Active nanowaveguides in polymer doped with CdSe-ZnS core-shell quantum dots

Energy Dissipation and Asymmetric Excitation in Hybrid Waveguides for Routing and Coloring

The delivery of optical signals from an external light source to a nanoscale waveguide is highly important for the development of nanophotonic circuits. However, the efficient coupling of external light energy into nanophotonic components is difficult and still remains a challenge. Herein, we use an external silica nanofiber to light up an organic-inorganic hybrid nanowaveguide, namely, a system composed of a polymer filament doped with MoS₂ quantum dots. Nanofiber-excited nanowaveguides in a crossed geometry are found to asymmetrically couple excitation signals along two opposite directions, with different energy dissipation resulting in different colors of the light emitted by MoS₂ quantum dots and collected from the waveguide terminals. Interestingly, rainbow-like light in the hybrid waveguide is achieved by three-in-one mixing of red, green, and blue components. This heterodimensional system of dots in waveguide represents a significant advance toward all-optical routing and full-color display in integrated nanophotonic devices.

Optical waveguiding properties of colloidal quantum dots doped polymer microfibers

QDs-doped polymer microfibers are fabricated through direct drawing method. By adding the polymethylmethacrylate into polystyrene, the surface quality and flexibility of microfiber are improved. Under direct excitation by the focused laser, the polymer microfibers doped with different quantum dots emit different colors and act as an optical waveguide. The waveguide properties of the microfiber are studied in detail. It is found that refractive index of the substrate and diameter of microfiber are the most important factors that affect the optical loss of this waveguide. The microfiber does not produce significant polarization after being deposited on the substrate. Moreover, exciting the QDs-doped polymer microfiber through a blue LED is demonstrated. This structure may find widespread applications in integrated photonic devices.

Dispersing upconversion nanocrystals in PMMA microfiber: a novel methodology for temperature sensing

The synthesis of a β-NaYF₄:Yb³⁺/Tm³⁺ phosphor by a thermal decomposition method, focusing on the fabrication of microfibers by the co-doping of nanocrystals with PMMA solution.

Spectral and spatial characterization of upconversion luminescent nanocrystals as nanowaveguides

Lanthanide upconversion (UC) luminescent nanocrystals exhibit a uniquely sharp multiband emission over a broad spectral bandwidth covering the ultraviolet region to the near-infrared (NIR) region when subjected to NIR excitation, which is vital for multichannel optical communication using wavelength-division multiplexing to achieve high transmission rates. In this study, we experimentally and theoretically investigated the spectral and spatial characterization of a single NaYF₄:Yb³⁺,Tm³⁺(Yb³⁺,Er³⁺) UC nanocrystal as a nanowaveguide. We suggest that a UC nanocrystal can be used as a nanowaveguide because it produces a range of output colors simultaneously and provides unaltered emission bands during propagation. Via the observation of single NaYF₄:Yb³⁺,Tm³⁺(Yb³⁺,Er³⁺) UC nanocrystals, we found, for the first time, that a single UC nanocrystal exhibited wavelength- and position-dependent UC emissions. In addition, by adding Ag coating to the UC nanocrystal to act as a plasmonic waveguide and introducing a photonic crystal, the scattering loss of the UC emissions was significantly suppressed in the middle of the NaYF₄ nanocrystal, indicating efficient light guiding through the UC nanocrystal. Our discovery provides a basic understanding of the use of UC nanocrystals as nanowaveguides at the single-nanoparticle level, expanding our knowledge of the performance optimization of UC nanomaterials.

Temperature sensing using CdSe quantum dot doped poly(methyl methacrylate) microfiber

This work describes noncontact temperature measurements using wavelength shifts of CdSe quantum dot (QD) doped poly(methyl methacrylate) microfiber. The sensor is fabricated using a drawing method by bridging two tapered single mode fibers with a polymer microfiber (PMF) approximately 3 μm in diameter. A set of a PMF section with and without the doping of the CdSe-ZnS core-shell QD was applied as sensing probes and used to measure temperatures over the range of 25°C-48°C. The experimental results show that the doped PMF is able to achieve a higher performance with a reasonably good sensitivity of 58.5 pm/°C based on the wavelength shifting, which is about 18 times that of the undoped PMF temperature sensitivity. The proposed sensor showed a linear temperature sensing range that matches well with the physiologically relevant temperatures. Moreover, these results open the way for long-term and high-stability realization of temperature sensing optical fibers.

Dispersing upconversion nanocrystals in a single silicon microtube

Nanocrystals of Ln³⁺ (Ln = Yb, Tm and Ho) doped β-NaLuF₄ with average diameter about 200 nm are dispersed in silica-based microtube (MT) by a simple flame heating method. The fabricated microtube has a diameter range from 2 μm to 30 μm and lengths up to hundreds microns. The fluorescence of upconversion nanocrystals (UCNCs) can propagate along a single MT and couple into another MT through evanescent field. The guiding performance of the single UCNCs doped MT is measured to prove that it can be used as an active waveguide. Moreover, optical temperature sensing based on the single UCNCs-MT is also demonstrated, and the sensitivity of UCNCs-MT is significantly enough for thermometry applications in the range of 298–383 K.

Efficient active waveguiding properties of Mo6 nano-cluster-doped polymer nanotubes

We investigate 1D nanostructures based on a Mo6@SU8 hybrid nanocomposite in which photoluminescent Mo6 clusters are embedded in the photosensitive SU8 resist. Tens of micrometers long Mo6@SU8-based tubular nanostructures were fabricated by the wetting template method, enabling the control of the inner and outer diameter to about 190 nm and 240 nm respectively, as supported by structural and optical characterizations. The image plane optical study of these nanotubes under optical pumping highlights the efficient waveguiding phenomenon of the red luminescence emitted by the clusters. Moreover, the wave vector distribution in the Fourier plane determined by leakage radiation microscopy gives additional features of the emission and waveguiding. First, the anisotropic red luminescence of the whole system can be attributed to the guided mode along the nanotube. Then, a low-loss propagation behavior is evidenced in the Mo6@SU8-based nanotubes. This result contrasts with the weaker waveguiding signature in the case of UV210-based nanotubes embedding PFO (poly(9,9-di-n-octylfluorenyl-2,7-diyl)). It is attributed to the strong reabsorption phenomenon, owing to overlapping between absorption and emission bands in the semi-conducting conjugated polymer PFO. These results make this Mo6@SU8 original class of nanocomposite a promising candidate as nanosources for submicronic photonic integration.

Excitation of surface plasmons from silver nanowires embedded in polymer nanofibers

We report an excitation of surface plasmons in silver nanowires (AgNWs) which were embedded in flexible polymer nanofibers. Using waveguiding excitation, surface plasmons in AgNWs were excited and propagated. By directing light of 650, 532, and 473 nm wavelengths into the nanofiber, surface plasmons in an embedded single AgNW (average diameter 400 nm, length 4.3 μm) were excited and the corresponding propagation lengths for the three wavelengths are 10.6, 7.7, and 5.1 μm. It was also found that, when a spatially incoherent white light of a halogen lamp with an excitation optical power of 80 μW was coupled into the polymer nanofiber, a surface plasmon mediated interference fringe was observed. In addition, on the basis of surface plasmon excitation, two adjacent AgNWs embedded in the polymer nanofibers were demonstrated to serve as coupled plasmonic waveguides.

Photobleaching induced time-dependent light emission from dye-doped polymer nanofibers

Photobleaching induced time-dependent light emission at different positions along dual-dye-doped polymer nanofibers.

Light transfer from quantum-dot-doped polymer nanowires to silver nanowires

The plasmons of two silver nanowires are simultaneously excited by photoluminescence of the quantum-dot-doped nanowire under 532 nm laser excitation.

Laser Emission from Ring Resonators Formed by a Quantum-Dot-Doped Single Polymer Nanowire

Laser emission from nanowire-based devices is important for nanophotonic applications. Here we report the observation of optically pumped laser emission from ring resonators formed by quantum-dot-doped single polymer nanowire. By assembling a 500 nm diameter single polymer nanowire with an optical loss coefficient of 70 cm^-1 to form a ring resonator with a short diameter of 20 μm and a large diameter of 40 μm, multimode laser emission with mode number of 9 is obtained in the wavelength region from 550 to 650 nm. The dominant emission is 600 nm wavelength with a line width of 0.8 nm, a Q factor of 400, and a low lasing threshold of 100 μJ/cm² under a 550 nm green laser pump.

Gold nanorod-enhanced light emission in quantum-dot-doped polymer nanofibers

One-dimensional nanomaterials have attracted great interest in both fundamental research and technological applications because they can function as device elements and be used to effectively generate, guide, and detect light. Here we report a gold nanorod-enhanced light emission in quantum-dot-doped polymer nanofibers. By incorporating gold nanorods into quantum-dot-doped polymer nanofiber, a 67% increment in 600 nm red light emission efficiency was obtained with an extinction coefficient of 100 cm(-1), a low excitation power operation of 100 nW, and a 100 min increment in photostability.

Thermally tunable amplified spontaneous emission from Cu2ZnSnS4 quantum dot doped photonic cavity by a soft solvothermal route

In this article, non-toxic Cu₂ZnSnS₄ quantum dots (CZTSQDs) were synthesized by the solvothermal method and then embedded into a photonic cavity to tune the amplified spontaneous emission.

Wavelength-converted wave-guiding in dye-doped polymer nanofibers

Nanoscale wavelength-converted optical components are promising components for communication and optical information processing in integrated photonic system. In this work, we report a facile strategy for realizing continuously tunable wavelength-converted wave-guiding in dye-doped nanofibers. The nanofibers with diameters of 200–800 nm have an absorption coefficient of about 80 cm⁻¹ and a self-absorption coefficient of about 30 cm⁻¹, and exhibit relatively high PL efficiency and high photobleaching resistance under an optical pump. By launching the pump light into the nanofibers, the excited light in the nanofibers got self-absorption and reemitted at a longer wavelength, resulting in a gradual wavelength conversion during propagation. On the basis of this wavelength-converted wave-guiding, nanoscale wavelength-converted splitters were demonstrated by assembling the nanofibers into crossed structures. We believe that the dye-doped nanofibers would bring new exciting opportunities in developing new wavelength-converted optical components for nanophotonic device integration.