Multimode optical fibers have seen increasing applications in communication, imaging, high-power lasers, and amplifiers. However, inherent imperfections and environmental perturbations cause random ...polarization and mode mixing, causing the output polarization states to be different from the input polarization states. This difference poses a serious issue for employing polarization-sensitive techniques to control light-matter interactions or nonlinear optical processes at the distal end of a fiber probe. Here, we demonstrate complete control of polarization states for all output channels by only manipulating the spatial wavefront of a laser beam into the fiber. Arbitrary polarization states for individual output channels are generated by wavefront shaping without constraining the input polarization. The strong coupling between the spatial and polarization degrees of freedom in a multimode fiber enables full polarization control with the spatial degrees of freedom alone; thus, wavefront shaping can transform a multimode fiber into a highly efficient reconfigurable matrix of waveplates for imaging and communication applications.
In general, a sensor is used to monitor a single parameter only, and in many cases, a reference sensor is necessary to compensate the effect of temperature. Here, we demonstrate that a single ...supermode interferometer is capable of monitoring two parameters simultaneously. Said interferometer was fabricated with a segment of strongly coupled multicore fiber fusion spliced at the end of a standard single mode fiber. The free end of the multicore fiber was flat, thus, it behaved as a low reflectivity mirror whose reflection depended on the external refractive index. The reflection spectrum of our supermode interferometer consisted of well-defined periodic maxima and minima whose values and position varied when the interferometer was exposed to refractive index and temperature changes. In the Fourier domain, the changes of the interference pattern can be decoded easily. We demonstrate that the supermode interferometer here proposed can be useful to measure the thermo-optic coefficient of a sample. An important advantage of the device reported here is that the length of the multicore fiber is not determinant on the performance of the sensor. In addition, the device can be reused multiple times.
Light Transmission Through a Hollow Core Fiber Bundle Sufian, Md Abu; Baleine, Erwan; Geldmeier, Jeffrey ...
IEEE journal of selected topics in quantum electronics,
01/2024, Volume:
30, Issue:
6: Advances and Applications of Hollow-Core Fibers
Journal Article
Peer reviewed
Open access
This paper reports on the fabrication and performance of a fiber bundle with seven hollow cores arranged in a hexagonal pattern. The bundle shows individual core transmission with less than 0.07% ...core-to-core coupling over a length of 11 cm. Each core exhibits several transmission windows in the visible to near infrared region. These low attenuation regions with large higher order mode suppression are a result of anti-resonant guidance due to the negative curvature membranes encircling the cores. The central core exhibits the widest transmission window with a minimum loss of 4 dB/m between 1250 nm and 1450 nm. The lowest loss for the central core is estimated to be 2.5 dB/m at 600 nm. Such hollow core fiber bundles may be employed in applications including communication, imaging systems, high power laser delivery, or sensing.
In this paper, we numerically investigate various hollow-core anti-resonant (HC-AR) fibers towards low propagation and bend loss with effectively single-mode operation in the telecommunications ...window. We demonstrate how the propagation loss and higher-order mode modal contents are strongly influenced by the geometrical structure and the number of the anti-resonant cladding tubes. We found that 5-tube nested HC-AR fiber has a wider anti-resonant band, lower loss, and larger higher-order mode extinction ratio than designs with 6 or more anti-resonant tubes. A loss ratio between the higher-order modes and fundamental mode, as high as 12,000, is obtained in a 5-tube nested HC-AR fiber. To the best of our knowledge, this is the largest higher-order mode extinction ratio demonstrated in a hollow-core fiber at 1.55 μm. In addition, we propose a modified 5-tube nested HC-AR fiber, with propagation loss below 1 dB/km from 1330 to 1660 nm. This fiber also has a small bend loss of ~15 dB/km for a bend radius of 1 cm.
Few-mode lensed fiber for focusing multiple spatial modes with minimal distortion are proposed and investigated numerically and experimentally, for the first time to the best of the authors' ...knowledge. Although the conventional hyperbolic lens profile works effectively for the fundamental mode, it introduces severe distortion for high-order radial modes. This distortion is due to destructive interference between out-of-phase lobes in the radial direction. To reduce this distortion, we modify the lens profile to avoid such destructive interference. Focused images with significantly reduced distortions were observed in our experiments.
Recognizing objects directly from optical fiber output images is useful in endoscopic applications when forming a clear image of the object is unnecessary or rather difficult. Conventional ...fiber-optic systems, such as multicore-fiber-based and multimode-fiber-based systems, suffer from the sensitivity of the fiber to external perturbations. For example, a slight movement of the fiber (a-few-millimeters translation of the tip for meter-long multicore fibers or multimode fibers) can greatly change the output images of the system. In this work, we utilize the light guidance stability of recently proposed glass-air Anderson localizing optical fiber (GALOF) to achieve robust imaging-free objection recognition. We transport five classes of cell images through an 80-cm straight GALOF. A deep convolutional neural network is trained to classify the output images and tested on images never seen, namely, images collected when the fiber is bent or when the fiber facet is placed several millimeters away from the object without any distal optics. Bending-invariant high classification accuracy (86.8% on average) is observed all the way to the maximum bending offset distance of 45 cm (∼74thinsp;° bending angle). High classification accuracy (91.2%) is also preserved when the fiber facet is 0.5 mm away from the object.
We present a randomly disordered silica-air optical fiber featuring a 28.5% air filling fraction in the structured region, and low attenuation below 1 dB per meter at visible wavelengths. The quality ...of images transported through this fiber is shown to be comparable to, or even better than, that of images sent through commercial multicore imaging fiber. We demonstrate robust high-quality optical image transfer through 90 cm-long fibers with disordered silica-air structure, more than an order of magnitude improvement compared to previous disordered fiber imaging distances. The effects of variations of wavelength and feature size on transported image quality are investigated experimentally.
We used a single-shot ptychographic microscope to image the complex-valued (intensity and phase) spatial profiles of multiple ultrashort pulses. Specifically, we present a characterization of a burst ...of three ultrashort pulses with three nanoseconds delays between pulses using data recorded by a single camera exposure with millisecond integration time. This scheme is promising for various applications, including characterizing spatiotemporal mode-locked or Q-switched lasers, potentially shedding light on their buildup dynamics.
Recent years have witnessed the tremendous development of fusing fiber-optic imaging with supervised deep learning to enable high-quality imaging of hard-to-reach areas. Nevertheless, the supervised ...deep learning method imposes strict constraints on fiber-optic imaging systems, where the input objects and the fiber outputs have to be collected in pairs. To unleash the full potential of fiber-optic imaging, unsupervised image reconstruction is in demand. Unfortunately, neither optical fiber bundles nor multimode fibers can achieve a point-to-point transmission of the object with a high sampling density, as is a prerequisite for unsupervised image reconstruction. The recently proposed disordered fibers offer a new solution based on the transverse Anderson localization. Here, we demonstrate unsupervised full-color imaging with a cellular resolution through a meter-long disordered fiber in both transmission and reflection modes. The unsupervised image reconstruction consists of two stages. In the first stage, we perform a pixel-wise standardization on the fiber outputs using the statistics of the objects. In the second stage, we recover the fine details of the reconstructions through a generative adversarial network. Unsupervised image reconstruction does not need paired images, enabling a much more flexible calibration under various conditions. Our new solution achieves full-color high-fidelity cell imaging within a working distance of at least 4 mm by only collecting the fiber outputs after an initial calibration. High imaging robustness is also demonstrated when the disordered fiber is bent with a central angle of 60°. Moreover, the cross-domain generality on unseen objects is shown to be enhanced with a diversified object set.
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