Holographic DFB Dye Lasers

A new simple type of DFB dye laser is proposed. The laser consists of a dye cell and a transparent phase holographic grating mounted on the front window of the cell. In the experiment, high-quality stable transparent holographic gratings were recorded in bichromated gelatine with a single mode He-Cd laser. When pumped perpendicular to the surface of the grating the DFB laser emitted a narrow spectral line independently of the width and the position of the pump spectrum. A linewidth of 0·01 nm was measured under pumping with broadband radiation of 20 nm spectral width. Either a set of holographic gratings of a different period or a fan-shaped grating may be used in the laser for stepped or continuous spectral tuning.     

High Efficiency Flashlamps for Pulsed Dye Lasers

This paper discusses the possibilities of pulsed high pressure mercury capillary lamps as efficient pumping sources for dye lasers. Spectral measurements show that a spectral efficiency as high as 24 per cent may be reached for a typical blue lasing dye. Laser action has been obtained with Rhodamine 6G with a repetition rate of up to 100 p.p.s., and an experimental threshold in good agreement with the theoretical one, calculated from the spectra. The life of the lamps has been tested, and no reduction of the luminous output has been observed after ～10⁵ pulses. Severe thermal problems have been encountered with blue lasing dyes, which we hope to solve by using watersoluble coumarins.     

Linewidth-determining Processes in Distributed Feedback Dye Lasers

Abstract

Processes determining the linewidths of distributed feedback dye lasers (DFDL) have been investigated. Time resolution of the frequency of the output pulse shows that the linewidth, averaged over a pulse, arises predominantly from a dynamic sweeping of the laser frequency during the course of the pulse. This sweeping results from refractive-index changes in the dye over the duration of the pumping pulse; either through thermal effects or dispersion associated with the saturated gain. Thermal effects may be minimized by suitable choice of solvent but the dispersive sweep is inherent in this type of laser. The magnitude of the dispersive sweep changes across the tuning range of the laser. By judicious choice of dye solvent and dye parameters we have developed a narrow linewidth DFDL of 140 MHz for τ = 3·2 ns pulses, which is close to the transform limit.     

XUV Lasers

Abstract

Recent dramatic progress worldwide in the development of XUV lasers using laser-produced plasmas as the active media is reviewed, with particular reference to XUV lasers in recombining plasmas being developed by University groups in the U.K. using the SERC's Central Laser Facility.     

Dynamic-single-mode Lasers

Recent progress in the dynamic-single-mode (DSM) semiconductor laser for long wavelength optical fibre communications is reviewed, and applications to wide-band optical fibre communication in the lowest loss wavelength region of 1·5–1·65 μm are studied. A DSM laser consists of a mode selective resonator and a transverse-mode-controlled waveguide, such as the narrow-striped distributed Bragg reflector (DBR) laser, to maintain a fixed axial mode under rapid direct modulation. The technology of monolithic integration for optical circuits is applied to realize some DSM lasers. The structures and properties of DSM lasers are reviewed.     

Dynamic Range Enhancement for Pure Rotational Coherent Anti-Stokes Raman Scattering Thermometry by use of an Optical Arrangement with Two Dye Lasers

A disadvantage of pure rotational coherent anti-Stokes Raman scattering (CARS) compared with vibrational CARS is the limited dynamic range for temperature measurements. Here an optical configuration is described that overcomes this limitation by the use of two different center-frequency dye lasers in a dual-broadband CARS approach. Its performance is demonstrated for simultaneous pure rotational CARS temperature and relative N(2)-O(2)concentration measurements up to 1950 K at ambient pressure.