Yb-ASE Suppression in Single-Frequency Hybrid Double Cladding Erbium–Ytterbium Co-Doped Fiber Amplifier with SMS Structure

A hybrid double cladding erbium–ytterbium co-doped fiber (EYDF) amplifier with a single-mode-multimode-single-mode (SMS) active fiber is demonstrated in this study. The hybrid gain fiber with an SMS structure is composed of two kinds of EYDFs with 6 and 12 μm core diameters. The transmission spectra of the SMS fiber structure were theoretically analyzed and the simulation results indicated that the maximum loss in the 1~1.1 μm band where the Yb-band amplified spontaneous emission (Yb-ASE) located, was much larger than that of the 1.5-μm band because of the wavelength difference. The power performance and spectra properties of the hybrid fiber amplifier were theoretically and experimentally analyzed and compared with a typical uniform fiber amplifier under the same conditions. The experimental results demonstrated that this hybrid fiber amplifier can suppress the Yb-ASE by over 12 dB and increase the slope efficiency by more than 2%, but the ASE in the 1.5-μm band increases by 2~3 dB. This work provides a possible method to enable EYDF amplifiers to suppress the Yb-ASE and overcome the pump bottleneck effect.

Theoretical assessment of Raman spectra on MXene Ti2C: from monolayer to bilayer

The structural, vibrational and Raman spectra properties of monolayer and bilayer Ti2C excited by two commonly used laser lines (532 nm and 633 nm) are investigated by first principles calculations...

Developing a multi-spectral imaging system using a RGB camera under two illuminations

This paper proposes a multi-spectral imaging system, developed using a commercial-grade camera, under two commonly used illumination. Rather than using conventional direct or diffuse light, the novelty of our method is to use a cross-polarized imaging system to eliminate glare and specular highlights. Two RGB images are captured under two different color temperature lighting conditions. An improved reflectance estimation method is developed to transform camera RGB under two illumination to spectral reflectance using a regulated model, combining the polynomial expansion of the camera signals with optimally selected feature. The method was tested using both a semi-gloss ColorChecker SG (140) and matte ColorChecker DC (240) chart. The results indicate that the proposed method significantly outperforms the traditional methods both in terms of spectra and colorimetric accuracy. This new multi-spectral imaging system is sufficiently precise to predict spectra properties and its performance within an acceptable range.

Influence of energy gap between charge-transfer and locally excited states on organic long persistence luminescence

Organic long-persistent luminescence (LPL) is an organic luminescence system that slowly releases stored exciton energy as light. Organic LPL materials have several advantages over inorganic LPL materials in terms of functionality, flexibility, transparency, and solution-processability. However, the molecular selection strategies for the organic LPL system still remain unclear. Here we report that the energy gap between the lowest localized triplet excited state and the lowest singlet charge-transfer excited state in the exciplex system significantly controls the LPL performance. Changes in the LPL duration and spectra properties are systematically investigated for three donor materials having a different energy gap. When the energy level of the lowest localized triplet excited state is much lower than that of the charge-transfer excited state, the system exhibits a short LPL duration and clear two distinct emission features originating from exciplex fluorescence and donor phosphorescence.

Nanoparticle Interactions and Molecular Relaxation in PLA/PBAT/Nanoclay Blends

Organo-modified clay nanoparticles were mixed at 1 and 5 wt% concentrations with a molten blend of 75 wt% of polylactide (PLA) and 25 wt% poly[(butylene adipate)-co-terephthalate] (PBAT). Three mixing strategies were used to control the localization of nanoclay. Small amplitude oscillatory shear (SAOS) and stress growth tests were conducted to clarify the nanoclay interactions with the blend components and its effect on the molecular relaxation behavior. SAOS and weighted relaxation spectra properties were determined before and after pre-shearing at a rate of 0.01 s−1. Molecular relaxation and its characteristics were influenced by PLA degradation, PBAT droplet coalescence, and nanoclay localization.

SYNTHESIS OF 1,2 DISUBSTITUTED BENZO 1,3-DIAZOLE DERIVATIVES AND EVALUATION OF THEIR INVITRO ANTI-TUBERCULAR ACTIVITIES

The present research work was aimed to synthesize some Mannich bases of benzo1,3-diazole dervivatives and was investigated for their biological activities. The newly synthesized compounds have been characterized by their analytical and spectral (IR, 1HNMR, Mass spectra) properties. All the compounds have been screened for their antitubercular activities by standard methods. Antitubercular study revealed that Both BZ2 and BZ5 have promising activity. Keywords: Benzo1,3-diazole, o-phenylenediamine, urea, benzamide, Hydroxylamine, Antitubercular activity.