SNAP microwave optical filters

If the originally flat bottom of a wide quantum well with multiple eigenstates is periodically modulated, its eigenvalues rearrange into denser groups separated by wider gaps. We show that this effect, if implemented in an elongated bottle microresonator [also called a surface nanoscale axial photonics (SNAP) microresonator] allows us to design microwave photonic tunable filters with an outstanding performance

In situ observation of slow and tunnelling light at the cutoff wavelength of an optical fiber

Slow waves and tunneling waves can meet at the cutoff wavelengths and/or the transmission band edges of optical and quantum mechanical waveguides. The experimental investigation of this phenomenon, previously performed using various optical microstructures, is challenged by fabrication imperfections and material losses. Here, we demonstrate this phenomenon in situ for whispering gallery modes slowly propagating along a standard optical fiber, which possesses a record uniformity and exceptionally small transmission losses. The slow axial propagation dramatically increases the longitudinal wavelength of light and allows us to measure nanosecond-long tunneling times along tunable potential barriers having the width of hundreds of micrometers. This demonstration paves a simple and versatile way to investigate and employ the interplaying slow and tunneling light

Rectangular SNAP microresonator fabricated with a femtosecond laser

Surface nanoscale axial photonics (SNAP) microresonators, which are fabricated by nanoscale effective radius variation (ERV) of the optical fiber with subangstrom precision, can be potentially used as miniature classical and quantum signal processors, frequency comb generators, and ultraprecise microfluidic and environmental optical sensors. Many of these applications require the introduction of nanoscale ERV with a large contrast α, which is defined as the maximum shift of the fiber cutoff wavelength introduced per unit length of the fiber axis. The previously developed fabrication methods of SNAP structures, which used focused CO2 and femtosecond laser beams, achieved α∼0.02 nm∕μm. Here we develop a new, to the best of our knowledge, fabrication method of SNAP microresonators with a femtosecond laser, which allows us to demonstrate a 50-fold improvement of previous results and achieve α∼1 nm∕μm. Furthermore, our fabrication method enables the introduction of ERV that is several times larger than the maximum ERV demonstrated previously. As an example, we fabricate a rectangular SNAP resonator and investigate its group delay characteristics. Our experimental results are in good agreement with theoretical simulations. Overall, the developed approach allows us to reduce the axial scale of SNAP structures by an order of magnitude

Angstrom-precise fabrication of surface nanoscale axial photonics (SNAP) microresonators with a flame

We demonstrate the fabrication of surface nanoscale axial photonics bottle microresonators with angstrom precision using a flame. We observe strongly unscalable behavior of the whispering gallery mode cutoff wavelengths with different radial quantum numbers along the fibre length

Offsetting self-phase modulation in optical fibre by sinusoidally time-varying phase

We report on our recent experimental and theoretical results on the use of a sinusoidally time-varying phase to suppress undesirable self-phase modulation of optical pulses propagating in fibre-optic systems

Frequency comb generation in SNAP bottle resonators

We develop a theory of optical frequency comb generation in ultra-compact surface nanoscale axial photonic (SNAP) bottle microresonators, employing the nonlinear interaction of whispering gallery modes which are confined along an optical fiber with nanoscale radius variation. We predict that a SNAP microresonator with a radius of a few micrometers can generate a frequency comb with an ultra-fine sub-gigahertz spectral spacing, which would require traditional ring resonators of centimeter radius. We identify regimes of stable or quasiperiodic comb dynamics due to soliton excitation, and show that special engineering of the SNAP radius profile can be used to compensate for nonlinearity-induced dispersion

Controlled transportation of light by light at the microscale

We show how light can be controllably transported by light at microscale dimensions. We design a miniature device that consists of a short segment of an optical fiber coupled to transversally oriented input-output microfibers. A whispering gallery soliton is launched from the first microfiber into the fiber segment and slowly propagates along its mm-scale length. The soliton loads and unloads optical pulses at designated input-output microfibers. The speed of the soliton and its propagation direction is controlled by the dramatically small, yet feasible to introduce, permanently or all-optically, nanoscale variations of the effective fiber radius

Surface nanoscale axial photonics structures introduced by bending of optical fibers

The new manufacturing method for fabrication of Surface Nanoscale Axial Photonics (SNAP) structures has been developed. We showed experimentally that the bent fiber can achieve the nanometer-scale variation in the effective fiber radius sufficient for fabrication of SNAP microresonators. The advantage of the demonstrated method is in its simplicity, robustness, and mechanical tunability of the fabricated devices