Sandra Helena Messaddeq

Study of photoinduced birefringence vs As content in thin GeAsS films

Thin films of GeAsS glass are prepared by e-beam evaporation technique. Photoinduced birefringence (PIB) is studied as function of the As content with concentrations ranging from 10% to 40%. Raman spectroscopy is used as additional tool to explain the corresponding changes undergone by the material system. The breakdown of homopolar bonds is suggested as a possible mechanism of photo induced structural changes leading to the creation of the PIB.

Self-organized periodic structures on Ge-S based chalcogenide glass induced by femtosecond laser irradiation

Self-organized periodic structures have been observed on the surface of the ablation craters of Ge-S based chalcogenide glass produced after irradiation by a focused beam of a femtosecond Ti:sapphire laser (1 kHz, 34 fs, 806 nm). Scanning electron microscopy and atomic force microscopy images of irradiated spots show a periodic structure of ripples with a spatial period of 720 nm (close to the wavelength of fs laser pulses) and an alignment parallel to the electric field of light. With an increasing number of pulses, from 5 to 50 pulses, a characteristic evolution of ripples was observed from a random structure to a series of generally aligned peaks-and-valleys self-organized periodic structures. Additionally, at the center of the ablated spot, micro-domains appear where the ripples are still regular but are assembled in a more complex fashion. The experimental observations are interpreted in terms of strong temperature gradients combined with interference of the incident laser irradiation and a scattered surface electromagnetic wave.

Study of the photosensitivity of GeS binary glasses to 800nm femtosecond pulses

We present the first study of the photosensitivity of GeS binary glasses in response to irradiation to femtosecond pulses at 800 nm. A maximum positive refractive index change of 3.5x10(-3) is demonstrated with the possibility to control the waveguide diameter from ~8 to ~50 µm by adjusting the input pulse energy. It is also demonstrated that under different exposure conditions, a maximum negative index change of -7.5x10(-3) can be reached. The present results clearly illustrate the potential of this family of glasses for the fabrication of mid-infrared waveguides.

Femtosecond laser direct inscription of mid-IR transmitting waveguides in BGG glasses

A detailed investigation of the photo-inscription of waveguides in barium gallo-germanate (BGG, BaO, GeO2, Ga2O3) glass is presented. Upon irradiation of BGG glass samples of different contents of germanium dioxide with a femtosecond laser pulse train, positive refractive index changes are produced over a wide range of exposure conditions. Waveguides with a controllable diameter ranging from 4 to 35 µm and a maximum index change up to 10−2 were inscribed. A glass sample with custom molecular composition was purified to remove hydroxyl ions and reduce the strong absorption band near 3 µm. A careful tailoring of the writing conditions allowed for the inscription of low-loss waveguides supporting only two transverse modes at the wavelength of 2.78 µm. An upper bound for the propagation losses of 0.5 ± 0.1 dB/cm was determined, showing the great potential of the BGG glass family for the fabrication of core waveguides operating in the 2-4 µm spectral range. Our results actually open a pathway towards the integration of mid-IR photonic devices based on the BGG glass family.

Role of iodine in the solubility of Tm 3+ ions in As 2 S 3 glasses

The effect of iodine (I2) on the photoluminescence properties of Tm3+ ions in the As2S3 matrix was investigated. Results showed three strong emission bands at 1.22 µm (3H5→3H6), 1.46 µm (3H4→3F4) and 1.82 µm (3F4→3H6) under the excitation wavelength of 800 nm, indicating that I2 enables the solubility of Tm3+ ions in As2S3 glasses. The concentration ratio of I2 and Tm3+ were optimized and it revealed that the increasing of the concentration of I2 of 4 times in the glass increases the solubility of Tm ions three times. The effects of the I2 on the fundamental glass properties, including optical, thermal and structural characteristics, were explored as well.

Toward the formation of crossed laser-induced periodic surface structures

The formation of a new type of laser-induced periodic surface structures using a femtosecond pulsed laser is studied on the basis of the Sipe-Drude theory solved with a FDTD scheme. Our numerical results indicate the possibility of coexisting structures parallel and perpendicular to the polarization of the incident light for low reduced collision frequency (

As 4 S 4 role on the photoinduced birefringence of silver-doped chalcogenide thin films

\gamma/\omega \lesssim 1/4

Constructive feedback for the growth of laser‐induced periodic surface structures

, where

Microstructure formation in chalcogenide thin films assisted by thermal dewetting

\omega

GLASSY MATERIALS AND LIGHT: PART 2

is the laser frequency). Moreover, these structures have a periodicity of