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Highly resolved distributed monitoring of strain and temperature can be easily achieved by means of fiber-optic Brillouin-based sensors. The majority of available Brillouin systems relies on Brillouin Optical Time Domain Analysis (BOTDA) techniques in which pulsed pump and/or signal waves are exploited, allowing a spatial resolution fundamentally restricted to about 1 meter [1]. Brillouin Optical...
We present, for the first time, the results regarding the production of refractive index (RI) sensors, through the acousto-optic effect in tilted fiber Bragg gratings (TFBGs). The RI is analysed in detail when acoustic waves are turned on using saccharose solutions with different RI from 1.3327 to 1.4249.
High-throughput fully distributed fiber Bragg grating (FBG) sensors based on optical time-stretch frequency-domain reflectometry (OTS-FDR) [1] has proved to be a promising tool for high temporal and spatial resolution distributed strain sensing. The dynamic distributed strain information along the FBG sensor can be reconstructed from the instantaneous RF frequency of the captured temporal interference...
In the last few years, several authors have reported the observation of a new class of acoustic waves in sub-wavelength diameter tapered optical fibers (TOFs) through Brillouin scattering [1, 2]. These include the observation of surface acoustic waves (SAW), hybrid shear and longitudinal acoustic waves (HAW) associated with anti-crossings (AC). It has also been suggested that these acoustic waves...
When an optical fibre crosses a magnetic field, a Faraday effect is generated, which perturbs the optical propagation, causing a modulation of the state of polarization (SOP) of the optical signal along the fibre [1]. This well known effect is often used to develop optical fibre current sensors. Yet, in optical communications systems relying on polarization sensitive elements (e.g. coherent detectors,...
We report our advances in development of subwavelength engineered metamaterial structures in silicon waveguides, specifically high-efficiency fiber-chip couplers, ultra-broadband surface grating couplers and nanophotonic beam splitters, evanescent field waveguide sensors and on-chip Fourier-transform spectrometers.
Optical sensing techniques are considered as one of the most advancing and extensively investigated fields of photonics technologies. The fundamental advantages of optical sensors such as immunity to electro-magnetic interference, compact size and energy efficiency designate them to use in highly requiring applications, e.g. in harsh environment and aviation. Modern optical gyroscope systems, which...
Integrated Optical Fibre (IOF) is a passive optical platform that directly integrates optical fibre to a planar substrate, illustrated in Fig 1(a). It possess advantages associated with optical fibre such a low propagation loss, whilst enabling planar functionality commonplace with integrated optics. Planarization is uniquely achieved through a modified Flame Hydrolysis Deposition (FHD) technique...
We demonstrate miniaturized micro- and nano-optics. Our approach uses femtosecond 3D direct laser writing. Aberration-corrected performance for large angles of incidence is achieved, and our approach solves the common problem of off-axis coma in metasurfaces.
In recent years, all-solid photonic bandgap fibers (AS-PBFs) have attracted great attentions since they can be applied to many devices such as tunable filters, optical modulators, fiber lasers, amplifiers and sensors [1]. The AS-PBF is related to an optical fiber whose cladding consists of an arrangement of isolated high-index rods in a low-index background [2]. The fiber core of an AS-PBF locates...
At the Naval Research Laboratory (NRL), we are developing infrared glasses, ceramics and optical fibers for many active and passive applications. The chalcogenide glasses transmit from approximately 1 μm to 12 μm in the important infrared wavelength region. Fibers have been developed for passive applications, including light-pipes for remote chemical sensor systems for environmental pollution monitoring,...
The use of thermally regenerated gratings for monitoring harsh environments is becoming increasingly attractive due to their thermal resilience and high precision. They are a unique type of Bragg grating created through annealing UV-laser written Fiber Bragg Gratings (FBGs) at high temperatures (above 600°C) and they have been demonstrated to operate at temperatures over 1000 °C in oxygen free environments...
Harsh environmental sensing using fiber Bragg grating (FBG) technologies is a rapidly growing field of research. A new generation of devices that operate in extreme environments (particularly those operating above 800°C) including environments with additional challenges such as radiation and intense optical fields (e.g. high power lasers), must be capable of withstanding gradual annealing and degradation,...
Fiber lasers are sources where the active medium is an optical fiber with core doped by active ions such as Nd (neodymium), Yb (ytterbium), Er (erbium), Tm (thulium) [1] and their main utilizations in medicine are related to the lithotripsy [2], the surgical treatment of vascular lesions [3], the non-surgical skin aesthetic procedures [4, 5], the urinary surgery [6] and the eye surgery [7].
The work introduces textile based carbon structures that are functionalized with optical fibre sensors for structural health monitoring (SHM) of concrete based composites. The concept of the functionalized carbon reinforcement structure is shown in Fig. 1a. The optical fibre (that contains the sensors) is integrated directly during the manufacturing of the carbon reinforcement structure. Due to the...
Intense ultrafast laser sources in the mid-IR have attracted in the recent years lot of attention in strong-field physics. A possible implementation for such sources relies in: a) the generation of a short IR seed by intra-pulse difference frequency generation (DFG) of a broadband continuum generated in an hollow-core fiber (HCF); b) optical parametric amplification (OPA) of the seed to the mJ level...
Fiber Bragg gratings (FBGs) are well-known to be essential elements in optical communications, optical fiber based sensors and fiber lasers [1]. One of the most recent methods for fabricating FBGs is referred to as point-by-point inscription and uses femtosecond duration pulses of an infrared laser tightly focused to the fiber core region, such that every pulse forms a single grating period [2]. The...
Recent progresses in hollow-core photonic crystal fibers (HC-PCF) renewed interest for resonant fiber optic gyroscope (R-FOG) [1]. Indeed, hollow-core fibers, where light propagates mostly in air, have the advantage of significantly reducing the Kerr effect, known as a strong limitation on the bias stability of the R-FOG [2]. However, Rayleigh backscattering is still an important source of noise as...
Non-intrusive electric field sensing devices have recently attracted attention due to their capability to face the problem derived from the conventional sensing probes which present a large sensing area and are based on conductive materials, distorting the field to be measured. This constraint is solved by employing all optical and compact probes which rely on electro-optical materials. However, all...
Driven by demands from medicine and the life sciences, for example, a variety of new point of care tests (POCT) based on smartphones are currently investigated [e.g. 1]. For instance, in combination with an external electrical read out system smartphones have been applied for the monitoring of diabetes or, by employing the smartphone camera, for the interrogation of lateral flow tests.
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