To realize the refractive index dispersion accurately is essential for the design of optical devices. In this paper, we study hexagonal ZnO microrod cavities. We measure angle-resolved ...photoluminescence and use an iterative method to derive the refractive index dispersion near the band edge. Because of the large exciton binding energy in bulk ZnO, the photogenerated excitons are stable at room temperature. As a result, excitons could significantly affect the refractive index dispersion near the resonance energy. Thus, we construct a modified Lorentz oscillator model to extract the transverse and longitudinal exciton resonance energy and the damping term due to the scattering between LO-phonons and excitons at room temperature. The Rabi splitting energy and zero detuning point obtained by this method are reliable. The dispersion relations of polaritons measured by our angle-resolved photoluminescence agree well with the dispersion relation of polaritons, deduced by using the refractive index dispersion and optical parameters obtained by our theoretical model, thus, lending support to our theoretical model and the extracted parameters.
Random Laser Emission from Fiber coated ZnO Ali, Abdullah Taha; Wan Ahmad Kamil, Wan Maryam; Wu, Sheng-Chan ...
Journal of physical science,
01/2023, Volume:
34, Issue:
2
Journal Article
Open access
Random lasing from a solid-state gain medium prepared on photonic crystal fibre (PCF) is observed for the first time. Vertically aligned ZnO microrods were prepared on PCF using a simple technique of ...chemical bath deposition (CBD). A low lasing threshold of 12.2 mJ/cm2 was observed in sample with longer zinc oxide (ZnO) rod length. The variation in morphology and population density did not affect the lasing threshold significantly. Further investigation of the effect of fiber length revealed that a shorter fiber had a lower threshold and showed quenching of the spontaneous emission revealing better lasing output. Simulations based on the morphology of the gain medium revealed light confinement in the structure, validating the origin of the lasing emission. Overall, this study shows the potential of utilising optical fiber as random lasers with a sustainable solid state gain medium.
We measure the optical model gain of single Zinc Oxide microrod by Variable Stripe Length method. The pick value of gain spectra in room temperature is well below the bandgap of bulk ZnO, which comes ...from exciton-exciton scattering, and it can be as a reference for the design of UV-devices.
Abstract
The soft and polar nature of quasi‐2D (PEA)
2
PbBr
4
perovskite, and robust photo‐generated excitons lead exciton‐polaritons and exciton‐polarons as the important phenomena near the band ...edge for application in the lighting aspect. In this work, a convenient methodology is proposed based on the polariton resonant modes in temperature‐dependent (77 K to RT) spectroscopy, and investigate the effect of these quasi‐particles on refractive index dispersion. The large binding energy (≈335 meV) of quasi‐2D excitons is obtained by the reflectance measurements at 77 K. Stable exciton‐polaritons and exciton‐polarons are confirmed by energy dispersions and the observation of self‐trapped exciton‐polaron state, respectively. Furthermore, the large negative thermal‐optic coefficient due to damping effect of exciton‐phonon scattering is observed. The phenomenon is opposite to those observed in conventional semiconductors (e.g., Si, Ge, GaN, AlN, GaAs, AlAs, and ZnO etc.). The observed stable negative thermal‐optic coefficients from 160 K to RT indicate that the quasi‐2D perovskite can be used as a phase compensator for conventional semiconductor materials.
Methylammonium lead bromide perovskite (MAPbBr3)-embedded nano- and micro-fibers are successfully fabricated by using the uniaxial electrospinning technique. Through the study of solidification and ...coordination between perovskite with hybrid polymers, polymethyl methacrylate, and polyacrylonitrile, the bamboo-like perovskite-embedded polymer nano/microfibers are unpredictably formed. Encapsulated in polymer, the passive perovskite-embedded polymer fibers exhibit a long-term fluorescence performance when simultaneously exposed to both water immersion and short-wavelength laser irradiation. Notably, due to the efficient gain media, the perovskite-rich region of the electrospun fiber can act as an optical microcavity. Multi-mode and single-mode lasing behaviors can be achieved via different cavity lengths. The mechanism of a microlaser within this perovskite fiber is confirmed through a Fabry–Pérot cavity, which provides an opportunity for optical components in lasers.
Abstract
Constructing polaritonic devices in monolithic, ultra‐compact photonic architectures with monolayer‐featured exciton‐emitters is decisive to exploit the coherent superposition between ...entangled photonic and excitonic eigenstates for potential realizations of optical nonlinearities, macroscopic condensations, and superfluidity. Here, a feasible strategy for exciton‐polariton formations is demonstrated by implementing a Tamm‐plasmon (TP) polaritonic device with the active material composed of single‐monolayered perovskite (CsPbBr
3
) quantum dots (QDs). The metallic character of the TP configuration is able to concentrate its resonance mode into a confined region beyond the diffraction limit, which highly overlaps, both spatially and spectrally, with the single‐monolayered CsPbBr
3
QDs embedded inside. The mode volume of the device is hence reduced dramatically, leading to an enhanced light–matter coupling strength for the polaritonic emission at room temperature. In particular, it is found that the dispersion relation of the TP polaritonic device is tunable by detuning the excitonic and photonic eigenmodes and that the polariton–polariton interaction energy is strongly dependent on the polariton's spin state. The presented strategy is a determinant step toward the realization of strong light–matter coupling and polariton spintronics in the CsPbBr
3
QDs with a single‐monolayered feature.
AIM： To study Helicobacter pylori （H pylori） infection in relation to E-cadherin （E-cad） promoter polymorphism and hypermethylation in GCs. METHODS： Specimens were taken from representative cancerous ...lesions and adjacent non-cancerous epithelia of 67 resected GCs. Hpyloriwas detected by real-time PCR of the cagA gene from non-neoplastic epithelium. E-cadpromoter polymorphism and hypermethylation were determined by restriction fragment length polymorphism analysis and methylation-specific PCR, respectively. Expression of E-cadprotein was determined by immunohistochemistry. RESULTS： Hpyloriwas found in 57% of patients with GC. Hpyloriinfection was more frequently found in tumors with the -160C/C genotype than those with the -160C/A and -160A/A genotypes （74% vs 47%, P = 0.02）. Hpylori infection was associated with E-cad methylation in nonneoplastic epithelium; however, no significant difference in H pylori was observed between methylated and unmethylated cancerous lesions. CONCLUSION： Patients with the -160C/C genotype might require H pyloriinfection to promote the inactivation of CDH1, suggesting that Hpyloriinfection might affect GC in an initial stage because polymorphism is germ line. Mechanism of hypermethylation of CDH1 promoter in GC is complex, and Hpyloriinfection might affect it in an initial stage.
Circulating tumor cells (CTCs) are associated with breast cancer prognosis. Research is limited regarding the role of circulating cancer stem-like cells (cCSCs) considering the treatment response and ...survival among patients with metastatic breast cancer. Accordingly, we performed this prospective study to clarify the prognostic significance of baseline cCSCs for metastatic breast cancer in terms of first-line chemotherapy.
Between April 2014 and January 2016, we prospectively enrolled 48 patients with stage IV breast invasive ductal carcinoma who underwent first-line chemotherapy. We identified and analyzed CTCs and cCSCs by using a protocol based on negative selection and flow cytometry before chemotherapy. CTCs were identified as EpCAM
Hoechst
CD45
cells and cCSCs as CD133
EpCAM
Hoechst
CD45
cells. cCSCs were expressed as a percentage of CTCs. The associations between CTCs, cCSCs, and the clinicopathological variables that were predictive of the treatment response and survival outcome were analyzed using univariate and multivariate analyses.
We identified CTCs in all the enrolled patients, with a median number of 33.9/mL CTCs. CSCs were isolated in 97.9% of the patients; the median percentage of cCSCs was 14.7%. A high baseline level of cCSCs was correlated with an inferior tumor response rate (54.2% vs. 95.8%, p < 0.001), overall survival (OS; median: 27.7 months vs. not reached, p < 0.001), and progression-free survival (PFS; median: 5.7 vs. 18.0 months, p < 0.001). Multivariate analysis revealed that along with other clinical variables, baseline cCSCs remained an independent prognostic factor for OS and PFS.
Baseline cCSCs predict the treatment response as well as survival in patients with metastatic breast cancer undergoing first-line chemotherapy. Therefore, the measurement of cCSCs may assist in identifying early cancer treatment response and prognosis.
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