In this study, we present a fiber-tip Fabry-Perot interferometer operating in reflective mode, fabricated on the end faces of standard single-mode optical fibers using the Two-Photon Polymerization 3D nanoprinting method. Theoretical analysis highlights the primary challenge in accurately fitting the geometric dimensions of the cavity due to light beam divergence at the end of a single-mode fiber. Therefore, significant emphasis was placed on creating a compact structure with a high-reflection mirror formed on the printed tip. Various shapes of reflective surfaces were tested, including flat and concave. Additionally, to improve reflection we used the cathode sputtering method to get thin metal films on the printed surfaces. During conducted research, it has been demonstrated that the optimal solution is to cover only one surface of the resonator. This necessitated the development of a structure with a unique shape, enabling the deposition of a thin metallic layer solely on the top surface while simultaneously preventing deposition on the core.
In this study, experimental investigation of fiber-based Fabry-Perot is compared against the theoretical predictions of Fabry-Perot resonators. The special emphasis in this study was placed on testing the perspectives for resonance enhancement by coating the fiber facets by highly reflective surfaces and by replacing the flat surfaces by concave mirrors fabricated by the Two-Photon Polymerization (2PP) 3D nano-printing method. Golden layers of varying thickness were deposited on both flat and concave mirrors of optical fiber Fabry-Perot resonators, which were constructed from simply two optical fiber tips carefully aligned parallel to each other. An improvement of extinction ratio by even 12.5 dB and higher finesse of the resonance signal was registered. The resonance spectra resulting from such modifications were measured and discussed in relation to the assumptions of the theory for free-space Fabry-Perot resonators. It was demonstrated that the most optimal reflectance (R) values of both mirrors for the standard Fabry-Perot cavities (R1 = R2) are not the most optimal in case of fiber Fabry-Perot cavities.
This study presents the influence of temperature and electric field on optical power spectrum of an optical fiber taper device coated with nematic liquid crystal. The fiber-optic device consists tapered fiber placed between two glass electrodes covered with alignment layer and ITO. The tapering process caused the elongation of the optical fiber equal to 20.20 ± 0.16 mm and the taper waist diameter equal to 12 ± 0.5 μm. The applied tapered fiber is characterized by losses lower than 0.5 dB in the whole investigated spectrum range. The device was filled with nematic liquid crystal mixture E7 which is designed for an electric as well as temperature control of electromagnetic wave propagation. The measurements were performed for three kinds of initial liquid crystal molecules’ orientation (parallel, orthogonal and twist) in relation to the light beam propagating in the taper as well as axis of fiber. The induced reorientation of liquid crystal molecules was measured for visible and near infrared wavelength range [500-900 nm] at electric field range of 0–160 V and the temperature range of 20-60 °C. The relation between temperature and optical power spectrum of investigated fibers has been established.
Presented article shows the effect of using ZnS:Mn nanoparticles in the solution of higher alkanes on the light wave propagation in a biconical, adiabatic optical fiber taper. The used mixture of alkanes with nanoparticles forms a special cladding surrounding a fiber taper. Described studies show change of beam intensity depending on mixture temperature and its state of aggregation. Tests were carried out in a wide spectral range from the visible up to infrared wavelengths. The taper was made of a standard single-mode telecom fiber, pulled out to a length of 20.0 ± 0.5 mm and the diameter of the taper waist is 14.0 ± 0.2 μm. Such taper causes the beam to leak out of a waist structure and allows to add an external beam-controlling cladding material. The built-in sensor containing nanoparticles operates on the on-off principle. Nanoparticles added to the alkanes cause increase of hysteresis in a heating and cooling process. Such mixture makes also a significant shift of temperature characteristic in a heating process in which mixture change their physical state with a simultaneous slight shifting of the characteristics during cooling. Depending on the source used, weakening or amplification of the signal was obtained after switching to the liquid state.
Tapering technique is one of the most useful in the telecommunications as well as in sensing which offers up to now the best quality fused optical fiber elements such as couplers, splitters and combiners. It allows to fabricate various types of the tapers used as platforms of optical fiber transducers for chemical or biological sensors, as well. In the paper polarization properties of an optical biconical taper with liquid crystal cladding are presented. The optical fiber taper manufactured by mentioned above technique was sandwiched between parallel glass plates with ITO and alignment layers to form a tested optical element. Standard nematic liquid crystals E7 and 6CHBT were applied as claddings of the tapered fiber. Sufficient transmission losses of infrared radiation were observed when orientation layers of glass plates were perpendicular to the tapered fiber. The main contribution of this paper is calculation the polarization properties of the tested samples by the Lu-Chipman decomposition method based on measured Mueller matrices. Analysis of measurements show that the applied voltages have the strongest influence on transmission losses and dichroism. These effects will be carefully investigated towards the voltage sensor and emulators of polarization depended loss.
The paper presents the results of manufacturing and characterization of a broad band in-line hybrid device using a nematic liquid crystal as an active cladding for biconical tapered optical fiber. Two different liquid crystal mixtures denoted as 1550* and E7 were used for electric and temperature control in a broad wavelength range. An optical fiber tapers with a waist of 10±0.5 μm and losses lower than 0.5 dB in a whole broad band spectrum range were applied. Such taper waist diameter makes the whole waist as core for light propagation, where the surrounding air becomes the cladding. Additionally, such diameter enables an effective control of molecules orientation. Performance of a tuned cladding was studied in an electric field in the range between 0 V and 160 V in the room temperature equal to 20 °C. Influence of induced liquid crystal molecules reorientation was measured at a broad wavelength range (500-1700 nm).
The paper presents the results of design, manufacturing and characterization of an hybrid broad band in-line device using a nematic liquid crystal as an active medium which influences light propagating in a biconical optical fibre taper. A liquid crystal mixture denoted 6CHBT*and E7 is designed for electric, as well as temperature control of electromagnetic wave propagation in a broad wavelength range. The main reason of using the taper structure with a waist of 10± 0.5 μm and losses lower than 0.5 dB is possibility of using a liquid crystalline medium as cladding. Such approach enables effective control of its refractive index. Two kinds of initial liquid crustal molecules’ orientation (parallel and orthogonal) in relation to the light beam propagating in a taper were applied. Performance of a tuned cladding was studied at electric field of the range of 0V – 160V in the room temperature equal to 20°C. Influence of induced reorientation of liquid crystal molecules was measured at a broad wavelength range [500-1700 nm].
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