SPECTRO Produces 20000. Diffraction Gratings

Friday, March 10, 2000

Kleve, March 10, 2000. The spectrometer manufacturer SPECTRO Analytical Instruments reports an extraordinary landmark: the production of its 2000th diffraction grating. A diffraction grating is an optical component built into spectrometers to disperse the light emitted by various elements into individual wavelengths. In this way, the specific wavelengths of the analyzed elements can be precisely recorded and qualitatively evaluated.

SPECTRO produces 20 different grating types, distinguished by their physical size and more importantly, by the number of grooves/mm - the grating frequency - and the optimum wavelength range. Spectrometer resolution is dependent on the grating frequency - which for SPECTRO gratings lies between 1200 and 3600 grooves/mm. The 2000th grating has 2924.8 grooves/mm and is recorded on a 63.5 mm diameter concave blank. This type of grating is used in the company's new ICP spectrometer - SPECTRO CIROS CCD.

SPECTRO manufactures exclusively original gratings - no replicas (i.e. copies). Each grating undergoes a quality check in test equipment developed by the company. Grating efficiencies in the wavelength range of 120-800 nm can be so measured. In-house production of gratings has clear advantages for the company. All gratings are tailor-made for SPECTROs analytical instruments. New development and optimization can be accomplished in a short time - often within a week. Constant high quality of all gratings is assured.

SPECTRO manufactures holographic diffraction gratings, where laser beams are used to record the groove pattern in a photo resist layer coated on the substrate surface. Subsequently the grating surface is vacuum coated with an aluminum layer. The substrates are made from Zerodur, an extremely stable glass-ceramic material.

World-wide only some 10 companies manufacture such gratings. As far as a concave - Rowland Circle - spectrometer gratings are concerned, SPECTRO produces the largest number in the world - some 20000 gratings in 1999. Production started in 1988. In only three months, the physicist Alexander Termanis could present the first SPECTRO manufactured diffraction grating. There were quite a few obstacles to overcome as parts of the production equipment were not available on the market - necessitating in-house design and manufacture.

Clean-room conditions are required to produce gratings. The delicate grating surfaces, with groove spacings under 1/1000 mm, can be badly blemished by the presence of dust particles. The production laboratory is kept constant within 0.5° C. Mechanical stability is ensured through the use a 2.2 ton granite composite optical table supported on pneumatic anti-vibration mounts, the whole placed on a concrete foundation reaching 1 m below ground.

Since 1992, the physicist Martina Gromoll-Bohle is responsible for production, supported by laboratory assistant Marie-Theres Holtappels.

Please contact Tom Milner for additional information, Tel: +49.2821.892-0, 
Fax: +49.2821.892-2200, E-Mail: spectro.info@ametek.com