Jameesh Keloth

Optical nanofiber cavity research has mainly focused on the fundamental mode. Here, a Fabry–Pérot fiber cavity with an optical nanofiber supporting the higher-order modes (TE₀₁, TM₀₁, HE₂₁ ^o , and HE₂₁ ^e ) is demonstrated. Using cavity spectroscopy, with mode imaging and analysis, we observed cavity resonances that exhibited complex, inhomogeneous states of polarization with topological features containing Stokes singularities such as C-points, Poincaré vortices, and L-lines. In situ tuning of the intracavity birefringence enabled the desired profile and polarization of the cavity mode to be obtained. We believe these findings open new research possibilities for cold atom manipulation and multimode cavity quantum electrodynamics using the evanescent fields of higher-order mode optical nanofibers.

We study the generation of frequency nondegenerate correlated photon pairs and heralded single photons via spontaneous four-wave mixing (SFWM) in a series of identical micro- or nanofibers (MNFs). Joint spectral intensity of the biphoton field generated at wavelengths of about 880 and 1310 nm has been measured under excitation by 100-ps laser pulses demonstrating good agreement with the theoretical prediction. The measured zero-time second-order autocorrelation function was about 0.2 when the emission rate of the heralded photons was of 4 Hz. The MNF-based source perfectly matches standard single-mode fibers, which makes it compatible with the existing fiber communication networks. In addition, SFWM observation in a series of identical MNFs allows for increasing the generation rate of single photons via spatial multiplexing.

We show that coherent interaction between two sets of multiple resonances leads to exotic resonant effects, such as Fano-type resonances, optical analogue of electro-magnetically induced transparency, and avoided crossing between modes, under different coupling regimes. We experimentally demonstrate such resonant effects in a photonic crystal nanofiber cavity using two sets of cavity modes with orthogonal polarizations. The interaction between the modes arises due to intra-cavity polarization mixing. The observed line shapes are reproduced using a multiple-mode interaction model. Such spectral characteristics may further enhance the capabilities of the nanofiber cavity as a fiber-in-line platform for nanophotonics and quantum photonics applications.

We report the fabrication of a centimeter-long cavity directly on the nanofibe using femtosecond laser ablation. The cavity can operate in both “strong-coupling” and “Purcell” regime of cavity QED with moderate finesse high cooperativity and high transmission. The high optical quality of the cavity modes show promising avenues for fibe-based quantum interface and single photon sources.

We report the fabrication of a 1.2 cm long cavity directly on a nanofiber using femtosecond laser ablation. The cavity modes with finesse values in the range of 200–400 can enable the “strong-coupling” regime of cavity QED, with high cooperativity of 10–20, for a single atom trapped 200 nm away from the fiber surface [Phys. Rev. A 80, 053826 (2009) [CrossRef] ]. Such cavity modes can still maintain the transmission between 40%–60%, suggesting a one-pass intracavity transmission of 99.53%. Other cavity modes, which can enable cooperativity in the range of 3–10, show transmission over 60%–85% and are suitable for fiber-based single-photon sources and quantum nonlinear optics in the “Purcell” regime.

We present a protocol for fabricating 1-D photonic crystal cavities on subwavelength diameter silica fibers (optical nanofibers) using...

We demonstrate a method for making precise measurements of the diameter of a tapered optical fiber with a sub-wavelength diameter waist (an optical nanofiber). The essence of the method is to create a composite photonic crystal cavity by mounting a defect-mode grating on an optical nanofiber. The resultant cavity has a resonance wavelength that is sensitive to the nanofiber’s diameter, allowing the diameter to be inferred from optical measurements. This method offers a precise, nondestructive, and in situ way to characterize the nanofiber diameter.

We demonstrate enhanced light-matter interaction in nanofiber based photonic crystal cavity. We show the absorption of the guided mode can be enhanced up to 53% for an average atom number of 4.7 around nanofiber cavity.