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In this paper, we study a kind of near optimal control problem which is described by linear quadratic doubly stochastic differential equations with time delay. We consider the near optimality for the linear delayed doubly stochastic system with convex control domain. We discuss the case that all the time delay variables are different. We give the maximum principle of near optimal control for this kind of time delay system. The necessary condition for the control to be near optimal control is deduced by Ekeland's variational principle and some estimates on the state and the adjoint processes corresponding to the system. [ABSTRACT FROM AUTHOR]

The microhardness of chalcogenide glasses (ChGs) of the Sn–Sb–Se (SSS) ternary system was investigated, and the correlation of microhardness with the mean coordination number of the SSS ChGs was determined. To prepare infrared‐transparent SSS glass‐ceramics (GCs), two SSS ChGs (A, Sn6.23Sb14.11Se79.66; B, Sn9.8Sb17.22Se72.98; by molar composition) were selected and thermally treated at 433 and 448 K, respectively. The improved microhardness (with values that increased by 11.5% and 7.3% for SSS ChG A and B, respectively) of the resulting SSS GCs is attributed to the formation of Sb2Se3 nanocrystals. [ABSTRACT FROM AUTHOR]

Ge28Sb12Se60 waveguides and microresonators were fabricated by thermal evaporation and dry etching technology. The low loss waveguides and high-index-contrast Ge28Sb12Se60 microring resonators were developed and demonstrated using the optimal parameters of CF4/CHF3 etching recipe. An intrinsic quality factor (Q-factor) of 2.3 × 105 with propagation loss of 2.4 dB/cm at 1550 nm was obtained in this microring resonator with 800 × 400 nm cross-sectional dimension. Critically coupled resonator showed extinction ratio of >30 dB. Nonlinear refractive index (n 2) of 5.12 × 10−18 m2/W for Ge28Sb12Se 60 glass was measured and nonlinear coefficient (γ) of 24 W−1 m −1 asfabricated waveguide was also estimated. This paper illustrates the potential of Ge28Sb 12Se60 glass as a low loss and large nonlinearity material for integrated photonics applications. [ABSTRACT FROM AUTHOR]

A systematic investigation of the optical and structural properties of chalcogenide glasses in Ge-Sn-Se ternary system is presented. We have found a threshold behavior of optical property, namely, existence of transitional composition of the Ge-Sn-Se glasses, with progressive replacement of Se by Sn. Calculation of mean coordination number indicates that the transition-like feature of optical property is associated with the evolution of chemical ordering of the Ge-Sn-Se network. Analysis of Raman spectra of the glasses explains that the interaction between Se-Se bonds, Sn(Se1/2)4 tetrahedra, and Sn-Sn homopolar bonds is the origination of such optical phenomenon. [ABSTRACT FROM AUTHOR]

In this work, we investigated the mid-infrared (MIR) optical properties of selenide (Se-based) chalcogenide glasses (ChGs) within an As- and Ge-free system, namely the environment-friendly and low-cost tin-antimony-selenium (Sn-Sb-Se, SSS) ternary system, which has not been systematically studied to the best of our knowledge. As compared to ChGs within those conventional Se-based systems, SSS ChGs were found to exhibit extended infrared transmittance range as well as larger linear refractive index (n 0 ). Femtosecond Z-scan measurements show the presence of evident three-photon absorption from Urbach absorption of the SSS ChGs at MIR wavelength, which resonantly enhanced the nonlinear refractive behavior and resulted in large nonlinear refractive index (n 2 ).