We report on high efficency 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.
We investigate the design, fabrication and experimental characterization of high Quality factor photonic crystal nanobeam cavities in silicon. Using a five-hole tapered 1D photonic crystal mirror and precise control of the cavity length, we designed cavities with theoretical Quality factors as high as 14 million. By detecting the cross-polarized resonantly scattered light from a normally incident laser beam, we measure a Quality factor of nearly 750,000. The effect of cavity size on mode frequency and Quality factor was simulated and then verified experimentally.
We describe the design, fabrication, and spectroscopy of coupled, high Quality (Q) factor silicon nanobeam photonic crystal cavities. We show that the single nanobeam cavity modes are coupled into even and odd superposition modes, and we simulate the frequency and Q factor as a function of nanobeam spacing, demonstrating that a differential wavelength shift of 70 nm between the two modes is possible while maintaining Q factors greater than 10^6. For both on-substrate and free-standing nanobeams, we experimentally monitor the response of the even mode as the gap is varied, and measure Q factors as high as 200,000.
Quantum photonics technologies require a scalable approach for integration of non-classical light sources with photonic resonators to achieve strong light confinement and enhancement of quantum light emission. Point defects from hexagonal Boron Nitride (hBN) are amongst the front runners for single photon sources due to their ultra bright emission, however, coupling of hBN defects to photonic crystal cavities has so far remained elusive. Here we demonstrate on-chip integration of hBN quantum emitters with photonic crystal cavities from silicon nitride (Si3N4) and achieve experimentally measured Q-factor of 3,300 for hBN/Si3N4 hybrid cavities. We observed 9-fold photoluminescence enhancement of a hBN single photon emission at room temperature. Our work paves the way towards hybrid integrated quantum photonics with hBN, and outlines an excellent path for further development of cavity quantum electrodynamic experiments and on-chip integration of 2D materials.
Wavelength-scale, high Q-factor photonic crystal cavities have emerged as a platform of choice for on-chip manipulation of optical signals, with applications ranging from low-power optical signal processing and cavity quantum electrodynamics, to biochemical sensing. Many of these applications, however, are limited by the fabrication tolerances and the inability to precisely control the resonant wavelength of fabricated structures. Various techniques for post-fabrication wavelength trimming and dynamical wavelength control -- using, for example, thermal effects, free carrier injection, low temperature gas condensation, and immersion in fluids -- have been explored. However, these methods are often limited by small tuning ranges, high power consumption, or the inability to tune continuously or reversibly. In this letter, by combining nano-electro-mechanical systems (NEMS) and nanophotonics, we demonstrate reconfigurable photonic crystal nanobeam cavities that can be continuously and dynamically tuned using electrostatic forces. A tuning of ~10 nm has been demonstrated with less than 6 V of external bias and negligible steady-state power consumption.
We experimentally demonstrate high Quality factor dual-polarized TE-TM photonic crystal nanobeam cavities. The free-standing nanobeams are fabricated in a 500 nm thick silicon layer, and are probed using both tapered optical fiber and free-space resonant scattering set-ups. We measure Q-factors greater than 10^4 for both TM and TE modes, and observe large fiber transmission drops (0.3 -- 0.4) at the TM mode resonances.