Rosin with bromophenol blue â dye as holographic material J. Ibarra-Torres a,b, * , A. Olivares-P erez a,b , T.J. Ibarra a,b , D. Luna-Moreno a,c a Instituto Nacional de Astrof õsica Optica y Electr onica, A.P. 51 y 216, C.P. 72000, Puebla, Pue. Mexico b Department CUCEI, Posgrado Ingenieria Civil, U. De G., Mexico c Centro de Investigaciones en Optica, Le on, Gto. Mexico Received 8 May 2000; received in revised form 26 July 2000; accepted 27 November 2000 Abstract Bromophenol blue â BPB) dyed with the rosin and isopropyl alcohol produces a ®lm with a uniform yellow ap- pearance, which can be deposited on glass plates by simple technique. This mixture shows good photosensitivity in the blue light k 457 nm line) employing argon-ion laser and presents high resolution for holographic application. Consequently, it is possible to obtain holographic elements, e.g., gratings. Ó 2001 Published by Elsevier Science B.V. PACS: 42.70; Ln Keywords: Holographic recording materials; Diraction grating 1. Introduction The bromophenol blue â BPB) tint is com- monly used as chemical indicator sensing the pH from some elements or potential acid dissociation constant pk a [1]. Its application as sensor is usual in the chemical, biomedical, environmental and espectrophotometric ®elds [2±5]. The molecular structure of BPB has elongated hexagonal prisms from acetic acid+acetone, and its condensed formula is C 19 H 10 Br 4 O 5 S [1] as is shown in Fig. 1a). In this work, we use as primary element of base the rosin, also known as colophony, given its good capacity to mix with several solvent agents. The rosin is a yellow resin and abietic anhy- dride, which is obtained from pinus palustris and other species of pinus pinaceae residues after distilling o the volatile oil from the oleoresin. Rosin is chie¯y composed of 90% resin acids that are isometric with abietic acid C 20 H 30 O 2 ) and 10% neutral matter composed of dihydroabietic acid C 20 H 32 O 2 ) and dehydroabietic acid C 20 H 28 O 2 ) [6]. Also readily fusible when heated, it has a density of 1.07±1.09 insoluble in water, freely soluble in alcohol. The mixture of the rosin and the dye bromophenol is possible by its dis- solution in isopropyl alcohol. The yellow appearance is given by the alcohol pH showed by the dye. The possible reaction between the rosin, the alcohol and the dye is described in the hy- pothesis Section 5. Other dye components are used to make optical holographic elements, e.g., crystal violet doped with photoresist shipley 1350 J, rosin resin doped with crystal violet, and methylene blue doped with Optical Materials 16 2001) 389±396 www.elsevier.nl/locate/optmat * Corresponding author. Fax: +52-2-247-29-40. E-mail address: jibarra@inaoep.mx J. Ibarra-Torres). 0925-3467/01/$ - see front matter Ó 2001 Published by Elsevier Science B.V. PII:S0925-346700)00100-2