Microlaser Output from Rare‐Earth Ion‐Doped Nanocrystal‐in‐Glass Microcavities

Abstract

of photons near a circular ring boundary via successive total internal reflections, whispering gallery mode microcavities exhibit ultrahigh Q factors and extremely small mode volumes, leading to greatly enhanced light-matter interactions. [2][3][4] These superior characteristics make WGM microcavities highly attractive for on-chip optical communications, including microlaser sources, [5,6] active filters, [7] optical sensors, [8,9] and others. Using WGM microcavities as resonant cavities for laser oscillations, the light energy density in microcavities is quite high, which results in the reduction of laser thresholds down to the microwatt range. [10][11][12] With an extremely high quality factor and facile processability, inorganic glasses are the most reliable materials for building WGM lasers. In the 1990s, near-infrared lasers were demonstrated in Nd 3+ -doped glass microspheres. [12] Since then, using amorphous glass microcavities to generate lasers with RE-ions has been well established. [11,[13][14][15] Furthermore, various kinds of lasers, such as Raman lasers [16] and second harmonics, [17,18] have been developed by applying glass WGM resonators. However, unlike crystals, glasses are amorphous, and they are characterized by relatively large phonon energy and broad phonon energy distribution, which are detrimental to the luminescence of rare earth (RE) ions that serve as the emission centers. Combining the low phonon energy of the crystalline phase with the excellent mechanical and chemical stability of the oxide matrix, the oxyfluoride nanocrystallized glass ceramic (NGC) has been regarded as an ideal host material for RE ions. [19] However, WGM laser output from NGC microcavities has not yet been reported. The main reason is that the absorption and scattering loss increase rapidly with the growth of nanocrystals in the glass matrix, resulting in the reduction of cavity Q factors that hinders low threshold laser output. To address these obstacles, we carefully designed an excellent oxyfluoride NGC material, where NaYF 4 nanocrystals are crystallized within the borosilicate glass matrix through a controlled heat-treatment process.Since the refractive index of the nanocrystal matches well with the glass matrix, and the sizes of the precipitated nanocrystals are small and uniform, the rise in absorption and scattering losses, which are very harmful to Q factors, are prevented. As a result, Er 3+ -doped NGC microsphere cavities with Q factors as high as 10 6 are obtained, which enables single mode WGM Nanocrystallized glass ceramics (NGCs) are important optical materials, but few studies have focused on their laser actions. Here, by precipitation of NaYF 4 nanocrystals enriched with Er 3+ ions in an oxide glass matrix, great enhancement of the luminescence properties for the NGC microspheres is realized. By carefully matching the refractive index of the glass matrix with that of the NaYF 4 nanocrystals and controlling the size and distribution of the precipitated nanocrystals, the absorption and Rayleigh scat...

Enhanced CW Lasing and Q‐Switched Pulse Generation Enabled by Tm3+‐Doped Glass Ceramic Fibers

“…Clearly, the average grain size presents a significant increase from 11 to 24 nm as the crystallization temperature rises from 385 to 395 °C. Based on the Rayleigh scattering model, [ 38 ] the optical transmittance of glass is inversely proportional to the crystal size; thus, the excellent light propagation performance of nanostructured fiber can be realized by appropriately regulating the grain size. To further reduce the fiber loss required for optoelectronic applications, the core and cladding compositions should be well matched, the OH − and other impurities produced during the glass melting process should be eliminated, and the fiber‐drawing temperature and speed should be carefully optimized.…”

Tm3+/Cr3+ Codoped Dual‐Phase Transparent Glass‐Ceramics for Light Conversion in Photosynthesis

“…The precursor glasses (PGs) with the molar composition of 45SiO 2 –22Al 2 O 3 –16Na 2 CO 3 –9NaF–8YF 3 – x TmF 3 – y Cr 2 O 3 ( x = 0–2.0, y = 0–0.2) were fabricated by the conventional melt‐quenching technique. [ 22–25 ] Briefly, the raw materials including SiO 2 (99.99%), Al 2 O 3 (99.99%), Na 2 CO 3 (99.99%), NaF (99.99%), YF 3 (99.99%), TmF 3 (99.99%), and Cr 2 O 3 (99.99%) were mixed in the corundum crucible and melt at 1550 °C for 1 h. The glass melt was quenched on the stainless steel plate at 300 °C, with subsequent annealing at 500 °C for 4 h to release internal stress. The resulted PG was then heat treated at 670 °C for 2 h within a heating rate of 5 °C min −1 to obtain dual‐phase GC.…”

Fiber Optofluidic Microlasers: Structures, Characteristics, and Applications

“…[33] Doping gain medium into COF is also an efficient way to perform lasing (Right, Figure 4a). [108][109][110] Polymers including polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA) and polydimethylsiloxane (PDMS) are attractive frame materials to perform FOFLs. [111][112][113] In 2019, Chen et al fabricated a PM597-doped polymer fiber with a diameter down to 8.8 μm by electrospinning, which is a simple and low cost technology to realize the mass-production of dye-doped fiber.…”