Optical Nanofibers Research Articles

Dipole and Gausson soliton for ultrashort laser pulse with high order dispersion

In this paper, we find the dipole soliton (dark-in-the bright) for higher order nonlinear Schrödinger equation (HNLSE) with kerr law. This equation represents the propagation of a nonlinear ultrashort laser pulse in the optical fiber. We use the ansatz method of Choudhuri and Porsezian to find the solitary wave solution, which is combination of product of dark and bright solitary waves. We also find single Gausson soliton solution for (HNLSE) with log law nonlinearity described in optical nano fibers.

Intrinsic transverse spin angular momentum of fiber eigenmodes

We study the transverse spin angular momentum of fiber eigenmodes. As an intrinsic property of fiber eigenmodes, it becomes considerable in optical nanofibers and, especially, increases sharply in the evanescent field. We derive analytical expressions of this angular momentum, and present its density distribution inside andoutside nanofibers. Significantly, we find the optimal ratio of the fiber core radius to the wavelength to obtain the maximum surface transverse spin. For instance, the optimal fiber radius is one fourth of the wavelength for the fundamental mode. Furthermore, we investigate the spin flow of each guided mode on the nanofiber surface and the transverse mechanical effects originated from the transverse spin on small particles.

Fabrication of 1-D Photonic Crystal Cavity on a Nanofiber Using Femtosecond Laser-induced Ablation.

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using femtosecond laser-induced ablation. We show that thousands of periodic nano-craters are fabricated on an optical nanofiber by irradiating with just a single femtosecond laser pulse. For a typical sample, periodic nano-craters with a period of 350 nm and with diameter gradually varying from 50 - 250 nm over a length of 1 mm are fabricated on a nanofiber with diameter around 450 - 550 nm. A key aspect of such a nanofabrication is that the nanofiber itself acts as a cylindrical lens and focuses the femtosecond laser beam on its shadow surface. Moreover, the single-shot fabrication makes it immune to mechanical instabilities and other fabrication imperfections. Such periodic nano-craters on nanofiber, act as a 1-D PhC and enable strong and broadband reflection while maintaining the high transmission out of the stopband. We also present a method to control the profile of the nano-crater array to fabricate apodized and defect-induced PhC cavities on the nanofiber. The strong confinement of the field, both transverse and longitudinal, in the nanofiber-based PhC cavities and the efficient integration to the fiber networks, may open new possibilities for nanophotonic applications and quantum information science.

Modal interference in optical nanofibers for sub-Angstrom radius sensitivity

Optical nanofibers (ONF) of subwavelength dimensions confine light in modes with a strong evanescent field that can trap, probe, and manipulate nearby quantum systems. To measure the evanescent field and propagating modes, and to optimize ONF performance, a surface probe is desirable during fabrication. We demonstrate a nondestructive measurement of light propagation in ONFs by sampling the local evanescent field with a microfiber. This approach reveals the behavior of all propagating modes, and because the modal beat lengths in cylindrical waveguides depend strongly on radius, simultaneously provides exquisite sensitivity to the ONF radius. We show that our measured spatial frequencies provide a map of the average ONF radius (over a 600 micrometer window) along the 10 mm ONF waist with 40 picometer resolution and high signal-to-noise ratio. The measurements agree with scanning electron microscopy (SEM) to within SEM instrument resolution. This fast method is immune to polarization, intrinsic birefringence, mechanical vibrations, scattered light, and provides a set of constraints to protect from systematic errors in the measurements

Spontaneous four-wave mixing in optical nanofibers at low temperatures

In this work, spontaneous four-wave mixing in silica optical nanofibers is studied theoretically. The spectrum of generated biphoton field and its dependence on the nanofiber temperature are analysed.

Self-organization of atoms coupled to a chiral reservoir.

Tightly confined modes of light, as in optical nanofibers or photonic crystal waveguides, can lead to large optical coupling in atomic systems, which mediates long-range interactions between atoms. These one-dimensional systems can naturally possess couplings that are asymmetric between modes propagating in different directions. Strong long-range interaction among atoms via these modes can drive them to a self-organized periodic distribution. In this paper, we examine the self-organizing behavior of atoms in one dimension coupled to a chiral reservoir. We determine the solution to the equations of motion in different parameter regimes, relative to both the detuning of the pump laser that initializes the atomic dipole-dipole interactions and the degree of reservoir chirality. In addition, we calculate possible experimental signatures such as reflectivity from self-organized atoms and motional sidebands.

Nondestructive Profilometry of Optical Nanofibers.

Single-mode optical nanofibers are a central component of a broad range of applications and emerging technologies. Their fabrication has been extensively studied over the past decade, but imaging of the final submicrometer products has been restricted to destructive or low-precision techniques. Here, we demonstrate an optical scattering-based scanning method that uses a probe nanofiber to locally scatter the evanescent field of a sample nanofibre. The method does not damage the sample nanofiber and is easily implemented by only using the same equipment as in a standard fiber-puller setup. We demonstrate the subnanometer radial resolution at video rates (0.7 nm in 10 ms) on single mode nanofibers, allowing for a complete high-precision profile to be obtained within minutes of fabrication. The method thus enables nondestructive, fast, and precise characterization of optical nanofibers, with applications ranging from optical sensors and cold atom traps to nonlinear optics.

Modal characterization of nanophotonic waveguides for atom trapping

Nanophotonic waveguides are a promising platform to trap cold atoms using red-and blue-detuned evanescent-field optical dipole forces. The asymmetric structure of integrated waveguides leads to a large birefringence that is not encountered in cylindrically symmetric optical nanofibers. We have studied both theoretically and experimentally the modal properties and suitability of silicon nitride rib waveguides for cold-atom trapping. The dependence of the modal effective index on the rib width is explored experimentally by measuring beat lengths between propagating modes. These measurements are made using a novel spatial Fourier analysis technique based on conventional far-field imaging of elastic scattering from the waveguide. We find that the beat length between the lowest order TE00 and TM00 modes is approximately 5µm, in excellent agreement with numerical calculations. We propose to take advantage of this birefringence and mode structure to create novel, one-dimensional periodic trapping potentials for atoms within the evanescent field of the waveguide.

Dominant chiral optical forces in the vicinity of optical nanofibers.

Transverse spin angular momentum (SAM) of light and associated transverse chiral optical forces have received tremendous attention recently, as the latter may lead to an optical separation of chiral biomolecules. In this context, the relative magnitude of chiral and non-chiral forces is a challenge when implementing chiral separation schemes. In this work we have demonstrated that, by spatially separating the maxima of transverse spin density from the gradient of field intensity, it is possible to dominate chiral-specific components of the force over non-chiral ones. To that end, we studied optical nanofibers and nanowires as candidates for such a scheme and demonstrated that in their vicinity, chiral optical forces can emerge that are stronger than gradient and scattering forces. This finding may be of significance in the design of improved optical separation schemes for chiral biomolecules.

Generation of pure single-photon states via spontaneous four-wave mixing in nanofibers with a variable cross section

A theory of single-photon sources of light is developed on the basis of spontaneous four-wave mixing in optical nanofibers. The spectral amplitude of the biphoton field is calculated with allowance for the real geometry of a nanofiber manufactured from standard optical fiber by heating and stretching. It is shown that by selecting pump parameters, we can simultaneously obtain the high spectral brightness and low frequency correlation of generated biphoton states in a nondegenerate mode of four-wave mixing that corresponds to single-photon states with the high purity.

Strong Magnetic Response of Optical Nanofibers

We introduce a new platform to achieve a strong magnetic response in optical fibers with nanoscale dimension. We reveal that for a coupled dipole–fiber system an electric dipole placed near an optical nanofiber can produce strong magnetic response. We show that the magnetic and electric response of such a system depends on the orientation of the dipole source with respect to the fiber. Using the multipole expansion method, we demonstrate that it is possible to suppress the electric response and preferentially enhance the magnetic resonance of a coupled dipole–fiber system, in such a way that the energy in the magnetic mode can be made 2 orders of magnitude higher than that of the electric mode of the system. This nanophotonic system opens up new possibilities to develop low-dimensional nanodevices with enhanced magnetic response.

Diameter measurement of optical nanofibers using a composite photonic crystal cavity.

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.

Rayleigh scattering in an optical nanofiber as a probe of higher-order mode propagation

Optical nanofibers provide a rich platform for exploring atomic and optical phenomena even when they support only a single spatial mode. Nanofibers supporting higher-order modes provide additional degrees of freedom to enable complex evanescent field profiles for interaction with the surrounding medium, but local control of these profiles requires nondestructive evaluation of the propagating fields. Here, we use Rayleigh scattering for rapid measurement of the propagation of light in few-mode optical nanofibers. Imaging the Rayleigh scattered light provides direct visualization of the spatial evolution of propagating fields throughout the entire fiber, including the transition from core-cladding guidance to cladding-air guidance. We resolve the interference between higher-order modes to determine local beat lengths and modal content along the fiber, and show that the modal superposition in the waist can be systematically controlled by adjusting the input superposition. With this diagnostic we can measure variations in the radius of the fiber waist to below 3 nm in situ using purely optical means. This nondestructive technique also provides useful insight into light propagation in optical nanofibers.

Effect of intrinsic surface roughness on the efficiency of intermodal phase matching in silica optical nanofibers.

We investigate the effect of intrinsic surface roughness associated to frozen thermal oscillations from the fiber fabrication process on the efficiency of third-harmonic generation via intermodal phase matching in silica nanofibers. Already a periodic wave with roughness of 0.2nm reduces the efficiency by roughly 50% in a 1-mm optical nanofiber, with the divergence growing quadratically with distance. The surface wave period does not exhibit a large impact on the efficiency, due to averaging effects. However, both the location of the surface waves with respect to the phase matching radius as well as the surface wave amplitude have substantial effect on the efficiency, with the former presenting the possibility of transferring the power back to the pump wavelength. Simulations with a realistic superposition of random surface waves indicate that the conversion efficiency increases only for a few mm of propagation and reaches a maximum of less than 1%.

単一原子/光子を操作するナノ光ファイバー(実験技術)

単一原子/光子を操作するナノ光ファイバー(実験技術)

Optical and flexible α-chitin nanofibers reinforced poly(vinyl alcohol) (PVA) composite film: Fabrication and property

In this study, α-chitin nanofibers (CNFs)–poly(vinyl alcohol) (PVA) composite films were fabricated to evaluate the compatibility and reinforcement effect of CNFs to PVA. CNFs were disintegrated by one-pass grinding and 40-min ultrasonication. The diameter of most of CNFs ranged from 30nm to 50nm. The CNFs–PVA composite films were made by immersing CNFs sheet into PVA solution. FTIR and XRD analysis revealed that there are strong interaction and good compatibility between CNFs and PVA molecular. In comparison with the neat PVA film, the light transmittance of the composite film slightly decreased from 92% to 86%. The coefficient of thermal expansion dramatically decreased from 123.62ppmK−1 to 25.09ppmK−1. The tensile strength and Young’s modulus were high to 127MPa and 5.70GPa, which were about 100% and 140% larger than those of the PVA film. The elongation at break point of the composite film decreased from 20.70% to 4.40%.

The 45th anniversary of the Institute of Spectroscopy of the Russian Academy of Sciences (Scientific session of the Physical Sciences Division of the Russian Academy of Sciences, 23 October 2013)

On 23 October 2013, the out-of-town scientific session of the Physical Sciences Division of the Russian Academy of Sciences (RAS), celebrating the 45th anniversary of the Institute of Spectroscopy, RAS (ISAN in Russ. abbr.), was held at the conference hall of the Institute's building in Troitsk.The agenda of the session, announced on the website http://www.gpad.ac.ru of the Physical Sciences Division, RAS, listed the following reports: (1) Vinogradov E A (ISAN, Troitsk, Moscow) “The main achievements of ISAN from 2009 to 2013”; (2) Balykin V I (ISAN, Troitsk, Moscow) “Atomic and photonic nanooptics”; (3) Lozovik Yu E (ISAN, Troitsk, Moscow) “Electronic and collective properties of topological isolators”; (4) Yevdokimov Yu M (Engelgard Institute of Molecular Biology, RAS, Moscow), Kompanets O N (ISAN, Troitsk, Moscow) “Structural nanotechnology of DNA (liquid-crystal approach) and its applications”; (5) Chekalin S V (ISAN, Troitsk, Moscow) “Femtosecond spectroscopy of promising materials”.Papers written on the basis of oral reports 1, 2, 4, and 5 are published below. • Near field phonon-polariton spectroscopy as a method for studying the optical properties of nanofilms, E A Vinogradov, N N Novikova, V A Yakovlev Physics-Uspekhi, 2014, Volume 57, Number 6, Pages 604–607 • Quantum control of atoms and photons by optical nanofibers, V I Balykin Physics-Uspekhi, 2014, Volume 57, Number 6, Pages 607–615 • Structural nucleic acid nanotechnology: liquid-crystalline approach, Yu M Yevdokimov, O N Kompanets Physics-Uspekhi, 2014, Volume 57, Number 6, Pages 615–621 • Femtosecond spectroscopy of promising materials, S V Chekalin Physics-Uspekhi, 2014, Volume 57, Number 6, Pages 622–629

Ultrahigh transmission optical nanofibers

We present a procedure for reproducibly fabricating ultrahigh transmission optical nanofibers (530 nm diameter and 84 mm stretch) with single-mode transmissions of 99.95 ± 0.02%, which represents a loss from tapering of 2.6 × 10−5 dB/mm when normalized to the entire stretch. When controllably launching the next family of higher-order modes on a fiber with 195 mm stretch, we achieve a transmission of 97.8 ± 2.8%, which has a loss from tapering of 5.0 × 10−4 dB/mm when normalized to the entire stretch. Our pulling and transfer procedures allow us to fabricate optical nanofibers that transmit more than 400 mW in high vacuum conditions. These results, published as parameters in our previous work, present an improvement of two orders of magnitude less loss for the fundamental mode and an increase in transmission of more than 300% for higher-order modes, when following the protocols detailed in this paper. We extract from the transmission during the pull, the only reported spectrogram of a fundamental mode launch that does not include excitation to asymmetric modes; in stark contrast to a pull in which our cleaning protocol is not followed. These results depend critically on the pre-pull cleanliness and when properly following our pulling protocols are in excellent agreement with simulations.

Quantum control of atoms and photons by optical nanofibers

Quantum control of atoms and photons by optical nanofibers

Tracing photon transmission in dye-doped DNA-CTMA optical nanofibers

We experimentally demonstrate the novel phenomena of photoluminescence (PL) and fluorescence resonance energy transfer (FRET) assisted three-color PL separating in DNA optical nanofibers consisting of the stretched and connected DNA-cetyltrimethyl ammonium wires. The PL experiments are performed to comparatively trace photon transmission between single dye-doped DNA-CTMA optical nanofiber and PMMA optical nanofiber. A cascade FRET including DNA minor groove binder and DNA intercalators is used to further trace photon transmission inside DNA-CTMA wire. These experimental results will help to intrigue the new applications of DNA-CTMA as molecular waveguide in optobioelectronics area.