Armen Aghajani

Fabrication and characterization of high-contrast mid-infrared GeTe 4 channel waveguides

We report the fabrication and characterization of high index contrast (Δn≈0.9) GeTe4 channel waveguides on ZnSe substrate for evanescent-field-based biosensing applications in the mid-IR spectral region. GeTe4 films were deposited by RF sputtering and characterized for their structure, composition, transparency, and dispersion. The lift-off technique was used to pattern the waveguide channels. Waveguiding from 2.5-3.7 and 6.4-7.5 μm was demonstrated, and mode intensity profile and estimated propagation losses are given for the 3.5 μm wavelength.

Spectroscopy of ytterbium-doped tantalum pentoxide rib waveguides on silicon

The design, fabrication and spectroscopic characterization of ytterbium-doped Ta2O5 rib waveguide are described. The waveguides are fabricated on silicon substrates and operate in a single mode at wavelengths above 970 nm. The peak absorption cross-section was measured to be 2.75 × 10−20 cm2 at 975 nm. The emission spectrum was found to have a broad fluorescence spanning from 990 nm to 1090 nm with the fluorescence emission peak occurring at a wavelength of 976 nm. The excited-state life time was measured to be approximately 260 µs.

Nonlinear optical properties of ytterbium-doped tantalum pentoxide rib waveguides on silicon at telecom wavelengths

We report the linear and nonlinear characterization of low loss Yb:Ta₂O₅ rib waveguides fabricated by using CMOS compatible processes on a SOI substrate. We report a nonlinear refractive index of 6.65×10^-18 m²/W measured at telecom wavelengths.

Spatially controlled doping of silver in chalcogenide glass by thermal, photo and electron beam effects

For the first time, silver doping of bulk Gallium-Lanthanum-Sulphide (GLS) and Gallium-Lanthanum-Sulphur-Selenide (GLSSe) glass is demonstrated, presenting potential for a huge array of optoelectronic applications. Previously, silver doping of chalcogenide glasses were mostly based upon toxic, arsenic containing thin films [1-3]. GLS and GLSSe, however, offer a toxic free alternative, made by a safer and more economic technique, with infrared and nonlinear optic capacity [4].

Structural modification of Ga-La-S glass for a new family of chalcogenides

In this work, the effect of adding Se, Te, In, Cs, Y to gallium lanthanum sulphide glass was studied. Structural modifications to the glassy network were achieved by substitution of sulphur, gallium or lanthanum using a melt-quench method in an inert atmosphere. Optical, thermal and mechanical characterisation of the samples revealed tailorable features according to the nature and the amount of glass modifier. In particular, the addition of selenium and tellurium resulted in an extended transmission in the infrared up to 12 μm. Furthermore, for small amounts of selenium, the position of the bandgap did not change significantly, maintaining visible transmission. The addition of indium led to the formation of glasses with longer transmission in the infrared and a cut-off edge around 600nm in the UV-visible range. Over-all, the addition of these modifiers resulted in stronger materials with improved thermal stability and similar mechanical properties to original Ga-La-S glass. The outcome of this work aims to bring a new family of chalcogenide glasses for applications in the infrared and visible range.

Spectroscopy of high index contrast Yb:Ta2O5 waveguides for lasing applications

Ytterbium-doped waveguides are required for compact integrated lasers and Yb-doped Ta2O5 is a promising candidate material. The design, fabrication and spectroscopic characterisation of Yb:Ta2O5 rib waveguides are described. The peak absorption cross-section was measured to be 2.75 x 10-20 cm2 at 975 nm. The emission spectrum was found to have a fluorescence emission peak at a wavelength of 976 nm with a peak cross-section of 2.9 x 10-20 cm2 and a second broad fluorescence band spanning from 990 nm to 1090 nm. The excited-state life time was measured to be 260 µs.

Ytterbium-Doped Tantalum Pentoxide Waveguides: Spectroscopy for Compact Waveguide Lasers

Ytterbium-doped materials are common gain media in high-performance laser systems. In this work, the first spectroscopic investigation of ytterbium-doped tantalum pentoxide (Yb:Ta2O5) for compact waveguide laser applications is presented.