Microfiber Taper Research Articles

Progress in growth, fabrication, and characterization of semiconductor photonic crystal nanocavities

AbstractWe present the results of recent investigations into the fabrication and characterization of high‐Q, small mode volume one‐dimensional photonic crystal nanobeam cavities in Si and two‐dimensional photonic crystal slab nanocavities in GaAs. The nanobeam cavity modes are investigated in transmission by means of a microfiber taper loop apparatus. The spectral transmission profile of the cavity modes is investigated as a function of input polarization into the fiber. The Q of the cavity for different positions and orientations of the fiber taper is investigated. The results are compared to measurements by resonant scattering. The slab nanocavities are investigated by means of quantum dot photoluminescence excitation spectroscopy. We present recent progress in growth and fabrication of such slab nanocavities.

Optical microfiber coil delay line

The feasibility of a broadband, miniature, and low loss optical delay line composed of a coiled microfiber with several-micron radius is demonstrated theoretically. Under the introduced low-loss condition, the fundamental mode of the microfiber is shifted away and does not scatter from the interfaces with the central rod and adjacent turns. Dimensions of the designed 100 ns feedforward microfiber delay line containing 20 m of microfiber are 5 mm x 5 mm x 20 mm at the radiation wavelength 1.5 microm and can be much smaller for the recirculating loop delay line. These dimensions can be further optimized by varying the radii of the microfiber and coil. The predicted insertion loss of this device is approximately 0.004 dB/ns, which is two orders of magnitude smaller than the loss achieved presently for the miniature delay lines. A curved microfiber taper is proposed as a compact, low-loss, and broadband connection to this optical delay line. The taper adiabatically converts the input fundamental mode of a straight microfiber into the shifted mode of the coiled microfiber.

Radiation loss of a nanotaper: Singular Gaussian beam model

This paper presents a model of a subwavelength diameter adiabatic microfiber taper (nanotaper), which allows an asymptotically accurate solution of the wave equation. The evanescent field near the nanotaper is expressed through a Gaussian beam having a singularity at the nanotaper axis. For certain values of parameters of the nanotaper, when it has a swell in the middle and narrows down to zero at the infinity, the nanotaper is lossless. For other values, when the nanotaper has a biconical shape, it exhibits an exponentially small radiation loss, which is determined as a tunneling rate through an effective parabolic potential barrier. The latter case represents an exceptional example of the radiation loss being distributed along the length of an adiabatic nanotaper rather than being localized near focal circumferences in the evanescent field region.