Electrothermal poling of soft glasses (soda lime and borosilicate glass) at relatively high currents led to the creation of a second-order optical nonlinearity. The second-harmonic generation efficiency decays in time, and the decay rate can be accelerated by exposure to intense infrared radiation.

The etching rate of silica glass in 40% hydrofluoric acid under the influence of electric fields is studied with the help of an interferometric technique. A linear dependence of etching rate with field strength was found, with a ϳ2.5% etching rate change for an applied field of 20 MV͞m. The experimental results are compared with those of a simple model that attributes this dependence to partial orientation of the HF molecules in the electric field. The measured dependence is sufficiently significant to account for the selective etching observed in frequency doubling glasses and fibers.[S0031-9007 (97)02547-7] PACS numbers: 81.65.CfEtching of silica glass ͑SiO 2 ͒ in hydrofluoric acid is an important step in the processing of microelectronic components, and this motivated studies on etching mechanisms [1] and on the role played by dopants [2] in the glass matrix. Etching in the presence of an electric field has also been investigated, and contradictory results exist in the literature. While the field created by a pn junction was observed to be capable of stopping the etching of a film of silica [3], recent results were reported where fringing fields of intensities as high as 10 MV͞m were applied to silica samples and the etching rate in a solution of HF was found to be unaffected [4]. The effect of an electric field on the etching rate of silica is of interest from a fundamental point of view and also with a view to technological applications. It has been shown that it is possible to pole by optical [5] or by electrothermal means [6] both bulk silica samples and optical fibers, creating a permanent electric field in the glass that gives rise to a strong optical nonlinearity capable of frequency doubling light. Etching is a powerful tool to study the physics behind poling, and has been used to reveal the distribution of the electric field in glass fibers [7] and in bulk glasses [8][9][10]. In order to extract further information from etching experiments it is necessary to learn what causes the unequal etching rates observed in poled glasses and fibers. In pure SiO 2 systems (such as found in poled bulk samples or in a frequency doubling fiber cladding) unequal etching can have two possible origins: (1) The etching rate may be influenced by embedded charges causing structural or chemical changes in the glass material and (2) a strong electric field alone could alter the etching velocity. In this paper an etching experiment of SiO 2 in HF is described where only an electric field can be responsible for an alteration of the etching rate. The dependence of etching rate with field strength was measured. The experimental results are compared with those of a simple model that attributes the alteration to partial orientation of the HF molecules in the electric field.An interferometric optical method was used to determine in real time the thickness of glass etched that avoided low precision mechanical measurements and the necessity to interrupt the etching process [10]. The SiO 2 samples were fixed approximately horizontall...

Glass is the most important material in optics, with uses in optical fibers, lenses, mirror substrates, and prisms. The silicate family, the prime material in this article, is well-suited for passive optical functions such as light guidance in a fiber. Because of its many desirable properties, one is tempted to use glass in active functions as well—such as in amplification and modulation of light. As early as the beginning of the 1960s, glasses doped with rare-earth ions were used as gain media for lasers. Nd:glass lasers and Erdoped fiber amplifiers are two examples of the success of the use of doped glass to perform an active optical function. The modulation and switching of light proved to be a more difficult task to perform with glass systems. Glass has very low optical nonlinearity, and the application of an electric field does little to the optical wave traveling in the material.In 1991 Myers, Mukherjee, and Brueck submitted a polymer film on a silica substrate to a poling process, which consists of the application of high voltages at a temperature of ~300°C. After cooling to room temperature with the voltage still applied, the poled sample was illuminated with a strong infrared (ir) laser beam. As expected they found that material frequency-doubled the incoming radiation and some green light could be measured at the output. When a test was carried out to discard any contribution from the substrate to the frequency-doubled light, they discovered that it was the silica glass that was generating the green light and that they had induced a strong optical nonlinearity in silica by thermal poling. Since then poling of glasses in the context of nonlinear optics has been the subject of many publications, including the report that ultraviolet (uv) radiation can advantageously replace thermal excitation.

This paper describes thermal poling of a silica based channel waveguide Mach-Zehnder interferometer, and direct measurent of the dc-Kerr and induced electro-optic coefficients. A /(3) of 5.2 (+/-0.4) x 10-22 (m/V)2 was measured for the un-poled waveguide, and r-coefficient of approximately 0.07 pm/V was induced by poling. /(3) increased by a factor of 1.9 after poling. It is shown that the dc-Kerr effect plays an important role in the poled device.

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