Robert Stegeman

Tellurite glasses with peak absolute Raman gain coefficients up to 30 times that of fused silica.

An experimental system has been assembled to measure the absolute values of the Raman gain spectrum for millimeter-thick glass samples. Results are reported for two new oxide glasses with Raman gain coefficients as much as 30 times larger than that of fused silica and more than twice its spectral coverage.

Resolved discrepancies between visible spontaneous Raman cross-section and direct near-infrared Raman gain measurements in TeO2-based glasses.

Disagreements on the Raman gain response of different tellurite-based glasses, measured at different wavelengths, have been recently reported in the literature. In order to resolve this controversy, a multi-wavelength Raman cross-section experiment was conducted on two different TeO2-based glass samples. The estimated Raman gain response of the material shows good agreement with the directly-measured Raman gain data at 1064 nm, after correction for the dispersion and wavelength-dependence of the Raman gain process.

Raman gain measurements in bulk glass samples

Increased interest in highly nonlinear glasses for use as Raman amplifiers has encouraged the development of an experimental apparatus to measure the material Raman gain coefficient on millimeter-thick bulk glass samples. Apparatus design considerations, details of the apparatus, and justification for the data analysis employed are provided. The apparatus is a powerful tool offering the ability to quickly screen glass samples over a wide range of compositions without the time and cost of fiberizing candidate materials into a guiding geometry to directly measure Raman gain.

Raman gain measurements and photo-induced transmission effects of germanium- and arsenic-based chalcogenide glasses

The Raman gain spectra of millimeter thick As(2)S(3) and As(24)S(38)Se(38) glasses and Ge((23 - x))Ga(x)Sb(7)S((70 - y))Se(y) with x = 0 and 5 and y = 0, 2, 5 have been measured using a direct nonlinear optics technique. The pump light originated from a picosecond Nd:YAG laser operating at 1064 nm and a tunable optical parametric generator and amplifier (OPG/OPA) was used as a source for the probe light. A peak material Raman gain coefficient of (155 +/- 11) x 10(-13) m/W has been measured for the As(24)S(38)Se(38) glass. A reversible photodarkening effect which responds to picosecond pulses is also reported. Finally, surface optical damage threshold measurements were found to be less than 9 GW/cm(2) for the reported samples, values which are comparable to some TeO(2)-based glasses with lower nonlinearities.

Influence of modifier oxides on the structural and optical properties of binary TeO2 glasses

Five different glass compositions with equal TeO2 molar concentration and various intermediate constituents were prepared to examine the influence of such intermediate species on the tellurite network. A correlation between the glasses’ structural network and optical properties is presented. Peak Raman gain coefficients, on the order of 40 times the gain of SiO2, are reported in this paper.

Soliton transients and supercontinuum generation in high-Raman-gain materials

Modification of the Raman response of a nonlinear-optical material can dramatically change the spectral and temporal evolution of ultrashort pulses, leading to new interesting and practically significant regimes of short-pulse dynamics. We show that, in fibers with a high Raman gain, solitonic spikes can arise only as transient features in the fast dynamics of ultrashort field waveforms. Enhanced Raman scattering induces a fast frequency downshift of these transients, preventing the formation of temporally and spectrally isolated solitons and giving rise to new highly efficient regimes of supercontinuum generation.

Glasses for Raman nonlinear optics

The Raman effect, by which light is frequency shifted by a vibrational mode, enters into a number of phenomena in nonlinear optics. Here, we summarize our progress in identifying glass materials with potentially useful Raman properties, methods for measuring the strength of the Raman effect and its spectral dependence, and the properties of a number of different families of glasses. Glasses with both larger peak Raman susceptibilities and larger bandwidths relative to fused silica are reported.

Measurement of Third-Order Nonlinear Susceptibility Tensor Elements in Lithium Niobate

We report on measurements of the main-axis elements of the third-order nonlinear electronic susceptibility of lithium niobate with nonlinear spectroscopy experiments.

Ultrahigh electro-optic coefficient of 170pm/V and low V π of 1V at 1.55μm in hybrid polymer/sol-gel waveguide modulators

We demonstrated the highest electro-optic (EO) coefficient with the highest poling efficiency (~100%) in actual modulator devices. This breakthrough was accomplished with contact poling of a crosslinkable EO polymer with an electrically conductive sol-gel cladding.

New glasses and their characterization for Raman gain

There are two current methods for estimating the Raman gain properties of materials - measuring the spontaneous Raman spectrum and comparing it to that of fused silica, and fabricating a fiber and measuring the gain directly. We have developed a new apparatus for measuring directly the absolute value of the Raman gain spectrum in bulk materials whose thicknesses is only a few millimeters. This apparatus will be described and has proven valuable for rapid evaluation of materials. A table of Raman gain will be given for different glass families including tellurites, post-transitional heavy metals, and mixed cation glasses.