Dependence of nonlinear refractive index of ZnSe on Be and Mg content

The values of the nonlinear refractive index n(2) and the two-photon absorption coefficient beta of ternary and quaternary ZnSe-based mixed crystals were extracted from the standard backward degenerate four wave mixing (DFWM) and nonlinear transmission measurements at 532 nm, respectively. Studied crystals were grown by the modified high-pressure Bridgman method. We found that the value of the nonlinear refractive index n(2) for Zn(0.79)Be(0.21)Se is higher than that for Zn(0.80)Mg(0.20)Se. However, the opposite behaviour was found in the case of two-photon absorption coefficient beta for these compounds. We also found that the values of the nonlinear refractive index n(2) and the two-photon absorption coefficient beta for Zn(0.83)Be(0.04)Mg(0.13)Se are about five times lower and three times higher than that for Zn(0.80)Mg(0.13)Se, respectively. In the case of ternary ZnSe-based crystals we noticed that the value of the nonlinear refractive index n2 decreases with increasing Mg or Be content. However, the value of the two-photon absorption coefficient beta increases with increasing Mg or Be content

Study of the third order nonlinear optical properties of Zn1−xMgxSe and Cd1−xMgxSe crystals

Third order nonlinear optical susceptibilities χ<3> of ternary Zn1−xMgxSe and Cd1−xMgxSe crystals have been measured using standard degenerate four-wave mixing (DFWM) method at 532 nm. The nonlinear transmission technique has been applied to check if our crystals exhibit two-photon absorption. The studied Zn1−xMgxSe and Cd1−xMgxSe solid solutions were grown from the melt by the modified high-pressure Bridgman method. For both crystals the energy gap increases with increasing Mg content. In the case of Zn1−xMgxSe, it was found that the value of third order nonlinear optical susceptibility χ<3> decreases with increasing Mg content. An explanation of this behaviour results from the dependence of optical nonlinearities on the energy band gap Eg of the studied crystals. In the case of Cd1txMgxSe with low content of Mg, no response was observed for the studied wavelength since the energy gap in such crystals is smaller than the photon energy of the used laser radiation. It was also found that the value of third order nonlinear optical susceptibility χ<3> for Cd0.70Mg0.30Se is higher than for Zn0.67Mg0.33Se. This behaviour can be understood if one take into consideration that the free carrier concentration in Cd1−xMgxSe samples is about four orders of magnitude higher than that in Zn1txMgxSe ones with comparable Mg content respectively. It is commonly known that when the electric conductivity increases, the values of nonlinear optical properties increase. From the performed measurements one can conclude that the incorporation of Mg as constituent into ZnSe and CdSe crystals leads to a change of the third order nonlinear optical susceptibilities

Ear–voice span and pauses in intra- and interlingual respeaking: An exploratory study into temporal aspects of the respeaking process

Respeaking involves producing subtitles in real time to make live television programs accessible to deaf and hard of hearing viewers. In this study we investigated how the type of material to be respoken affects temporal aspects of respeaking, such as ear–voice span and pauses. Given the similarities between respeaking and interpreting (time constraints) and between interlingual respeaking and translation (interlingual processing), we also tested whether previous interpreting and translation experience leads to a smaller delay or lesser cognitive load in respeaking, as manifested by a smaller number of pauses. We tested 22 interpreters, 23 translators, and a control group of 12 bilingual controls, who performed interlingual (English to Polish) and intralingual (Polish to Polish) respeaking of five video clips with different characteristics (speech rate, number of speakers, and scriptedness). Interlingual respeaking was found to be more challenging than the intralingual one. The temporal aspects of respeaking were affected by clip type (especially in interpreters). We found no clear interpreter or translator advantage over the bilingual controls across the respeaking tasks. However, interlingual respeaking turned out to be too difficult for many bilinguals to perform at all. To the best of our knowledge, this is the first study to examine temporal aspects of respeaking as modulated by the type of materials and previous interpreting/translation experience. The results develop our understanding of temporal aspects of respeaking and are directly applicable to respeaker training

Nonlinear optical properties of Zn1−xMgxSe and Cd1−xMgxSe crystals

Nonlinear optical properties of Zn1−xMgxSe and Cd1−xMgxSe crystals have been studied using degenerate four wave mixing (DFWM), nonlinear transmission (NLT), second harmonic generation (SHG) and third harmonic generation (THG) methods by Nd:YAG laser operating at 532 nm and 1064 nm, respectively. The studied Zn1−xMgxSe and Cd1−xMgxSe crystals were grown from the melt by the modified high-pressure Bridgman method. The quadratic nonlinear optical properties of ternary crystals were investigated by second harmonic generation (SHG) technique. We found that the highest value of the second order nonlinear optical susceptibility was obtained for Cd0.7Mg0.3Se. In the case of cubic nonlinear optical properties we used third harmonic generation (THG) and degenerate four wave mixing (DFWM) methods. We found that the values of third order nonlinear optical susceptibility for Cd1−xMgxSe crystals are higher than for Zn1−xMgxSe ones

Thermal diffusivity, effusivity and conductivity of CdMnTe mixed crystals

Cd1-xMnxTe mixed crystals belong to a class of materials called ‘‘semimagnetic semiconductor’’ or diluted magnetic semiconductor (DMS) with addition of magnetic ions like Mn2+ implemented into crystal structure. The crystals under investigation were grown from the melt by the high pressure high temperature modified Bridgman method in the range of composition 0 < x < 0.7. Thermal properties of these compounds have been investigated by means of photopyroelectric (PPE) calorimetry in both, back and front detection configuration. The values of the thermal diffusivity and effusivity were derived from experimental data. Thermal conductivity of the specimens was calculated from the simple theoretical dependencies between thermal parameters. The influence of Mn concentration on thermal properties of Cd1-xMnxTe crystals have been presented and discussed

Vocal fold vibratory patterns in tense versus lax phonation contrasts

This study explores the vocal fold contact patterns of one type of phonation contrast--the tense vs lax phonation contrasts of three Yi (Loloish) languages. These contrasts are interesting because neither phonation category is very different from modal voice, and because both phonations are largely independent of the languages' tonal contrasts. Electroglottographic (EGG) recordings were made in the field, and traditional EGG measures were derived. These showed many small but significant differences between the phonations, with tense phonation having greater contact quotients and briefer but slower changes in contact. Functional data analysis was then applied to entire EGG pulse shapes. The resulting first principal component was found to be mostly strongly related to the phonation contrasts, and correlated with almost all the traditional EGG measures. Unlike the traditional measures, however, this component also seems to capture differences in abruptness of contact. Furthermore, previously collected perceptual responses from native speakers of one of the languages correlated better with this component than with any other EGG measure or any acoustic measure. The differences between these tense and lax phonations are not large, but apparently they are consistent enough, and perceptually robust enough, to support this linguistic contrast