Influence of pseudorandom bit format on the direct modulation performance of semiconductor lasers

This paper investigates the direct gigabit modulation characteristics of semiconductor lasers using the return to zero (RZ) and non-return to zero (NRZ) formats. The modulation characteristics include the frequency chirp, eye diagram, and turn-on jitter (TOJ). The differences in the relative contributions of the intrinsic noise of the laser and the pseudorandom bit-pattern effect to the modulation characteristics are presented. We introduce an approximate estimation to the transient properties that control the digital modulation performance, namely, the modulation bit rate and the minimum (setting) bit rate required to yield a modulated laser signal free from the bit pattern effect. The results showed that the frequency chirp increases with the increase of the modulation current under both RZ and NRZ formats, and decreases remarkably with the increase of the bias current. The chirp is higher under the RZ modulation format than under the NRZ format. When the modulation bit rate is higher than the setting bit rate of the relaxation oscillation, the laser exhibits enhanced TOJ and the eye diagram is partially closed. TOJ decreases with the increase of the bias and/or modulation current for both formats of modulation.     

微流控芯片非接触电导法测定药品中的精氨酸布洛芬含量

建立了微流控芯片非接触电导检测快速测定精氨酸布洛芬含量的方法。考察了缓冲液种类和浓度、添加剂、分离电压以及进样时间等因素对分离检测的影响。优化条件为:20 mmol/L Tris-20 mmol/L H3BO3(p H 8.6)为缓冲溶液、不加添加剂、分离电压2.0 k V、进样时间10.0 s,在45.0 s内可实现精氨酸布洛芬的快速分离测定。结果表明,布洛芬和精氨酸在80.0~1.00×103mg/L范围内线性关系良好,相关系数(r)分别为0.998和0.997,检出限(S/N=3)为60 mg/L,相对标准偏差分别为1.9%和1.8%,加标回收率分别为97.9%~103%和97.3%~102%。该方法快速、简便,为精氨酸布洛芬非甾体抗炎药物的分析和质量控制提供了一种新方法。     

Determination of optical constants and nonlinear optical coefficients of Violet 1-doped polyvinyl alcohol thin film

The optical properties of Violet 1-doped polyvinyl alcohol (PVA) have been investigated using Wemble and Didomenico (WD) method. The optical constants such as refractive index n, the dispersion energy E _d, the oscillation energy E ₀, the lattice dielectric constant \(\varepsilon _{\infty } \), light frequency dielectric constant ε ₀ and the ratio of carrier concentration to the effective mass N/m* have been determined using reflection spectra in the wavelength range 300–900 nm. The single- beam Z-scan technique was used to determine the nonlinear optical properties of Violet 1:polyvinylalcohol (PVA) thin film. The experiments were performed using continuous wave (cw) laser with a wavelength of 635 nm. The calculated nonlinear refractive index of the film, n ₂ = ?2.79×10^?7 cm²/W and nonlinear absorption coefficient, β = 6.31×10^?3 cm /W. Optical limiting characteristics of the dye-doped polymer film was studied. The result reveals that Violet 1 can be a promising material for optical limiting applications.