Optical vortex beams, possessing spatial polarization or phase singularities, have intriguing properties such as the ability to yield super-resolved spots under focussing, and the ability to carry ...orbital angular momentum that can impart torque to objects. In this review, we discuss the means by which optical fibers, hitherto considered unsuitable for stably supporting optical vortices, may be used to generate and propagate such exotic beams. We discuss the multitude of applications in which a new class of fibers that stably supports vortices may be used, and review recent experiments and demonstration conducted with such fibers.
Internet data traffic capadty is rapidly reaching limits imposed by optical fiber nonlinear effects. Having almost exhausted available degrees of freedom to orthogonally multiplex data, the ...possibility is now being explored of using spatial modes of fibers to enhance data capadty. We demonstrate the viability of using the orbital angular momentum (OAM) of light to create orthogonal, spatially distinct streams of data-transmitting channels that are multiplexed in a single fiber. Over 1.1 kilometers of a specially designed optical fiber that minimizes mode coupling, we achieved 400-gigabits-per-second data transmission using four angular momentum modes at a single wavelength, and 1.6 terabits per second using two OAM modes over 10 wavelengths. These demonstrations suggest that OAM could provide an additional degree of freedom for data multiplexing in future fiber networks.
Optical rotation, a form of optical activity, is a phenomenon employed in various metrological applications and industries including chemical, food, and pharmaceutical. In naturally-occurring, as ...well as structured media, the integrated effect is, however, typically small. Here, we demonstrate that, by exploiting the inherent and stable spin-orbit interaction of orbital angular momentum fiber modes, giant, scalable optical activity can be obtained, and that we can use this effect to realize a new type of wavemeter by exploiting its optical rotary dispersion. The device we construct provides for an instantaneous wavelength-measurement technique with high resolving power R = 3.4 × 10
(i.e., resolution < 0.3 pm at 1-μm wavelengths) and can also detect spectral bandwidths of known lineshapes with high sensitivity.
With growing interest in the spatial dimension of light, multimode fibers, which support eigenmodes with unique spatial and polarization attributes, have experienced resurgent attention. Exploiting ...this spatial diversity often requires robust modes during propagation, which, in realistic fibers, experience perturbations such as bends and path redirections. By isolating the effects of different perturbations an optical fiber experiences, we study the fundamental characteristics that distinguish the propagation stability of different spatial modes. Fiber perturbations can be cast in terms of the angular momentum they impart on light. Hence, the angular momentum content of eigenmodes (including their polarization states) plays a crucial role in how different modes are affected by fiber perturbations. We show that, accounting for common fiber-deployment conditions, including the more subtle effect of light’s path memory arising from geometric Pancharatnam–Berry phases, circularly polarized orbital angular momentum modes are the most stable eigenbasis for light propagation in suitably designed fibers. Aided by this stability, we show a controllable, wavelength-agnostic means of tailoring light’s phase due to its geometric phase arising from path memory effects. We expect that these findings will help inform the optimal modal basis to use in the variety of applications that envisage using higher-order modes of optical fibers.
Vortex fibers for STED microscopy Yan, Lu; Kristensen, Poul; Ramachandran, Siddharth
APL photonics,
02/2019, Letnik:
4, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Super-resolution imaging using the principles of stimulated emission depletion (STED) microscopy requires collinear excitation of a sample with a Gaussian-shaped excitation beam and a donut-shaped ...depletion beam whose spin (polarization) and orbital angular momentum (OAM) signs are aligned. We leverage recent advances in stable OAM mode propagation in optical fibers for telecom applications to design, fabricate, and validate the utility of a vortex fiber as the beam shaping device at visible and near-IR wavelengths for STED microscopy. Specifically, using compact UV-written fiber-gratings yielding high purity mode conversion (98.7%), we demonstrate the simultaneous generation of Gaussian and OAM beams at user-defined wavelengths. Point spread function measurements reveal a depletion beam with >17.5-dB extinction ratio, a naturally co-aligned Gaussian beam, and a setup in which these characteristics are maintained even as the fiber is bent down 6-mm radii. The proof-of-concept of all-fiber STED microscopy realized using this fiber device is used to image fluorescent bead samples yielding a sub-diffraction-limited resolution of 103 nm in the lateral plane. This opens the door to performing fiber-based STED microscopy with a setup that is not only resistant to environmental perturbations but also facilitates the development of endoscopic STED imaging.
Single-pixel cameras reconstruct images from a stream of spatial projection measurements recorded with a single-element detector, which itself has no spatial resolution. This enables the creation of ...imaging systems that can take advantage of the ultra-fast response times of single-element detectors. Here we present a single-pixel camera with a temporal resolution of 200 ps in the visible and short-wave infrared wavelengths, used here to study the transit time of distinct spatial modes transmitted through few-mode and orbital angular momentum mode conserving optical fiber. Our technique represents a way to study the spatial and temporal characteristics of light propagation in multimode optical fibers, which may find use in optical fiber design and communications.
Methicillin-resistance among Staphylococcus species is a major health problem in hospitals, communities, and animals. There is a need for culture-free diagnostic assays that can be carried out ...rapidly, and maintain a high degree of sensitivity and specificity. To address this need an ionic self-assembled multilayer (ISAM) film was deposited on the surface of a long-period grating (LPG) optical fiber by immersion alternately in poly-allylamine hydrochloride and in poly-1-p-(3′-carboxy-4′-hydroxyphenylazo) benzenesulfonamido-1,2-ethandiyl (PCBS), resulting in terminal carboxyl groups on the LPG-ISAM. The terminal carboxyl groups were covalently conjugated to monoclonal antibodies (MAb) specific to penicillin-binding-protein 2a of methicillin resistant (MR) staphylococci. After exposure of the LPG-ISAM to 102 colony forming units (CFU)/ml of MR S. aureus (MRSA) for 50min., light transmission was reduced by 19.7%. In contrast, after exposure to 106CFU/ml of methicillin-sensitive S. aureus (MSSA) attenuation of light transmission was less than 1.8%. Exposure of the LPG-ISAM to extracts of liver, lungs, or spleen from mice infected with MRSA attenuated light transmission by 11.7–73.5%. In contrast, exposure of the biosensor to extracts from MSSA-infected mice resulted in 5.6% or less attenuation of light transmission. When the sensor was tested with 36 strains of MR staphylococci, 15 strains of methicillin-sensitive staphylococci, 10 strains of heterologous genera (all at 104CFU/ml), or tissue samples from mice infected with MRSA, there was complete agreement between MR and non-MR bacteria determined by antibiotic susceptibility testing and the biosensor assay when the cutoff value for attenuation of light transmission was 6.3%. Thus, the biosensor described has the potential to detect MR staphylococci in clinical samples with a high degree of sensitivity and specificity.
•We developed an optical biosensor to detect methicillin-resistant staphylococci (MRS).•MRS were detected in 1h by attenuation of light transmission through the fiber.•As few as 100 MRS could be detected, but not 1 million methicillin sensitive bacteria.•MRS in swabs of tissues from infected mice were readily detected.•The optical biosensor has potential in diagnostic applications for infectious agents.
Shaping the transverse spatial domain of light has been experiencing recent growth in attention for its applications in optical tweezing, microscopy, communications, and quantum information sciences. ...The orbital angular momentum (OAM) of light is a transverse physical property that functions as a viable basis for many of such applications. While fields containing a single OAM mode order have extensively been used, fields containing a broad, discrete, and equally spaced OAM spectrum—an OAM comb—has largely been unexplored due to a lack of viable creation methods. Much like how frequency combs enabled myriad applications, it is conceivable that OAM combs would likewise enable further opportunities or expand upon single-OAM applications. For instance, an OAM comb may pave the way for more sophisticated particle manipulation, object detection, and pump shaping for high-dimensional spatial-mode entanglement. Here, we create four OAM combs with rectangular, sinusoidal, sinc, and Gaussian OAM spectral distributions using multiplane light conversion, which only involves phase modulations (hence is inherently lossless) and allows for improved tailoring of the spatial shape. The verification of such combs is done qualitatively by analyzing their propagation evolutions and quantitatively by employing a mode sorting technique—both exhibiting good agreement with user specifications and simulations. The scattering losses of all four combs were measured to be minimal, ranging from 0.66 to 1.04 dB.
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