Graphene Q-switched mode-locked waveguide laser operating at 1535 nm

A diode-pumped Er,Yb:glass waveguide laser, Q-switched mode-locked using a graphene saturable absorber is presented. Mode-locked pulses at a repetition rate of 6.8 GHz are achieved at an output power of 27 mW and a wavelength of 1535 nm

Towards an all-integrated MOPA configuration using Yb-doped ion-exchanged waveguides

In this paper, we present an ion-exchanged Yb-glass waveguide amplifier, seeded by an ion-exchanged Yb-glass waveguide laser demonstrating a gain as high as 10 dB. We also present multi-GHz, mode-locked ion-exchanged waveguide lasers and discuss the development of a fully integrated high-power, multi-GHz waveguide sourc

Near-infrared, mode-locked waveguide lasers with multi-GHz repetition rates

In this work, we discuss mode-locking results obtained with low-loss, ion-exchanged waveguide lasers. With Yb3+-doped phosphate glass waveguide lasers, a repetition rate of up to 15.2 GHz was achieved at a wavelength of 1047 nm with an average power of 27 mW and pulse duration of 811 fs. The gap between the waveguide and the SESAM introduced negative group velocity dispersion via the Gires Tournois Interferometer (GTI) effect which allowed the soliton mode-locking of the device. A novel quantum dot SESAM was used to mode-lock Er3+, Yb3+-doped phosphate glass waveguide lasers around 1500 nm. Picosecond pulses were achieved at a maximum repetition rate of 6.8 GHz and an average output power of 30 mW. The repetition rate was tuned by more than 1 MHz by varying the pump power

Graphene q-switched Yb: phosphate glass channel waveguide laser

Q-switched lasers can generate high-energy pulses that can have applications in medicine, material processing and defence. Waveguide lasers have several attractive features such as a low laser threshold and a high slope efficiency, provided that the propagation losses are kept low, compactness and mass-producibility. Ion-exchange is a simple and cheap technique to fabricate loss-loss waveguides in glass, with mode-locked operation being demonstrated in ion-exchanged Yb:phosphate glass lasers using a semiconductor saturable absorber mirror (SESAM). Using graphene as a saturable absorber has several key advantages over SESAMs such as a broad wavelength operating range, cost-effectiveness and ease of fabrication. Graphene has previously been used as a saturable absorber to demonstrate Q-switched mode-locking in a femtosecond-written glass waveguide laser and Q-switched operation in a carbon-irradiated Nd:YAG ceramic channel waveguide laser. In this paper we present an ion-exchanged Yb:phosphate glass waveguide laser, Q-switched using a graphene saturable absorber

Temperature-induced exciton switching in long alkyl chain based inorganic-organic hybrids

Photoluminescence and transmission is systematically explored in thin films of long-alkyl-chain-based inorganic-organic (IO) hybrids (CnH2n+1NH3)2PbI4 (n=12, 16, 18) (CnPI) and NH3C12H22NH3PbI4 (DDPI). Such IO-hybrids, which form natural multiple quantum well structures stacked up along c-axis, possess strong room-temperature exciton transitions. These hybrids exhibit reversible phase transition of two different crystal phase transitions at easily accessible device temperatures. Flipping the structural phase is clearly reflected in switching of the excitons with corresponding photoluminescence and transmission changes showing clear thermal hysteresis. The phase-dependent switching of excitons is predominantly due to reversible crumpling of the inorganic PbI sheet networks. Systematic temperature dependent studies establish a correlation between the structure and optical exciton features. Such thermo-optic exciton switching suggests possible new photonic devices

Synthesis, structural, thermal and optical studies of inorganic-organic hybrid semiconductors, R-PbI₄

Wide varieties of naturally self-assembled two-dimensional inorganic-organic (IO) hybrid semiconductors, (4-ClC6H4NH3)2PbI4, (C6H9C2H4NH3)2PbI4, (CnH2n-1NH3)2PbI4 (where n = 12, 16, 18), (CnH2n-1NH3)2PbI4 (where n = 3, 4, 5), (C6H5C2H4NH3)2PbI4, NH3(CH2)12NH3PbI4, and (C4H3SC2H4NH3)2PbI4, were fabricated by intercalating structurally diverse organic guest moieties into lead iodide perovskite structure. The crystal packing of all these fabricated IO-hybrids comprises of well-ordered organic and inorganic layers, stacked-up alternately along c-axis. Almost all these hybrids are thermally stable up to 200 °C and show strong room-temperature exciton absorption and photoluminescence features. These strongly confined optical excitons are highly influenced by structural deformation of PbI matrix due to the conformation of organic moiety. A systematic correlation of optical exciton behavior of IO-hybrids with the organic/inorganic layer thicknesses, intercalating organic moieties, and various structural disorders were discussed. This systematic study clearly suggests that the PbI layer crumpling is directly responsible for the tunability of optical exciton energy

Naturally Self-Assembled Nanosystems and Their Templated Structures for Photonic Applications

Self-assembly has the advantage of fabricating structures of complex functionalities, from molecular levels to as big as macroscopic levels. Natural self-assembly involves self-aggregation of one or more materials (organic and/or inorganic) into desired structures while templated self-assembly involves interstitial space filling of diverse nature entities into self-assembled ordered/disordered templates (both from molecular to macro levels). These artificial and engineered new-generation materials offer many advantages over their individual counterparts. This paper reviews and explores the advantages of such naturally self-assembled hybrid molecular level systems and template-assisted macro-/microstructures targeting simple and low-cost device-oriented fabrication techniques, structural flexibility, and a wide range of photonic applications.</jats:p

Structural and optical studies of local disorder sensitivity in natural organic–inorganic self-assembled semiconductors

The structural and optical spectra of two related lead iodide (PbI) based self-assembled hybrid organic–inorganic semiconductors are compared. During the synthesis, depending on the bridging of organic moiety intercalated between the PbI two-dimensional planes, different crystal structures are produced. These entirely different networks show different structural and optical features, including excitonic bandgaps. In particular, the modified organic environment of the excitons is sensitive to the local disorder both in single crystal and thin film forms. Such information is vital for incorporating these semiconductors into photonic device architectures

Quality of life and its determinants in people living with Human Immunodeficiency Virus infection in Kannur District, Kerala

Introduction: The prevalence of Human Immunodeficiency Virus (HIV) infection in India is on decline. Since the introduction of Anti Retroviral Therapy, the survival of HIV positives has improved a lot. HIV/acquired immunodeficiency syndrome (AIDS) is now a chronic yet manageable disease. However, social factors like stigma and discrimination still exist, affecting the quality of life (QoL) of people living with HIV (PLHIV)/AIDS. The objectives of the study were to assess the QOL among HIV-positive patients using the World Health Organization-QOL BREF (WHO-QOL BREF) questionnaire, the factors determining the QoL of HIV-positive patients, and the stigma and discrimination faced by HIV positives in the medical field. Methods: A cross-sectional study was done during the study period of 1 year. A total of 150 PLHIV from Kannur district in Kerala participated in the study. The WHO-QOL BREF, Scale and the HIV stigma scale were used to collect the data. Results: The QoL score found in the study was 15.36 ± 2.18, 2.18. The overall QoL was influenced by education, the Stigma Scale score, having a constant income or an increased income after diagnosis, and a Perceived Social Support Scale score. The study also found that 22% (33) of the participants faced stigma and discrimination from the medical field in one form or another. Conclusion: The study found that the QOL of PLHIV in the Kannur district of Kerala revealed no difference between men and women. The determinant factors for QOL were found to vary in each domain. Education was found to have a negative impact on QOL

Genotoxic effects of silver amalgam and composite restorations: Micronuclei-Based cohort and case–control study in oral exfoliated cells

Context: A huge number of people carry dental fillings which contain either mercury-based amalgam and/or the recently introduced methacrylate-based resins. It has been shown that both these materials are known to be leached into the oral cavity and induce genotoxic alterations in the buccal mucosal cells. Because of its low cost and ease of manipulation, dental amalgam is still widely used as a restorative material in developing countries. The health risks associated with the components of this restorative material has always been a matter of concern. The present study was designed to assess the frequency of micronuclei (MN) in oral mucosal cells as it is a promising tool for studying the genotoxic effect of clastogenic agents on them. Aims: The aim of this study is to evaluate the genotoxic effects of silver amalgam and composite restorations by measuring the mean number of MN in oral exfoliated cells. Materials and Methods: The present study was a prospective cohort study which includes a study group consisting of 110 participants. The study sample was equally divided into 55 participants requiring only amalgam restoration and 55 participants requiring only composite restoration in any permanent molar teeth. The same participants before the restoration formed the control group. Smears were obtained from each patient before and 10 days after restoration and were stained with DNA-specific Feulgen stain. The number of cells containing MN out of 500 cells were counted and recorded. After the evaluation of the slides, the results were compiled and subjected to statistical analysis. Results: There was a statistically significant (P < 0.01) variation in the mean number of MN after the restoration in both amalgam (5.41 ± 1.25) and composite (2.83 ± 0.85) restorations when compared to before the restoration. However, the mean number of MN in composite restoration was significantly less when compared to amalgam restoration. There was also a statistically significant difference in the mean number of MN in subjects with single restoration when compared with multiple restorations in both amalgam and composite restorations. Conclusions: The observations from the present study showed the genotoxic effect of amalgam and composite restorations on the oral cavity. However, composite restorations were least cytotoxic when compared to amalgam restoration. Future research and technical advancements are needed for developing safer materials for use in humans