Design of three-primary-color filter based on structure of three-cavity Fabry–Perot color filter

Optical and Quantum Electronics - Elastic optical network (EON) is considered as the platform for future optical transport networks. Routing and spectrum allocation (RSA) has a significant bearing...     

Temperature-independent refractometer based on fiber-optic Fabry–Perot interferometer

A miniature fiber-optic refractometer based on Fabry–Perot interferometer (FPI) has been proposed and experimentally demonstrated. The sensing head consists of a short section of photonics crystal fiber (PCF) spliced to a single mode fiber (SMF), in which the end-face of the PCF is etched to remove holey structure with hydrofluoric (HF) acid. A Fabry–Perot interference spectrum is achieved based on the reflections from the fusion splicing interface and the end-face of the core of PCF. The interference fringe is sensitive to the external refractive index (RI) with an intensity-referenced sensitivity of 358.27 dB/RIU ranging from 1.33 to 1.38. The sensor has also been implemented for the concentration measurement of λ-phage DNA solution. In addition, the dip intensity is insensitive to the ambient temperature variation, making it a good candidate for temperature-independent bio-sensing area.     

Thermal characteristics of Fabry–Perot cavity based on regenerated fiber Bragg gratings

The Letter reports the thermal stability and strain response of Fabry–Perot(FP) cavity under different high temperatures. The FP cavity was made by thermal regeneration of two identical cascaded fiber Bragg gratings(FBGs). It is demonstrated that the FP cavity is capable of measuring temperatures from 300℃ to 900℃ with a temperature sensitivity of 15.97 pm/℃. The elongation of the fiber was observed through the drifted Bragg wavelength at 700℃ or above when weight was loaded. The elongation was further inferred by the slight change in the interference spectra of the FP cavity at 900℃.     

Reconstruction of Fabry–Perot cavity interferometer nanometer micro-displacement based on Hilbert transform

A novel reconstruction method of nanometer micro-displacement of Fabry–Perot(F-P) interference is proposed in this study. Hilbert transforms are performed for F-P interference fringes, and the obtained signal performs tangent operation with the original signal. Finally, the validity of the proposed algorithm and the structure are verified by simulation and several experimental measurements for vibration. Results from the experiments show that the maximum relative error is 4.9%.     

Fabry–Perot effect on dimer nanoantennas

In this work, we investigate the interaction between a single quantum emitter and dimer nanoantennas through a Fabry–Perot structure composed of an appropriate combination of two dielectric layers. This type of dielectric configuration is well known in the microwave region to increase the antenna performance, such as directivity, radiation efficiency, and radiation resistance. Here, the Fabry–Perot concept is transposed to the optical domain. The single emitter couples to the antenna through the dielectric structure, giving rise to a wide aperture field on top of the dielectrics with the same polarization of the emitter. This purely polarized aperture field can be used to excite one or more conveniently spaced nanoantennas. We demonstrate by 3D numerical calculations that the directivity and excitation rate of a single dimer is highly increased. Also, we show that multiple dimers arranged in an array configuration can be enhanced due to the wide aperture field generated by a single emitter.     

Optical properties of Fabry–Perot microcavity with organic light emitting materials

We investigated the optical properties of the tris(8-hydroxyquinoline)aluminum (Alq₃) organic film with Fabry–Perot microcavity by measuring photoluminescence (PL) and transmittance. We have simulated the phase change on reflection as a function of wavelength. The Fabry–Perot microcavity structures were designed according to the simulation results and the resonant wavelength corresponding to the maximum of PL spectrum of a bare Alq₃ film. These structures were fabricated in three types of microcavities, such as type A [air|metal|Alq₃|metal|glass], type B [air|dielectric|Alq₃|dielectric|glass], and type C [air|metal|Alq₃|dielectric|glass]. A bare Alq₃ layer on glass, [air|Alq₃|glass], showed a PL peak around 514 nm and its full width at half maximum (FWHM) was about 80 nm. The broad FWHM of the bare Alq₃ film was reduced to 15–27.5, 7–10.5 and 16–16.6 nm for three types by cavity effects. Also, the control of the resonant wavelength can be achieved by the spacer length as well as the phase change on reflection on mirror.     

Performance comparison of Fabry–Perot and Mach–Zehnder interferometers for molecular Doppler lidar based on fringe-imaging technique

Fringe-imaging Fabry–Perot interferometer (FIFPI) and fringe-imaging Mach–Zehnder interferometer (FIMZI) used as frequency discriminator for incoherent molecular Doppler lidar were analyzed, respectively. For a pure molecular backscattered signal, performances (wind measurement sensitivity and signal-to-noise ratio) of both FIFPI and FIMZI systems were simulated based on the U.S. standard atmospheric model. Comparisons of two systems were made under the same emitting and receiving parameters with certain wind speed dynamic range. Simulated results show that, though relatively lower sensitivity to Doppler shift, the single-channel FIMZI system provides a factor of 1.3 times smaller error in the horizontal wind velocity than that of FIFPI at a range of 20 km. We expect that the FIMZI frequency discriminator would provide an effective technique to improve the measurement accuracy for incoherent molecular Doppler lidar.     

Design of low frequency fiber optic Fabry–Perot seismometer based on transfer function analysis

We develop a low frequency fiber Fabry–Perot(F-P) seismometer based on transfer function analysis. The seismometer structure and demodulation system accuracy are limitations of low frequency seismic monitoring. The transfer function of the F-P seismometer is analyzed, and the mass displacement spectrum(MDS) is introduced. MDS provides guidance for mechanical structure design and optical interferometer analysis to achieve low noise. The F-P seismometer prototype is built. The experiment shows that the prototype has an average noise of 6.74 ng=p Hz below 50 Hz, and its noise is less than that of the global new high noise model within 0.16–50 Hz, whose potential is considerable.     

High resolution inclinometer based on vertical pendulum and fiber Bragg grating Fabry–Perot cavity

In this paper, an inclinometer based on a vertical pendulum and a fiber Bragg grating Fabry–Perot cavity(FBG-FP) is proposed. A low-damping rotation structure is used to reduce the mechanical frictions of the pendulum system and induce a wavelength shift of FBG-FPs. We find that the sensitivity can be maximized by optimizing the parameters of the inclinometer. Using a high-resolution demodulation system, a sensitivity of179.9 pm/(°), and a resolution better than 0.0200 can be achieved. Experiments also show that the proposed inclinometer has good linearity and repeatability.     

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.     

Temperature self-compensation fiber-optic pressure sensor based on fiber Bragg grating and Fabry–Perot interference multiplexing

A high performance multiplexed fiber-optic sensor consisted of diaphragm-based extrinsic Fabry–Perot interferometer (DEFPI) and fiber Bragg grating (FBG) is proposed. The novel structure DEFPI fabricated with laser heating fusion technique possesses high sensitivity with 5.35 nm/kPa (36.89 nm/psi) and exhibits ultra-low temperature dependence with 0.015 nm/°C. But the ultra-low temperature dependence still results in small pressure measurement error of the DEFPI (0.0028 kPa/°C). The designed stainless epoxy-free packaging structure guarantees the FBG to be only sensitive to temperature. The temperature information is created to calibrate the DEFPI's pressure measurement error induced by the temperature dependence, realizing effectively temperature self-compensation of the multiplexed sensor. The sensitivity of the FBG is 10.5 pm/°C. In addition, the multiplexed sensor is also very easy to realize the pressure and the temperature high-precise high-sensitive simultaneous measurement at single point in many harsh environmental areas.     

Optical Fabry–Perot filter based on photonic band gap quasi-periodic one-dimensional multilayer according to the definite Rudin–Shapiro distribution

In this work, a new type of optical filter using photonic band gap materials has been suggested. Indeed, a combination of periodic H(LH)^J and Rudin–Shapiro quasi-periodic one-dimensional photonic multilayer systems (RSM) were used. SiO₂ (L) and TiO₂ (H) were chosen as two elementary layers with refractive indexes n_L = 1.45 and n_H = 2.30 respectively. The study configuration is H(LH)^J[RSM]^PH(LH)^J, which forms an effective Fabry–Perot filter (FPF), where J and P are respectively the repetition number of periodic and (RSM) stacks. We have numerically investigated by means of transfer-matrix approach the transmission properties in the visible spectral range of FPF system. We show that the number and position of resonator peaks are dependent on the (RSM) repetition number P and incidence angle of exciting light. The effect of these two parameters for producing an improved polychromatic filter with high finesse coefficient (F) and quality factor (Q) is studied in details.     

Temperature-independent optical fiber Fabry–Perot refractive-index sensor based on hollow-core photonic crystal fiber

A novel optical fiber refractive index (RI) sensor, which is based on an intrinsic Fabry–Perot interferometer (IFPI) formed by a section of hollow-core photonic crystal fiber (HCPCF) and standard single mode fibers (SMF), is proposed. The external refractive index is determined according to the maximum fringe contrast of the interference fringes in the reflective spectrum of the sensor. The RI response performance is demonstrated for the measurement of the different RI solutions. The experimental data agree well with the theoretical results. Also the RI resolution and repeatability of ∼1.5 × 10⁻⁵ and ±0.5% in the linear measurement region, are achieved. In addition, the temperature response is tested from 20 °C to 120 °C, which exhibits excellent thermal stability. Therefore, such an HCPCF-based F–P sensor provides a practical way to measure RI with non-temperature compensation.     

Dynamical behaviour of birefringent Fabry–Perot cavities

In this paper we present a theoretical and experimental study of the dynamical behaviour of birefringent cavities. Our experimental data show that usual hypothesis which provides that a Fabry–Perot cavity is a first-order low-pass filter cannot explain the behaviour of a birefringent cavity. We explain this phenomenon and give the theoretical expression of the equivalent cavity filter which corresponds to a second-order low-pass filter.     

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.     

Considerations on parametric instability in Fabry–Perot interferometer

We evaluate the parametric phenomenon for the main optical mode coupled to other resonant waves excited by acoustic interaction with the mirrors of a Fabry–Perot. We apply this to the arm cavity of a gravitational wave antenna. Under certain assumptions we find that the amplitude of these parasitic modes is expressed by analytic solutions that are always damped. We analyze both the zero detuning and the detuned case and solve the equations. The form of the solution shows that for equally spaced and excited cavity modes the instability is expressed by a threshold condition, which is well approximated for LIGO arm resonator parameters.     

Design of thermo-optic tunable optical filter based on Si/Air DBR and polymer Fabry–Perot microcavity in SOI

An integrated tunable optical filter (TOF) based on thermo-optic effect in silicon on insulator (SOI) rib waveguide is designed and simulated. The device is comprised of two high refractivity contrast Si/Air stacks, functioning as high reflectivity of DBRs (distributed Bragg reflectors) and separating by a variable refractive index polymer Fabry–Perot (F–P) cavity. The designed device exhibits Q = 24077, FWHM = 0.065 nm and finesse = 566. Wavelength tuning is achieved through thermal modulation of refractive variation of the cavity. As the cavity polymer is heated, the refractive index of the cavity decreases. When the temperature of cavity polymer changes within 105, the central wavelength gets a continuous 35 nm shift from 1530 nm to 1565 nm, which can operate the whole C-band in the WDM (wavelength division multiplexing) networks. Moreover, by calculating, the tuning sensitivity is about 0.33 nm/°C. Owing to the compact size and excellent characteristics of integration, the proposed component has a promising utilization in spectroscopy and optical communication.     

Wavelength modulation spectroscopy at 1530.32 nm for measurements of acetylene based on Fabry–Perot tunable filter

Sensitive detection of acetylene(C_2H_2) is performed by absorption spectroscopy and wavelength modulation spectroscopy(WMS) based on Fiber Fabry–Perot tunable filter(FFP-TF) at 1530.32 nm. After being calibrated by Fiber Bragg Grating(FBG), FFP-TF is frequency-multiplexed and modulated at 20 Hz and 2.5 kHz respectively to achieve wavelength modulation. The linearity with 0.9907 fitting coefficient is obtained by measuring different concentrations in a 100 ppmv–400 ppmv range. Furthermore, the stability of the system is analyzed by detecting 50 ppmv and 100 ppmv standard gases for 2 h under room temperature and ambient pressure conditions respectively. The precision of 11 ppmv is achieved by calculating the standard deviation. Therefore, the measuring system of C_2H_2 detection can be applied in practical applications.