The generation of a two-octave supercontinuum from the visible to mid-infrared (700-2800 nm) in a non-silica graded-index multimode fiber is reported. The fiber design is based on a nanostructured ...core comprised of two types of drawn lead-bismuth-gallate glass rods with different refractive indices. This yields an effective parabolic index profile and ten times increased nonlinearity when compared to silica fibers. Using femtosecond pulse pumping at wavelengths in both normal and anomalous dispersion regimes, a detailed study is carried out into the supercontinuum generating mechanisms and instabilities seeded by periodic self-imaging. Significantly, suitable injection conditions in the high power regime are found to result in the output beam profile showing clear signatures of beam self-cleaning from nonlinear mode mixing. Experimental observations are interpreted using spatio-temporal 3+1D numerical simulations of the generalized nonlinear Schrödinger equation, and simulated spectra are in excellent agreement with experiment over the full two-octave spectral bandwidth. Experimental comparison with the generation of supercontinuum in a silica graded-index multimode fiber shows that the enhanced nonlinear refractive index of the lead-bismuth-gallate fiber yields a spectrum with a significantly larger bandwidth. These results demonstrate a new pathway towards the generation of bright, ultrabroadband light sources in the mid-infrared.
In this paper we report a mid-infrared sensor based on an anti-resonant hollow core fiber. A quantum cascade laser operating around 4.53 µm is used to target one of the strongest transition of ...nitrous oxide near 2203.7 cm
. The system provides 1-second minimum detection limit at single parts-per-billion level using 3.2-m-long fiber with the response time of less than 30 seconds. Presented sensing approach shows a good perspective for compact and sensitive mid-infrared fiber-based spectrometers.
•A novel biosensor based on magnetic nanoparticles labeling and magneto-optical effect.•The harmonic response of AC magneto-optical dichroism can characterize concentration and particle size.•The ...design of liquid optic cavity can improve the sensitivity of measurement systems.•This detection method is rapid and low-cost, can be used to screen infected individual.
The technique investigates the application of the AC magneto-optical dichroism of magnetic fluids in fast and low-cost immunoassays by taking advantage of liquid optical cavities. Magnetic nanoparticles (MNPs) served as biomarkers. Variations in particle size were characterized by monitoring the amplitude of the second harmonic of transmitted light under alternating magnetic field excitation. Differential beams with polarization directions parallel and perpendicular to the magnetic field can improve signal-to-noise ratio. We designed a liquid optical cavity that allowed multiple reflections of light in magnetic fluid to increase the optical path. This cavity enhanced the magneto-optical signal and lowered the detection limits of target molecules. The limit of detecting biotin in the streptavidin–biotin binding system in conjunction with MNPs was 0.027 μg/mL and the least amount of time required for detection was 2.3 s. It is expected to achieve a low-cost, compact, and portable biosensor for rapid detection of trace viruses.
Hollow-core optical fibers have been used for laser gas sensing for almost two decades. However, to date, the vast majority of sensing systems have used hollow-core fiber only as a replacement for ...bulky gas cells (single- or multi-pass). Here, we investigate a reflective, dual-pass configuration in which light enters and exits hollow-core fiber from the same side. The advantage of this approach is the fact that the hollow-core fiber can be used not only as a cell but also as an endoscope-like probe, which does not need any additional tubing for sample delivery.
In this paper, we identify unwanted reflections from various fiber-to-fiber connections in the setup as the main challenge limiting the performance of the sensor in reflective configuration. We propose and experimentally demonstrate that the problem of reflections can be addressed using heterodyne-based detection, which allows for identifying and extracting useful signals in the radio frequency domain. Absorption and dispersion spectroscopy of methane are performed as a proof-of-concept with a detection limit of methane concentration below 10 ppm. Discussion insights into further development are provided, including strategies for miniaturization and detection limit improvement.
Experimental observation of mode-locked dissipative-soliton-resonance (DSR) pulses, including single-mode DSR pulses and multimode DSR pulses, in a Yb-doped fiber laser is reported. DSR pulses in ...single-mode state and multi-mode state can exist at the same time and can be output stably. The multi-mode DSR pulses exhibit same linearly broadening characteristics and bell-shaped spectral shape as single-mode DSR pulses. The results would be beneficial for expanding the knowledge of nonlinear dynamics to multimode fiber lasers and provide new insights for DSR pulse output with a fully multimode structure to get larger pulse energy.
•Stable output of DSR pulses in single-mode state and multi-mode state.•Characteristics of multi-mode DSR pulses in a Yb-doped fiber laser.•Comparison of single-mode DSR pulses and multi-mode DSR pulses at the same time.
For over a decade hollow-core fibers have been used in optical gas sensors in the role of gas cells. However, very few examples of actual real-life applications of those sensors have been ...demonstrated so far. In this paper, we present a highly-sensitive hollow-core fiber based methane sensor. Mid-infrared distributed feedback interband cascade laser operating near 3.27 µm is used to detect gas inside anti-resonant hollow-core fiber. R(3) line near 3057.71 cm
located in ν
band of methane is targeted. Compact, lens-free optical setup with an all-silica negative curvature hollow-core fiber as the gas cell is demonstrated. Using wavelength modulation spectroscopy and 7.5-m-long fiber the detection limit as low as 1.54 ppbv (at 20 s) is obtained. The demonstrated system is applied for a week-long continuous monitoring of ambient methane and water vapor in atmospheric air at ground level. Diurnal cycles in methane concentrations are observed, what proves the sensor's usability in environmental monitoring.
The nonlinear refractive index for 10 types of recently developed new soft glasses was measured under the same conditions using a pulsed Nd:YAG laser operating at 1064 nm with a 35 ps pulse duration. ...The study included various types of oxide-based soft glasses commonly used for nonlinear fiber optics, such as lead silicate, borosilicate, phosphatate, tellurite and heavy metal oxide glasses. All studied glasses have good rheological properties, and are suitable for further multi-step thermal processing, including fabrication of nonlinear photonic crystal fibers. As reference samples, standard fused silica glass and commercially available lead silicate glasses were used. The standard Z-scan setup was employed, with both “open-” and “closed-aperture” types of measurement. We show that nonlinearities of some benchmarked thermally stable heavy metal oxide glasses are comparable to more expensive and very fragile chalcogenide glasses.
We investigate the Verdet constant in selected heavy metal oxide glasses with good rheological properties for multiple thermal processing. The measurement results prove that lead-bismuth-gallate and ...tellurite glasses have Verdet constant of 69.33 rad T−1m−1 and 54.91 rad T−1m−1, respectively, at a wavelength of 475 nm. These magneto-optic responses are higher than in the case of pure silica or other commercially available soft glasses used in optical fiber development. The investigated glasses are potential candidates for all-fiber optical current sensors with enhanced sensitivity and resolution.
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•Verdet constant of heavy metal oxide glasses was determined•Investigated glasses are good candidate to build optical fiber current sensors•The dispersion of magnetooptic response is measured
The power scaling of single mode fiber lasers and amplifiers, due to the wide area of applications, has been the subject of great interest for many years. Increasing the mode area seems to be the ...obvious way to scale up the output power level from the single emitter if you consider well-known limitations like nonlinear effects, material damage threshold or thermal lensing. The nanostructurization of the fiber core is a method to control precisely optical properties of the active fiber. This method allows to design and develop the fiber with the core of any arbitrary defined refractive index distribution, with precision not available with other known fiber technology. The nanostructurization also open up an opportunity to incorporate simultaneously various active and non-active glasses into the fiber core. Those advantages can be used to fabricate the new class of fibers for laser applications. Here we show ytterbium doped phosphate single-mode fiber with nanostructured core, which is the first proof-of-concept of active fiber with entirely nanostructured core area.
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