Performance of Extrinsic Fabry–Perot Interferometer Based on Graded-Index Lenses for a Fabry–Perot Cavity with Surface Errors

Interference contrast is an important parameter for extrinsic Fabry–Perot interferometer (EFPI) based on graded index (GRIN) lenses. It determines the signal-to-noise ratio (SNR) and the measurement accuracy. We discuss the influence of Fabry–Perot (FP) cavity surface errors, which are inevitable in controlling the interference contrast during the manufacturing procedure. Our theoretical analysis and results of numerical simulations demonstrate that the surface errors diminish the interference contrast — the larger the surface error, the smaller the interference contrast. The results obtained contribute to the EFPI application in fiber sensors.     

Express Analysis of Gas Mixtures Using a Spectral Correlator Based on the Fabry–Perot Interferometer

Journal of Applied Spectroscopy - Optical correlation methods for the analysis of gas mixtures with a quasi-periodic spectrum structure are described. The design of a device for demonstrating the...     

Four‐Wave Mixing in a Nonlinear Fabry–Perot Interferometer

A theoretical model of fourwave mixing in a Fabry–Perot interferometer with resonant nonlinearity has been developed. The conditions for the realization of the effect of interferometer transmission symmetry breaking and the specific features of the formation of spacetime structures of light fields have been analyzed. The laws of hysteresis of the lateral laser beam profiles have been established.     

An Extrinsic Fabry–Perot Optical Fiber Sensor Based on Nano-Magnetic Fluid

Abstract

An extrinsic Fabry–Perot optical fiber sensor based on nano-magnetic fluid and a Fabry–Perot interference is presented for magnetic field measurement. The sensing fiber end is coated with a thin film of SU-8 photoresist; immersing it into a nano-magnetic fluid forms a magnetic-field-dependent extrinsic Fabry–Perot interference. The relationship between the fringe contrast and magnetic field is analyzed in different concentrations of the magnetic fluid, and the concentration of 25% is most suitable for the measurement of the magnetic field intensity. The stability of the sensor is also addressed.     

Estimation of the Dispersion of Absorptance in the Region of Resonant Transitions Using the Reflection Spectra in a Fabry–Perot Interferometer

It is shown that in the region of resonant transitions the dependence of the area under the contour of the Fabry–Perot interference bands on the frequency minus the area under the envelope of the minima reflects the character of the dispersion of light absorptance.     

A high-finesse fiber optic Fabry–Perot interferometer based magnetic-field sensor

A high-finesse extrinsic Fabry–Perot interferometric sensor for the measurement of weak dc magnetic fields is demonstrated. The Fabry–Perot cavity is formed by aligning the fiber end-face and the TbDyFe rod end-face, and each end-face is coated by a mirror with a micro-lens. The length of the TbDyFe rod is changed by the variation of an applied dc magnetic field, leading a change of the Fabry–Perot cavity length. By interrogating the white-light interferometric spectrum, the wavelength of the resonant peak is tracked and the length of the Fabry–Perot cavity is obtained. The sensor exhibits a high sensitivity of 1510 nm/mT with a magnetic resolution of 25 nT.     

A thin wire ion trap to study ion–atom collisions built within a Fabry–Perot cavity

We report on the implementation of a thin wire Paul trap with tungsten wire electrodes for trapping ions. The ion trap geometry, though compact, allows large optical access enabling a moderate finesse Fabry–Perot cavity to be built along the ion trap axis. The design allows a vapor-loaded magneto-optical trap of alkali atoms to be overlapped with trapped atomic or molecular ions. The construction and design of the trap are discussed, and its operating parameters are determined, both experimentally and numerically, for Rb⁺. The macromotion frequencies of the ion trap for ⁸⁵Rb⁺ are determined to be f _r  = 43 kHz for the radial and f _z  = 54 kHz for the axial frequencies, for the experimentally determined optimal operating parameters. The destructive off axis ion extraction and detection by ion counting is demonstrated. Finally, evidence for the stabilization and cooling of trapped ions, due to ion–atom interactions, is presented by studying the ion-atom mixture as a function of interaction time. The utility and flexibility of the whole apparatus, for a variety of atomic physics experiments, are discussed in conclusion.     

Extension of the classical Fabry–Perot formula to 1D multilayered structures

In any field theory the interaction of a wave packet with a multilayered potential is of high theoretical and practical relevance. In the present work we show an extension to any number of layers of the classical Fabry–Perot formula that works for any level of absorption, any thickness of the composing layers, any number of layers, any angle of incidence and for evanescent waves as well. More specifically, the ability of dealing with input evanescent waves and complex metal-based structures is of special interest for superlenses analysis and design. Some explicit examples in electromagnetism are also discussed.     

Large-range liquid level sensor based on an optical fibre extrinsic Fabry–Perot interferometer

We propose an efficient approach to develop large-range liquid level sensors based on an extrinsic Fabry–Perot optical fibre interferometer with an all fused-silica structure and CO₂ laser heating fusion bonding technology. The sensor exhibits signatures of a high sensitivity of 5.3 nm/kPa (36.6 nm/psi), a resolution of 6.8 Pa (9.9×10⁻⁴ psi) and an extreme low temperature dependence of 0.013 nm/°C. As a result, a high resolution of the water level measurement of approximately 0.7 mm on the length scale of 5 m and small errors of the water pressure measurement induced by the temperature dependence within 0.0025 kPa/°C (0.00036 psi/°C, water level 0.25 mm/°C) are achieved, thus providing useful applications for the detection of the large-range liquid level in harsh environments.     

Mechanism investigation of a narrow-band super absorber using an asymmetric Fabry–Perot cavity

We propose a metal–insulator-metal super absorber based on an asymmetric Fabry–Perot cavity, by which a perfect narrow-band absorption can be achieved. In this structure, two silver layers form a cavity spaced by a lossless silicon oxide layer. The absorption of the absorber can reach about 98% and its absorption peak can be tuned by altering the thickness of the middle SiO₂ layer. We further present a deep comprehension on the physics mechanism of such high absorption. This super absorber can be easily fabricated by mature thin film technology, which make it an appropriate candidate for photodetectors, sensing, and spectroscopy.     

A review of visible-range Fabry–Perot microspectrometers in silicon for the industry

This review presents microspectrometers in silicon for the industry for measuring light in the visible range, using the Fabry–Perot interferometric technique. The microspectrometers are devices able to do the analysis of the individual spectral components in a given signal and are extensively used on spectroscopy. The analysis of the interaction between the matter and the radiated energy can found huge applications in the industrial sector. The microspectrometers can be divided on three types, determined by the dispersion element or the used approach and can be found microspectrometers based on prisms, gratings interferometers. Both types of microspectrometers can be used to analyze the spectral content ranging from the ultraviolet (UV, below 390 nm), passing into the visible region of the electromagnetic spectrum (VIS, 390–760 nm) up to the infrared (IR, above 760 nm). The microspectrometers in silicon are versatile microinstruments because silicon-compatible techniques can be used to assembly both the optical components with the readout and control electronics, thus resulting high-volume with high-reproducibility and low-cost batch fabrications. A compensation technique for minimizing the scattered light effects on interferometers was implemented and is also a contribution of this paper. Fabry–Perot microspectrometers for the visible range are discussed in depth for use in industrial applications.     

A Novel Mach–Zehnder Interferometer Based on Hybrid Liquid Crystal–Photonic Crystal Fiber

We propose a novel all fiber Mach–Zehnder interferometer(MZI) based on photonic crystal fiber(PCF) filled with liquid crystal(LC). The interference between the core mode and the cladding modes of a PCF is utilized.To excite the cladding modes, a region is formed using fiber fusion splicer. Due to the fact that varying effective index difference between the core region and the LC-filled cladding region can cause different transmission spectra,we mainly study the MZIs with different LC-filled structures and different lengths of LC filling. The measured results demonstrate that quite clear interference spectra can be obtained. Through analysis spatial frequency spectrum and temperature spectrum of two MZIs with different LC-filled structures, we can obtain that the MZI with adjacent two LC-filled holes has clearer interference spectrum and higher temperature sensitivity. Thus we choose this MZI to measure the temperature sensitivity with different lengths of LC filling. When the length of LC filling is 2 cm, the temperature sensitivities can be enlarged to 1.59 nm/C. The interferometer shows a good temperature tunability and sensitivity, which can be a good candidate for a highly tunable optical filtering and temperature sensing applications.     

A Novel Technique to Measure the Spatial–Temporal Intensity of an Ultrashort Pulse

Based on a modified cross-correlation technique, we experimentally demonstrate a technique for measuring the spatial–temporal intensity of laser pulses. Pulse widths at different spatial positions of the ultrashort pulse are measured by changing the scan position of the probe beam. Due to the existence of residual chirp in the transverse position, pulse widths at the center of the beam are less than that at the edge. By measuring the temporal evolution in the fastest growth area of spatial intensity during small-scale self-focusing, we find that its pulse width decreases as power increases because of the spatial–temporal coupling effect. The results show that this method not only can be used to accurately measure the pulse width at any one spatial position of the beam, but can also be useful for real-time monitoring of the spatial–temporal evolution.     

A narrow-linewidth continuous wave Ho:YALO3 laser with Fabry–Perot etalons

A narrow linewidth continuous wave Ho:YAP laser with two Fabry–Perot etalons pumped by a Tm:YLF laser is reported. The maximum output power reaches 8.3 W when the incident pump power is 15.8 W, with 52.5% optical-tooptical conversion efficiency and 62.6% slope efficiency. A stable laser output at 2118.1 nm is achieved, with a linewidth less than 0.4 nm(full width at half maximum). The beam quality factor is M2～ 1.25, measured by the traveling knife-edge method.     

A Novel Optical Filter for Removing Bright-Background Using an Enhanced Bacteriorhodopsin Thin Film

We found that the bacteriorhodopsin (bR) film has a special property of complementary suppression modulated transmission (CSMT). The yellow and the blue beams can be suppressed mutually when both the beams illumlnate the bR film simultaneously. When the blue beam carrying an image with a bright-background noise illuminates on the bR film and then a yellow beam with uniform intensity distribution illuminates the same area, the bright-background can be removed due to the CSMT. In our demonstration, the pattern model is letters “VLSF” with ground noise of small words and the ground noise is removed from the pattern by the new optical filter.     

Temperature-insensitive refractive index sensor based on an optical fiber extrinsic Fabry–Perot interferometer processed by a femtosecond laser

An optical fiber extrinsic Fabry–Perot interferometer(EFPI) is designed and fabricated for refractive index(RI)sensing.To test the RI of liquid,the following two different methods are adopted:the wavelength tracking method and the Fourier-transform white-light interferometry(FTWLI).The sensitivities of sensors with cavity lengths of 288.1 and 358.5 μm are 702.312 nm/RIU and 396.362 μm/RIU,respectively,by the two methods.Our work provides a new kind of RI sensor with the advantages of high sensitivity,mechanical robustness,and low cross sensitivity to temperature.Also,we provide a new method to deal with gold film with a femtosecond laser.