Light structured deposition (2): Material optical functionality J.M. González-Leal a, * , A.J. Gámez a , J.A. Angel a , J. Valverde b a Department of Condensed Matter Physics, Faculty of Sciences, University of Cadiz, 11.510 Puerto Real (Cadiz), Andalusia, Spain b Department of Civil and Environmental Engineering, University of Berkeley, San Francisco, CA, USA article info Article history: Available online 22 July 2009 PACS: 81.05.Gc 81.15.Fg 42.15.Eq Keywords: Amorphous semiconductors Laser deposition abstract Aspherical refractive optical elements have been fabricated by an original light-assisted approach for deposition of semiconducting alloys. The fabrication of axicons by this method is reported for the case of an As–S binary glass alloy. The influence of both light intensity and exposure time on the deposit thick- ness profile is also presented. Ó 2009 Elsevier B.V. All rights reserved. 1. Introduction The study and the fabrication of novel aspherical optical ele- ments, both with refractive or/and diffractive functionality, is becoming an emerging area because of their advantages concern- ing the reduction of both weight and number of elements in optical systems, and their unique optical performances. In particular, it is noticeable the significant advance in the field of the axicons in the previous recent years, to exploit not only their functionalities con- cerning the extended focal length, but also their non-diffracting characteristics in optical tweezers, as well as test-boards for stud- ies of superluminar effects and both angular and orbital photon momenta [1]. Axicon lenses are well-known optical structures characterized by focusing a point source along the optical axis [2]. A conical sur- face, for instance, shows this property, and axicons based on it are called linear axicons, which are characterized by performing a practical laser beam shaping that holds the lateral resolution con- stant along the optical axis, while the light intensity varies with the distance to the axicon. Other thickness profiles as the correspond- ing to the so-called logarithmic axicons have been shown to keep both the lateral resolution and intensity constant along the optical axis, which results of interest for applications as laser drilling or la- ser marking [3]. On the other hand, the non-diffracting characteris- tics of the optical functions performed by the axicons, which are based on zeroth order Bessel functions of the first kind, are also rapidly supporting many applications in fields confocal imaging and optical trapping [3–6]. Fabrication of refractive axicons is typically carried out by tradi- tional milling and polishing techniques, while lithographic tech- niques imported from microelectronic technology [6] are mostly used for the fabrication of diffractive axicons. However, these tech- niques are far to be optimized for the fabrication of arbitrary com- plex optical structures, and new methods are emerging to overcome such a limitation [7]. In this frame, the fabrication of iso- tropic dielectric deposits with thickness profiles performing axi- con-type optical functions has been recently shown by the authors [8,9] to be realized by an original continuous-wave (cw) la- ser-assisted deposition method based on the effusion phenomenon, from a binary As–S chalcogenide semiconducting alloy. The aim of this paper is to show the different influence of laser power and exposure time in the fabrication process of axicons by this partic- ular method, from the measurement of the sample thickness pro- files with a stylus-based profilometer, as well as the monitoring of the light-intensity spatial distribution along the optical axis. 2. Experimental Samples reported here have been obtained using a cw Nd:YVO 4 laser source emitting laser radiation at 532 nm (Coherent, model Verdi 6 V), and As 20 S 80 glass alloy as starting material. This chalco- genide alloy was originally synthesized in bulk form, from their 5N-purity constituents, by conventional melt-quenching in air. Target materials were made in tablet form, 13 mm in diameter and about 1 mm in thickness, from this bulk alloy. Tablets were synthesized from the glass powder by pressing 125 mg of the start- ing material at 10 ton for 5 min, with the help of a pneumatic press. Depositions were typically performed onto transparent crys- talline (0 0 0 1) quartz substrates in 10 5 Torr vacuum by using a 0022-3093/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2009.04.058 * Corresponding author. E-mail address: juanmaria.gonzalez@uca.es (J.M. González-Leal). Journal of Non-Crystalline Solids 355 (2009) 1966–1968 Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/locate/jnoncrysol