Search

Unlike other drive fusion class laser, Megajoule laser (LMJ) and its first prototype, the Laser Integration Line (LIL) are equiped with specific diffractive optical components. All these optics are situated in the final optic assembly. An high efficiency diffraction focusing grating called 3w grating is used to focus the beam into the center of the target chamber instead of a classical focusing lens. Another large grating called 1w grating is used for optical path compensation purposes. Both gratings have a dimension of 420x470mm 2 and are working at an incidence of 25°. Gratings are plano transmission holographic gratings directly engraved into fused silica substrates. The 1w grating is working at the wavelength of 1.053μm, its grooves are straight and equispaced. The 3w grating, is a focusing grating working at the wavelength of 0.351μm. Its grooves are curved and non equispaced. Jobin Yvon was selected by CEA to manufacture these two types of diffraction graintgs. After processes developpements and facilitization, a complete batch of twelve 1w gratings and sixteen 3w gratings were delivered to CEA for integration. After a brief presentation of CEA's specification for this diffractive components, we give some details on the manufacturing processes. We also demonstrate good agreement between specified and manufactured component. We give an overview of the global production performances

The Megajoule laser (LMJ) and its first prototype, the Laser Integration Line (LIL), is equipped with a specific final optics assembly involving two diffraction gratings instead of a classical focusing lens. Both gratings have a dimension of 420 X 470 mm 2 and are working at an incidence of 25 degree(s).. Gratings are plano transmission holographic gratings directly engraved into fused silica substrates. The 1(omega) grating is working at the wavelength of 1.053 micrometers , its grooves are straight and equispaced. The 3(omega) grating, is a focusing grating working at the wavelength of 0.351 micrometers . Its grooves are curved and non equispaced. The gratings were designed and manufactured to present efficiencies superior to 90% on the whole clear aperture and an improved damage threshold. After Jobin Yvon's selection by CEA in 1999, specific equipment and facilities were put in place to manufacture these large gratings. The aim of this contribution is to present the early results of the development of this 1(omega) and 3(omega) gratings. After a short introduction to the 1(omega) and 3(omega) gratings specifications, manufacturing process, efficiencies result and AFM profiles of the first manufactured gratings will be detailed.

To deviate and focus of the beams of the future Laser Integration Line (LIL) and Megajoule laser (LMJ), CEA has chosen an original setup using two large 420 x 470 mm2 transmission gratings. The first grating is an holographic plano transmission master grating with straight and equispaced ruling, 25 degree(s) incidence angle and working at 1.053 micrometers . The second one is an holographic plano transmission master grating, with curved and non equispaced ruling, 25 degree(s) incidence angle which combines both focusing and deviation properties. Groove profile of both gratings is deep laminar. High damage threshold, improved wavefront quality and high efficiencies are the main issues for those two gratings. Jobin Yvon's was selected by CEA in 1999 to develop, industrialize and manufacture gratings reaching LIL/LMJ specifications. A dedicated plant and facilities were built to manufacture the gratings directly engraved into the fused silica substrates provided by CEA. After process developments, Jobin Yvon manufactured the two first 1(omega) and 3(omega) gratings in mid 2001. After a short summary of the specification of these gratings, we present in this paper the production process and the performances of the 1(omega) and 3(omega) gratings manufactured. Wavefront data, efficiency measurements and damage threshold performances are detailed.

To focus the third harmonic of high energy neodymium glass laser, the usage of focusing transmissions diffractive gratings ion etched directly into fused silica blank brings major benefits in comparison with classical optical solutions using aspheric lenses. The damage threshold of such a diffractive component is the same as the damage threshold of a high grade, thin, fused silica plane window. The transmission efficiency reaches 94 percent for polarization s or p. The image quality is nearly perfect: this diffractive component acts as a stigmatic lens. It separates the remaining first and second harmonic from the third one and in addition it creates a focused reflective order with 0.5 percent efficiency which offers the possibility to get a well focused sampling beam.

Variable line space (VLS) diffraction gratings present interesting solutions to design high resolution monochromators for synchrotrons. The problem is to be able to record holographically the desired grooves distribution in order to take advantage of the holographic recording and ion etching process: low stray light, absence of ghosts and second order reduction. We will review the method of calculation of VLS diffraction gratings recorded holographically by using spherical and aspherical laser wavefronts. Then the manufacture of these gratings (accuracy of recording and ion etching process) will be described. We will give an example. And finally, the theory and the accuracy of a checking method will be presented.

We call "monograph" a spectrometer which can work as well as a spectrograph or as a monochromator. The system has been designed to allow time resolved spectroscopy on hot laser excited plasmas by using a slit camera and either a single or a multichannel detector. The mounting derives from a plane grating monochromator (PGM) configuration, which associates a toroidal mirror and a plane holographic grating with non uniform groove distribution to allow optimum aberration correction. The mirror and the grating work at nearly the same deviation angle in a compensated manner which gives an "in line" configuration.

We have designed and manufactured a new concave, flat field, grating which permits to disperse simultaneously several spectra onto a matrix detector without any crosstalk between spectra and with a good resolution. Applications include absorption spectrophotometers, liquid chromatography detectors, blood analysers, colour measurement systems, etc... This paper describes the optimization and the performances of such a grating manufactured for being included in a blood analyser.