papers

Effects of small misalignments in empty unstable resonators

e-Beam Spreading and Resulting Field Variations in CO2 Laser Plasmas

Unstable optical resonators with tilted spherical mirrors

Phase locked RF linac free electron laser

Self-pumped electroadiabatic laser