Metal-halide perovskites are promising optical gain materials because of their excellent photophysical properties. Recently, large perovskite single crystals with phase purity, less defects, and over millimeter dimensions have been successfully synthesized. However, the optical gain effect from these large-size single crystals has not yet been realized. Herein, we for the first time report efficient two-photon pumped amplified spontaneous emission (ASE) from millimeter-sized CsPbBr 3 single crystals (SCs) with a low threshold of 0.65 mJ cm −2 and an optical gain of 38 cm −1 . Furthermore, the CsPbBr 3 SCs also exhibit ultrastable ASE under continuous laser irradiation for more than 40 h (corresponds to 1.5 × 10 8 laser shots) at ambient condition. This work suggests the potential application of large-size perovskite single crystals in practical nonlinear optical devices.
In optically pumped laser systems, rare gas lasers (RGLs) are a field of great interest for researchers. Gas laser regimes with metastable Ne, Ar, and Kr atoms have been investigated, while studies of RGLs based on metastable Xe are sparse. In this work, when a strong excitation laser (2.92 mJ/pulse, 7.44 × 10 W/cm) was applied to excite Xe atoms from the ground state to the 6p[1/2] state, an interesting phenomenon emerged: An intense fluorescence of 980 nm (6p[1/2]-6s[3/2]) was produced. However, when the energy of excitation laser was decreased to 0.50 mJ/pulse (1.27 × 10 W/cm), the fluorescence of 980 nm became very weak. Besides, lifetime and decay rate constant of the 6p[1/2] state under the condition of E = 2.92 mJ are significantly different from either those measured by other groups or those of E = 0.50 mJ. These phenomena indicate that the high energy of excitation laser should trigger some new kinetic mechanisms. Further works identified that the new kinetic mechanism is the MIR ASE of 3408 nm (6p[1/2]-6s'[1/2]). The mechanisms are proposed as follows. Substantial 6p[1/2] atoms are produced by laser excitation. Then, the ASE of 3408 nm (6p[1/2]-6s'[1/2]) is quickly produced to populate substantial 6s'[1/2] atoms. The 6s'[1/2] atoms can readily arrive at the 6p[1/2] states through collision by virtue of the small energy difference (84 cm) and high collision rate constant of the transition from the 6s'[1/2] state to the 6p[1/2] state. As a result, the intense fluorescence of 980 nm is generated.
Purpose:This study aimed to investigate the outcomes of permanent Iodine-125 (125I) radiotherapy for patients with unresectable retroperitoneal malignant tumor.Methods:Twenty-six patients with retroperitoneal malignant tumors were implanted with 125I seeds under ultrasound guidance from June 2012 to June 2015. The patients were then followed up for 3 to 36 months after the implantation. During the follow-up, pain relief, control of tumor growth, over survival rate, and complications were evaluated.Results:Most of the patients (90%, 24/26) suffered from mild to severe pain before 125I seed treatment. After 1-month treatment, 16 patients had 100% pain relief, 4 patients had at least 50% pain relief, and 4 patients had no response, showing 83.3% of pain relief response. Results of computed tomography scan after 2-month 125I treatment indicated that 3 patients had complete remission in the tumor size, 20 patients had partial remission in tumor size, 2 patients were stable, and 1 patient had progressive disease, accounting for 88.4% response in tumor size remission. The median survival of the 26 patients was 11 months. The 1-year and 2-year overall survival rates were 46% and 27%, respectively. The median survival of the 5 patients with pancreatic cancer was 9.4 months. None of the patients had any severe complications.Conclusions:
125I implantation could effectively relieve the pain in the patients with advanced primary or metastatic retroperitoneal malignant tumors and suppress local tumor progress.
Plasmonic
SLR (surface lattice resonance) has sharp and intense
extinction or absorption peaks, which facilitates a variety of optical
and spectral applications, e.g., optical filters, absorbers, reflectors,
sensors, etc. In this work, we propose a plasmonic array pair structure
composed of two stacked finite square array panels. By twisting it,
its plasmonic SLR changes, since the break of periodicity alters the
inter-layer plasmonic coupling. Numerical simulation is carried out
using the DDA (discrete dipole approximation) method. Simulation results
show that its optical properties such as extinction spectra/absorption
spectra change dramatically when the two-layer structure is twisted
by only a small angle. More interestingly, two resonance peaks at
different wavelengths show an inverse trend while twisting, one gets
lower and broader, while the other gets higher and narrower. Dipole
mapping of amplitude and phase is checked to reveal the plasmonic
coupling under twist. The influence of environment/material permittivity
on spectra is also examined. Results introduced in this work may work
as a scientific tool to reveal more properties of plasmonic SLR and
can serve as an angle sensor, tunable optical filter, chiral sensor,
etc.
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