The unique emission properties of single-walled carbon nanotubes are attractive for achieving increased functionality in integrated photonics. In addition to being room-temperature telecom-band emitters that can be directly grown on silicon, they are ideal for coupling to nanoscale photonic structures. Here we report on high-efficiency coupling of individual air-suspended carbon nanotubes to silicon photonic crystal nanobeam cavities. Photoluminescence images of dielectric- and air-mode cavities reflect their distinctly different mode profiles and show that fields in the air are important for coupling. We find that the air-mode cavities couple more efficiently, and estimated spontaneous emission coupling factors reach a value as high as 0.85. Our results demonstrate advantages of ultralow mode-volumes in air-mode cavities for coupling to low-dimensional nanoscale emitters.
Single-walled carbon nanotubes have advantages as a nanoscale light source compatible with silicon photonics because they show room-temperature luminescence at telecom-wavelengths and can be directly synthesized on silicon substrates. Here we demonstrate integration of individual light-emitting carbon nanotubes with silicon microdisk resonators. Photons emitted from nanotubes are efficiently coupled to whispering gallery modes, circulating within the disks and lighting up their perimeters. Furthermore, we control such emission by tuning the excitation wavelength in and out of resonance with higher order modes in the same disk. Our results open up the possibilities of using nanotube emitters embedded in photonic circuits that are individually addressable through spectral double resonance.
We investigate the use of guided modes bound to defects in photonic crystals for achieving double resonances. Photoluminescence enhancement by more than 3 orders of magnitude is observed when the excitation and emission wavelengths are simultaneously in resonance with the localized guided mode and cavity mode, respectively. We find that the localized guided modes are relatively insensitive to the size of the defect for one of the polarizations, allowing for flexible control over the wavelength combinations. This double-resonance technique is expected to enable the enhancement of photoluminescence and nonlinear wavelength-conversion efficiencies in a wide variety of systems.
[Purpose] Previous studies suggest that the infrapatellar-fat-pad is affected by aging
or knee osteoarthritis, and that the infrapatellar-fat-pad in knee osteoarthritis cases
may be associated with limited mobility during knee movement. This study aimed to
determine changes in the shape and volume of the infrapatellar-fat-pad between 30° and 0°
of knee extension in knee osteoarthritis cases and in young, healthy individuals, and to
characterize differences in patellar mobility, patellar tendon mobility, and length
between the groups. [Participants and Methods] We created 3D models of the
infrapatellar-fat-pad, the patellar tendon, and bones using sagittal MRI with the knee at
30° and 0°. The following four parameters were determined: (1) movement of the
infrapatellar-fat-pad; (2) infrapatellar-fat-pad volume; (3) angle and surface length of
the patellar tendon; and (4) patellar movement. [Results] Compared with the knee
osteoarthritis group, the healthy group showed (1) reduced anterior movement of the
infrapatellar-fat-pad; (2) smaller volume changes only in the infero-postero-lateral
portion; and (3) no changes in the angle of the patellar tendon to the tibial plateau
between 30° to 0°. [Conclusion] In conclusion, between 30° and 0°, (1) the
infrapatellar-fat-pad in patients with knee osteoarthritis exhibited less anterior
movement, and (2) the patellar tendon angle was diminished in patients with knee
osteoarthritis compared with those of young-healthy knees.
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