Unperturbed dimensions of stereoregular polymers.- Reinforcement of rubber by carbon black.- Transformations of phenolic antioxidants and the role of their products in the long-term properties of polyolefins.

Properties of polymers

We demonstrate the continuous tuning of the electronic structure of atomically thin MoS2 on flexible substrates by applying a uniaxial tensile strain. A redshift at a rate of ~70 meV per percent applied strain for direct gap transitions, and at a rate 1.6 times larger for indirect gap transitions, have been determined by absorption and photoluminescence spectroscopy. Our result, in excellent agreement with first principles calculations, demonstrates the potential of twodimensional crystals for applications in flexible electronics and optoelectronics.

Experimental demonstration of continuous electronic structure tuning via strain in atomically thin MoS2

We demonstrate the continuous tuning of the electronic structure of atomically thin MoS2 on flexible substrates by applying a uniaxial tensile strain. A redshift at a rate of ∼70 meV per percent applied strain for direct gap transitions, and at a rate 1.6 times larger for indirect gap transitions, has been determined by absorption and photoluminescence spectroscopy. Our result, in excellent agreement with first principles calculations, demonstrates the potential of two-dimensional crystals for applications in flexible electronics and optoelectronics.

Experimental Demonstration of Continuous Electronic Structure Tuning via Strain in Atomically Thin MoS2

In this report dispersion properties of dierent types of optical polymers are discussed on the base of measured refractive indices and the Cauchy‐Schott approximation. A number of dispersion curves are presented in the visible and near infrared spectral regions between 400 and 1060 nm. A comparison with some optical glasses with similar refraction is performed. The nonlinear dependence of dn=d‚ of polymer materials and test glasses on the wavelength is calculated and analyzed. Normalized dispersion curves at 550 nm and 880 nm are presented to illustrate better the dispersion of the polymers in the considered spectral regions, separately. Abbe numbers are calculated to exhibit the mean and partial dispersion.

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Dispersion Properties of Optical Polymers

Analysis of the dispersion of optical plastic materials

A He-Ne laser device has been used for refractometric measuring of a number of optical plastic (OP) specimens. We applied an ellipsometric laser system for the index of refraction initial determination. A table of the experimentally obtained refractive indices of various types of the principal and some new developmental OPs at the laser wavelength λ=632.8 nm is illustrated. The dispersion coefficients of ten American, Japanese and German OP samples were computed using a modified Cauchy's dispersive equation. A table of OP's refractive indices calculated at twenty laser wavelengths in the spectral area from 405 nm (GaN LD) to 1064 nm (YAG devices) is presented.

Laser measurements of optical plastics

In this report three types of optical polymer thin films deposited on glass substrates are investigated. Transmission
spectra of the polymer samples are obtained in the range from 400 nm to 1500 nm. A laser microrefractometer has been
used to measure the refractive indices of the examined materials at 406, 656, 910 and 1320 nm. Dispersion properties of
the polymer films are analyzed on the base of the Cauchy-Schott's and Sellmeier`s approximations. Dispersion
coefficients are calculated and dispersion charts in the visible and near infrared spectral regions are presented and
compared. Abbe numbers of mean and partial dispersion of the polymer films are obtained. Calculation of refractive
indices at many laser emission wavelengths in the considered spectral range is accomplished.

Optical properties of thin polymer films

Refractive data for more than fifteen types of American, German and Japanese optical polymers at laser emission wavelengths in the visible and near-infrared spectral regions from 406.7 nm (Krypton) to 1080 nm (Nd:YAP) is presented. We have measured the refractive indices of the examined optical plastics (OPs) at selected wavelengths from 435.8 nm to 1052 nm with an accuracy of ±0.001. Laser measurements at HeNe emission wavelength λ=632.8 nm have been also accomplished. A modified Caushy's dispersion formula for computer modelling of the refractive characteristics of OPs in the region of normal dispersion is utilized. On its basis a new OptiColor program is realized for determination of the dispersion coefficients and dispersion curves of any optical material. The obtained data for the OPs' dispersion coefficients, refractive indices at laser emission wavelengths, and dispersion charts could be useful for the 
optical designers and production technologists of laser devices.

Stefka N. Kasarova

Papers

Dispersion Properties of Optical Polymers

Analysis of the dispersion of optical plastic materials

Laser measurements of optical plastics

Optical properties of thin polymer films

Refractive data of optical plastics for laser applications