Elsevier

Optical Materials

Volume 32, Issue 10, August 2010, Pages 1352-1355
Optical Materials

Field-assisted solid state doping of glasses for optical materials

https://doi.org/10.1016/j.optmat.2010.04.012Get rights and content

Abstract

Field-assisted solid-state ion-exchange (FASSIE) allows the doping of surface glass layers with multivalent ions which could not diffuse into the glass matrix by the usual thermal ion-exchange process in molten salt baths. This paper presents preliminary spectroscopic investigation of the diffusion of chromium in silicate glasses, with the aim at improving the procedures for the production of Cr-doped optical waveguides. Metallic chromium films deposited onto the glass substrates by the rf-sputtering technique were used as metal ions source. The environment of diffused chromium ions into the glass matrix was investigated by means of micro-Raman spectroscopy.

Introduction

Doping of the glass surface by ion diffusion is a technique largely employed in the production of passive and active waveguiding systems [1], [2], [3]. Up to now, most part of the work has been done with monovalent ions, like Ag+ and K+, which are introduced in the glass by means of the ion-exchange process with the immersion of the substrates into molten salt baths. Field-assisted solid-state ion-exchange (FASSIE) has been also exploited for the doping of glasses with Ag+ or Cu+ [4], [5], [6], [7], [8]. In this approach the diffusion of dopant ions – supplied by a film deposited onto the glass surface – is driven by the application of an external electric field: the glass slides are sandwiched between two metallic plates working as electrodes. The diffusion can be favoured by heating the samples during the electric field application. Metallic ions are then formed at the film-glass interface, that can diffuse into the glass under the external electric field. Multivalent ions are suitable for the production of active waveguiding devices for telecommunication and laser systems, but the opportunity of using them as dopants by the traditional ion-exchange process is limited mainly by the low mobility of these ion species in the glass network. In this framework, FASSIE is a quite promising technique for the production of glass waveguides containing either bivalent or trivalent ions. So far, preliminary work has demonstrated that the diffusion of gold, cobalt and erbium ions into the glass can be promoted by FASSIE [9], [10], [11], [12]. Moreover, pure silica was also doped with silver ions by FASSIE, where the diffusion of metallic ions was activated by the defects of the network [13].

In this paper, some preliminary results of a spectroscopic investigation of the diffusion of chromium in soda-lime glass (SLG) and BK7 glass substrates are presented. Besides the spectroscopic properties of Cr3+ in oxides, Cr4+ doped materials have been studied as both laser gain materials for the near IR (1.3–1.5 μm) [14], [15] and as saturable absorbers used for passive Q-switching of IR lasers in the 1.0–1.1 μm range [16], [17]. To our knowledge, no data on the diffusion of chromium in glass are currently available, and the only results on chromium-containing glass were obtained on bulk samples synthesized from melts or by means of high temperature procedures [18], [19]. Hereafter, the environment of chromium in the glass network was analyzed by micro-Raman spectroscopy.

Section snippets

Experimental

Chromium films, 20 nm thick, were deposited onto two kind of silicate glasses, 1 mm × 25 mm × 75 mm soda-lime glass (SLG) slides (atomic % composition: 59.6 O, 23.9 Si, 10.1 Na, 2.6 Mg, 2.4 Ca, 0.7 Mg, 0.5 K, 0.2 S + Ti + other elements in traces), and 1 mm × 25 mm × 70 mm borosilicate glass (BK7) slides (atomic % composition: 60.2 O, 22.4 Si, 11.0 B, 3.8 Na, 1.8 K, 0.8 Ba) in a 13.56 MHz magnetron sputtering apparatus in Ar atmosphere, at a pressure of 50 × 10−2 Pa. On the back side of the slides we deposited 150 nm of a

Results and discussion

Secondary ion mass spectrometry measurements (not reported) showed the diffusion of chromium inside the glasses, up to about 200–300 nm of depth below the surface, depending on the experimental conditions and on the glass type.

The intensity of the current flowing across the samples during the FASSIE treatment was measured during the whole process. We observed that only after few minutes from the electric field application the current intensity was detectable; moreover, its value was relatively

Conclusions

In this paper, the first results are presented concerning the doping of silicate glass with chromium by means of FASSIE procedure. As evidenced by micro-Raman analyses, in SLG the chromium forms α-Cr2O3 structures under the surface affected by a tensile stress of about 29 GPa. In BK7, the same phase is present in the glass network without any detectable stress. Moreover, the Raman spectra pointed out the presence of interdiffusion structures in a BK7 sample heated without any external applied

References (27)

  • F. Gonella et al.
  • J. Grelin et al.

    Mater. Sci. Eng. B

    (2008)
  • D. Kapila et al.

    Chem. Eng. Sci.

    (1995)
  • C. Thévenin-Annequin et al.

    Solid State Ionics

    (1995)
  • F. Gonella et al.

    Mater. Sci. Eng. C

    (2006)
  • F. Gonella et al.

    Solid State Ionics

    (2006)
  • E. Cattaruzza et al.

    Mater. Sci. Eng. B

    (2008)
  • E. Cattaruzza et al.

    J. Non-Cryst. Solids

    (2009)
  • M.A. Scott et al.

    J. Cryst. Growth

    (1998)
  • E. Munin et al.

    J. Phys. Chem. Solids

    (1997)
  • M.A.U. Martines et al.

    J. Lumin.

    (2008)
  • N. Umesaki et al.

    J. Non-Cryst. Solids

    (1996)
  • B. Boizot et al.

    J. Non-Cryst. Solids

    (2003)
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