ABSTRACT
Researchers have developed a uniform grating DFB with an integrated active optical feedback waveguide (UG-AFDFB) to enhance the modulation speed of direct modulation lasers (DMLs) while reducing costs based on identical active layer designations. However, this design has difficulties in obtaining high single mode yield (SMY) and low relative intensity noise (RIN) as a result of the strong optical feedback caused by the integrated active feedback waveguide (AFW) and the random phase of the facet phase. In this paper, a partial corrugated grating DFB with an integrated active optical feedback waveguide (PG-AFDFB) is proposed to address this issue. Comparison of SMY, S21, RIN, modulation eye pattern, and frequency chirp parameters between UG-AFDFB and PG-AFDFB based on time-domain transmission line laser mode reveals that PG-AFDFB with an optimized grating couple parameter κ performs significantly better than UG-AFDFB under the same conditions. Furthermore, the performance of PG-AFDFB is not sensitive to the random phase of the rear facet phase. Even when κ ranges from 6000 /m to 12000 /m, the current in the AFW is between 0â mA and 20â mA, and the length of the AFW ranges from 50â µm to 100â µm; the SMY of PG-AFDFB remains above 80%.
ABSTRACT
Purpose: Previous studies show that intergroup contact, through common ingroup identity, has impact on intergroup processes such as reducing intergroup bias, improving intergroup relations, etc. The effect of intergroup contact on individual psychological process (through common ingroup identity), however, needs further exploration. Based on the positive effect of both intergroup contact and ingroup identification on mental health and well-being, this article proposes and tests a new model of individual loneliness reduction through intergroup contact by promoting common ingroup identity. Methods: A total of 263 majority ethnic members and 275 minority ethnic members from China participated in the survey. Intergroup contact, common ingroup identity and loneliness were measured at three time-points (T1-T3) over an 8-month period. Longitudinal mediation analysis and parallel process Latent Growth Curve Model for mediation are used for the examination of the indirect effect of common ingroup identity. Results: Longitudinal mediation analysis showed that intergroup contact quality at T1 positively predicted common ingroup identity at T2, and common ingroup identity at T2 alleviated loneliness at T3. Intergroup contact quality at T1 was indirectly linked to loneliness at T3 via common ingroup identity at T2. The parallel process latent growth curve model for mediation confirmed the robustness of the indirect effect of common ingroup identity. In addition, the growth rate of the quality of intergroup contact increased the growth rate of common ingroup identity, but reduced the growth rate of loneliness. Conclusion: The current study revealed the protectiveness of intergroup contact and common ingroup identity on loneliness, viz., intergroup contact reduces individual loneliness by promoting common ingroup identity, the implication being that intergroup contact and common ingroup identity should be taken into account in intervening process of loneliness prevention so that an individual's physical and mental health could be better safeguarded.
ABSTRACT
A multi-period-delayed feedback (MPDF) photonic circuit constructed by a Sagnac ring and two coupled rings was designed. By coupling a distributed feedback (DFB) laser diode (LD) with the MPDF, a narrow linewidth semiconductor laser was demonstrated. The linewidth of the DFB-LD with MPDF was narrowed to be around 2 kHz, which is reduced by three orders of magnitude, and the linewidth reduction capability could be maintained when the wavelength of the DFB-LD was tuned in a range wider than 3 nm. The laser frequency stability can also be improved using the proposed technique, and the frequency fluctuation was reduced for nearly 8 times in comparison with the DFB-LD.
ABSTRACT
Highly selective divergent coupling reactions of benzocyclobutenones and indoles, in which the chemoselectivity is controlled by catalysts, are reported herein. The substrates undergo C2(indole)-C8(benzocyclobutenone) coupling to produce benzylated indoles and benzo[b]carbazoles in the Ni- and Ru-catalyzed reactions. A completely different selectivity pattern C2(indole)-C2(benzocyclobutenone) coupling to form arylated indoles is observed in the Rh-catalyzed reaction. Preliminary mechanistic studies suggest C-H and C-C activations in the reaction pathway. Synthetic utility of this protocol is demonstrated by the selective synthesis of three different types of carbazoles from the representative products.
