As a new kind of optically pumped gaseous lasers, diode pumped metastable rare gas lasers (OPRGLs) show potential in high power operation. In this paper, a multi-level rate equation based model of OPRGL is established. A qualitative agreement between simulation and Rawlins et al.’s experimental result shows the validity of the model. The key parameters’ influences and energy distribution characteristics are theoretically studied, which is useful for the optimized design of high efficient OPRGLs.

Diode pumped alkali vapor amplifier (DPAA) is a potential candidate in high power laser field. In this paper, we set up a model for the diode double-side-pumped alkali vapor amplifier. For the three-dimensional volumetric gain medium, both the longitudinal and transverse amplified spontaneous emission (ASE) effects are considered and coupled into the rate equations. An iterative numerical approach is proposed to solve the model. Some important influencing factors are simulated and discussed. The results show that in the case of saturated amplification, the ASE effect can be well suppressed rather than a limitation in power scaling of a DPAA.

Achieving intense nearly white upconversion emission from a single β-NaYF ₄ :Yb/Er microcrystal via saturated excitation.

The presence of manganese ions (Mn2+) in Yb/Er-co-doped nanomaterials results in suppressing green (545 nm) and enhancing red (650 nm) upconversion (UC) emission, which can achieve single-red-band emission to enable applications in bioimaging and drug delivery. Here, we revisit the tunable multicolor UC emission in a single Mn2+-doped β-NaYF4:Yb/Er microcrystal which is synthesized by a simple one-pot hydrothermal method. Excited by a 980 nm continuous wave (CW) laser, the color of the single β-NaYF4:Yb/Er/Mn microrod can be tuned from green to red as the doping Mn2+ ions increase from 0 to 30 mol%. Notably, under a relatively high excitation intensity, a newly emerged emission band at 560 nm (2H9/2 → 4I13/2) becomes significant and further exceeds the traditional green (545 nm) emission. Therefore, the red-to-green (R/G) emission intensity ratio is subdivided into traditional (650 to 545 nm) and new (650 to 560 nm) R/G ones. As the doped Mn2+ ions increase, these two R/G ratios are in lockstep with the same tunable trends at low excitation intensity, but the tunable regions become different at high excitation intensity. Moreover, we demonstrate that the energy transfer (ET) between Mn2+ and Er3+ contributes to the adjustment of R/G ratio and leads to tunable multicolor of the single microrod. The spectroscopic properties and tunable color from the single microrod can be potentially utilized in color display and micro-optoelectronic devices.

Er³⁺-sensitized upconversion nanoparticles (UCNPs) have attracted great attention due to their tunable upconversion (UC) emissions, low cytotoxicity, high resistance to photobleaching and especially multiple effective excitation wavelengths. However, detailed energy conversion between Er³⁺ and Tm³⁺ ions in Y₂O₃ UCNPs is still a problem, especially under multi-wavelength and variable pulse width excitation. In this work, we successfully fabricated a series of Er³⁺-sensitized Y₂O₃ nanocrystals by a spray flame synthesis method with a production rate of 40.5 g h⁻¹. The as-prepared UCNPs are a pure cubic phase with a mean size of 14 nm. Excited by both 980 and 808 nm lasers, the tunable upconversion luminescence (UCL) from Er³⁺ ions was achieved by increasing the Er³⁺ doping concentration, co-doping Tm³⁺ ions and extending excitation pulse-width. The investigations of the lifetimes and the laser power dependence of UC emissions further support the proposed mechanism, which provides guidance for achieving effective color control in anticounterfeiting and multiplexed labeling applications. In addition, the red UC emission at about 5 mm beneath the tissue surface was observed in an ex vivo imaging experiment under the excitation of 808 nm laser, indicating that the Y₂O₃:Er³⁺/Tm³⁺ UCNPs have great prospects in further biological applications.

Photon upconversion (UC) based on self-sensitization of lanthanide-doped nanocrystals is of great importance for biological and photonic applications. Here, we report tunable multicolor display and sensitive temperature sensing in the erbium-doped CaF₂ upconversion nanocrystals (UCNCs) codoped with Tm³⁺ ions. Under the excitation of 980, 808 and 1532 nm lasers, the upconversion luminescence (UCL) color of these self-sensitized UCNCs can be manipulated from green to red efficiently and the red-to-green (R/G) UC intensity ratio is promoted remarkably as the doping Tm³⁺ ions vary from 0 to 4 mol%. Especially, we have successfully demonstrated the multicolor modulation of these UCNCs by changing the pulse width and repetition frequency under multi-wavelength excitation. The power dependence and decay lifetimes measurements of Er³⁺ ions under multi-wavelength excitation were carried out to clarify the UC color manipulation. In addition, the optical temperature sensing properties of CaF₂:Er³⁺/Tm³⁺ (10/0.125 mol%) UCNCs are also studied thoroughly under 980, 808 and 1532 nm lasers excitation, and the results show that the UCNCs possess outstanding thermal sensitivity. The features enable these UCNCs to act as promising candidates for high-resolution biological imaging, multicolor display and nanoscale thermometer fields.