Chalcogenide Glasses and their Photosensitivity ... - OSA Publishing

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E-mail, ncarlie@clemson.edu jdm047@clemson.edu, gguery@clemson.edu lpetit@clemson.edu, ... Department: College of Optics and Photonics CREOL/FPCE,. Name of organization University of Central Florida, Orlando,. Address: 4000 ...
OSA / BGPP 2010 a184_1.pdf BWD1.pdf

Chalcogenide Glasses and their Photosensitivity: Engineered Materials for Device Applications J. David Musgraves, Nathan Carlie, Guillaume Guery, Peter Wachtel, Laeticia Petit, Kathleen Richardson* Department: School of Materials Science and Engineering Name of organization: Clemson University Address: 161 Sirrine Hall, Clemson SC 29634, USA E-mail, [email protected] [email protected], [email protected] [email protected], [email protected] [email protected]

Juejun Hu, Anu Agarwal, Lionel Kimerling Department: Micro-photonics Center, Name of organization: Massachusetts Institute of Technology, Address: 77 Mass. Ave., Cambridge, MA 02139, USA E-mail: [email protected], [email protected], [email protected]

Troy Anderson, Jiyeon Choi, Martin Richardson Department: College of Optics and Photonics CREOL/FPCE, Name of organization University of Central Florida, Orlando, Address: 4000 Central Florida Boulevard, FL 32816, USA E-mail: [email protected], [email protected] , [email protected] *Corresponding author

Abstract: Chalcogenide glasses are widely used in device applications which capitalize on their unique linear and nonlinear optical properties, and infrared transparency. The role of the glass’ photosensitivity in device fabrication and eventual use, is discussed. ©2010 Optical Society of America OCIS codes: 160.0160, 160.2750, 160.4670, 230.0230, 230.7370, 230.5750, 300.1030

1. Introduction Chalcogenide glasses (ChGs) have been studied extensively for next-generation optical fiber applications, including Raman gain [1], super-continuum generation [2], and for use as micro-structured fiber [3]. ChGs possess excellent infrared transparency, large linear and nonlinear refractive indices, low phonon energies, and their properties are tunable through compositional tailoring. The high transparency of these glasses in the infrared also leads to possible applications in optical molecular sensing, as most organic substances and functional groups have signature fingerprint absorptions in this spectral region. Recently these glasses have been evaluated as platform materials for planar “on-chip” microfluidic sensors amenable to functionalization with chem- or bio-specific polymeric coatings [4, 5, 6 and references therein]. Combined with ease of processing, these attributes make ChGs good candidates for near-, mid- and long-wave IR applications as compared to oxide glasses and single crystals. For the purposes of device design, it is often necessary to tailor certain optical or thermal properties, as well as their photo-sensitivity, or photo-induced property changes of the glass when used for planar or fiber waveguide fabrication. 2. Photo-sensitive Response in Chalcogenide Glasses The intrinsic photosensitivity of chalcogenide glasses has been exploited in a range of applications and can be traced back to both the molecular structure of the glass, and its resulting bandgap as compared to the wavelength of use. The photo-induced changes in the linear and nonlinear optical properties of optical glasses have been widely studied [7], and yet are still not completely understood. In order to better characterize the effects of slight compositional changes on the photosensitivity of these glasses for this study, bulk glasses and thin films of a wide variety of stoichiometry have been evaluated. Specific to this talk, films have been prepared which utilize a substitution of one metal species (Ge or Sb) for another (As). Irradiation of the glassy films was conducted using a extended cavity Ti:Sapphire oscillator at 795 nm center wavelength, the details of which are described elsewhere [8]. Figure 1 presents the photo-induced refractive index change and local photo-expansion of the films, highlighting the pronounced effect of the glass constituent’s electronic behavior, on the resulting ChGs photo-sensitivity.

OSA / BGPP 2010

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a184_1.pdf BWD1.pdf

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(a) (b) Fig. 1: Photo-expansion (a) and photo-induced refractive index change (b) as a function of integrated laser dose at λ = 795 nm, for As42S58, As36Ge6S58, and As36Sb6S58 glass films

3. Engineering Glass Compositions for Desired Photo-Response Optimal implementation of ChGs into next–generation optical devices is predicated on a precise understanding of their photo-induced property response at the wavelength of use. This in turn necessitates a fundamentally sound interpretation of the relationship between glass structure/composition and properties. Interpretation of the results depicted in Figure 1 has been performed through the use of Raman spectroscopy, chemometric techniques, and density functional theory models. Correlation of changes in the Raman spectra of the films to physical observables such as photo-expansion (shown visually in Figure 2, below) indicates the contribution of multiple structural and electronic phenomena to the photosensitivity displayed by these materials. These techniques have been extended past the point of data interpretation and into use in engineering glass compositions with uniquely tailored optical and thermal properties. 1.5 1.0 1.4

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Fig. 2: Relative peak areas for 220, 235 and 490 cm-1 Raman spectral features for As36Ge6S58 films as a function of photo-expansion height

4. Conclusions An interdisciplinary team of researchers at Clemson University, MIT and University of Central Florida have fabricated and characterized the photo- response of a wide variety of chalcogenide glasses in both bulk and thin film form. The photo-sensitivity of candidate glasses for device applications can be dramatically affected by slight variations in glass composition. Interpretation of the structure/property relationship evidenced in these materials has been enhanced through modeling and chemometric analysis. These tools have been successfully employed to engineer glasses with precise optical and thermal properties. References [1] R. Stegeman et al, “Raman gain measurements and photo-induced transmission effects of germanium- and arsenic-based chalcogenide glasses”, Optics Express, 14 (2006) 11702-11708 [2] A.B. Seddon, “Chalcogenide glasses – A review of their preparation, properties and applications”, J. Non-Cryst. Sols. 184 (1995) 44-50 [3] F. Désévédavy et al, “Small-core chalcogenide microstructured fibers for the infrared”, Appl. Optics 47 (2008) 6014-6021 [4] L. Petit et al, “Development of novel integrated bio/chemical sensor systems using chalcogenide glass materials,” Int. J. of Nanotechnology, 6 (2008) 799-814 [5] K. Richardson et al, “Progress on the fabrication of on-chip, integrated chalcogenide glass (ChG)-based sensors,”, in press J. Nonlinear Opt. Phys. & Materials (2010) [6] J. Hu et al, “Resonant cavity enhanced photosensitivity in As2S3 chalcogenide glass at 1550 nm telecommunication wavelength,” in press, Opt. Letts. (2010) [7] H. Ebendorff-Heidepriem, “Laser writing of waveguides in photosensitive glasses”, Optical Materials, 25 (2004) 109–115 [8] T. Anderson et al, “Evaluation of the femtosecond laser photo-response of Ge23Sb7S70 films”, Optics Express, 16 (2008) 20081- 20098