Fabry-Perot Interference Effects Research Articles

Fiber-Optic Temperature and Humidity Sensor Based on Fabry-Perot Interference and Anti-Resonance Effect

Fiber-Optic Temperature and Humidity Sensor Based on Fabry-Perot Interference and Anti-Resonance Effect

Simultaneous measurement of salinity and temperature based on Fabry-Perot interference and anti-resonance effect

In this work, we demonstrate a novel cascaded fiber-optic structure depending on Fabry-Perot interference and anti-resonance (AR) effect for seawater salinity and temperature simultaneous measurement. An in-fiber microchannel Fabry-Perot interferometer (FPI) is obtained in a single-mode fiber (SMF) by using femtosecond laser radiation and hydrofluoric acid corrosion, which is filled with thermosensitive polymer and able to measure the temperature. A section of hollow-core fiber (HCF) is fused between the SMFs with the square micro-slots ablated on the ends, and the liquid can easily flow into the HCF. To our knowledge, this is the first time that the capillary-type HCF was used as a microfluidic device to measure seawater salinity. Through model analysis and experimental tests, it is confirmed that the proposed sensor can simultaneously measure the salinity and temperature, the corresponding minimum detectable resolutions reach 0.0008‰ and 0.001 ℃, respectively. The performance tests show that the sensor has accurate measurement results, good stability, and repeatability. Besides, the proposed HCF-based internal liquid analysis structure is a promising approach for highly reliable and ultrasensitive biochemical sensing.

Simultaneous Measurement of Salinity and Temperature Based on Fabry-Perot Interference and Anti-Resonance Effectsimultaneous Measurement of Salinity and Temperature Based on Fabry-Perot Interference and Anti-Resonance Effect

Simultaneous Measurement of Salinity and Temperature Based on Fabry-Perot Interference and Anti-Resonance Effectsimultaneous Measurement of Salinity and Temperature Based on Fabry-Perot Interference and Anti-Resonance Effect

Fabry-Perot interference and piezo-phototronic effect enhanced flexible MoS2 photodetector

Fabry-Perot interference and piezo-phototronic effect enhanced flexible MoS2 photodetector

Third-harmonic generation in multilayer Tin Diselenide under the influence of Fabry-Perot interference effects.

Two-dimensional layered materials are in general known to exhibit strong layer dependent nonlinear optical response owing to the crystal symmetry and associated phase matching considerations. Here we report up-conversion of 1550 nm incident light using third-harmonic generation (THG) in multilayered tin di-selenide (SnSe2) and study its thickness dependence by simultaneously acquiring spatially-resolved images in the forward and backward propagation direction. We find good agreement between the experimental measurements and a coupled-wave equation model we have developed when including the effect of Fabry-Perot interference between the SnSe2 layer and the surrounding medium. We extract the magnitude of the third order electronic nonlinear optical susceptibility of SnSe2, for the first time to our knowledge, by comparing its nonlinear response with a glass substrate and find this to be ∼1500 times higher than that of glass. We also study the polarization dependence and find good agreement with the expected angular dependence of nonlinear polarization considering the crystal symmetry of SnSe2. The large nonlinear optical susceptibility of multi-layer SnSe2 makes it a promising material for studying nonlinear optical effects. This work demonstrates that in addition to the large inherent nonlinear optical susceptibility, the high refractive index of these materials and optical absorption above the bandgap strongly influence the overall nonlinear optical response and its thickness dependence characteristics.

Correction of Fabry-Pérot interference effects in phase and amplitude pulse shapers based on liquid crystal spatial light modulators

Broadband femtosecond laser pulses manipulated by pulse shapers based on a liquid crystal spatial light modulator (LC-SLM) inevitably experience periodic spectral distortions due to Fabry-Perot interference effects within the LC-SLM. We present a method, applicable to phase and amplitude pulse shapers based on dual LC-SLMs, that enables the calibration and suppression of the undesired spectral intensity modulations in a non-iterative fashion. We demonstrate that the method considerably improves the amplitude shaping fidelity of phase and amplitude pulse shapers without compromising the phase shaping properties.

Giant dual-mode graphene-based terahertz modulator enabled by Fabry-Perot assisted multiple reflection.

We report a high-performance terahertz (THz) modulator with dual operation mode. For the pulse operation mode, the proposed THz modulator has the advantage of high modulation depth (MD) and can operate in a broadband frequency range. We have experimentally achieved a MD larger than 90% for the fifth-order pulse THz echo at 0.8THz, and the MD stays larger than 75% in a broadband frequency range larger than 1THz, whereas, for the coherent operation mode, the Fabry-Perot (F-P) interference effect has been taken into consideration and a MD larger than 75% at 0.76THz has also been realized.

Measurement of wavelength-dependent radiation pressure from photon reflection and absorption due to thin film interference

Opto-mechanical forces result from the momentum transfer that occurs during light-matter interactions. One of the most common examples of this phenomenon is the radiation pressure that is exerted on a reflective surface upon photon reflection. For an ideal mirror, the radiation pressure is independent of the wavelength of light and depends only on the incident power. Here we consider a different regime where, for a constant input optical power, wavelength-dependent radiation pressure is observed due to coherent thin film Fabry-Perot interference effects. We perform measurements using a Si microcantilever and utilize an in-situ optical transmission technique to determine the local thickness of the cantilever and the light beam’s angle of incidence. Although Si is absorptive in the visible part of the spectrum, by exploiting the Fabry-Perot modes of the cantilever, we can determine whether momentum is transferred via reflection or absorption by tuning the incident wavelength by only ~20 nm. Finally, we demonstrate that the tunable wavelength excitation measurement can be used to separate photothermal effects and radiation pressure.

Cancellation of Fabry-Perot interference effects in terahertz time-domain spectroscopy of optically thin samples

Cancellation of Fabry-Perot interference effects in terahertz time-domain spectroscopy of optically thin samples

Controllable resonant tunnelling through single-point potentials: A point triode

Abstract A zero-thickness limit of three-layer heterostructures under two bias voltages applied externally, where one of which is supposed to be a gate parameter, is studied. As a result, an effect of controllable resonant tunnelling of electrons through single-point potentials is shown to exist. Therefore the limiting structure may be termed a “point triode” and considered in the theory of point interactions as a new object. The simple limiting analytical expressions adequately describe the resonant behaviour in the transistor with realistic parameter values and thus one can conclude that the zero-range limit of multi-layer structures may be used in fabricating nanodevices. The difference between the resonant tunnelling across single-point potentials and the Fabry–Perot interference effect is also emphasized.

Resonant tunneling and magnetoresistance effect in magnetically modulated graphene

We study resonant tunneling through a magnetic barrier structure in graphene, on the basis of Fabry-Pérot interference effect. For parallel structure, the Fabry-Pérot resonance displays symmetric distribution in (E, ky) space, and the transmission range is shrunk rapidly with the increased magnetic barrier or period number. For antiparallel structure, there exists a complex resonant tunneling caused by the combined effect of Fabry-Pérot resonance and line-type resonance, which are related to resonant states in the vector potential barriers and wells, respectively. Such a transmission difference leads to a giant magnetoresistance ratio which can be effectively controlled by adjusting the magnetic field.

Highly accurate spectral retardance characterization of a liquid crystal retarder including Fabry-Perot interference effects

Multiple-beam Fabry-Perot (FP) interferences occur in liquid crystal retarders (LCR) devoid of an antireflective coating. In this work, a highly accurate method to obtain the spectral retardance of such devices is presented. On the basis of a simple model of the LCR that includes FP effects and by using a voltage transfer function, we show how the FP features in the transmission spectrum can be used to accurately retrieve the ordinary and extraordinary spectral phase delays, and the voltage dependence of the latter. As a consequence, the modulation characteristics of the device are fully determined with high accuracy by means of a few off-state physical parameters which are wavelength-dependent, and a single voltage transfer function that is valid within the spectral range of characterization.

Liquid crystal spatial light modulator with very large phase modulation operating in high harmonic orders

Unusually large phase modulation in a commercial liquid crystal spatial light modulator (LCSLM) is reported. Such a situation is obtained by illuminating with visible light a device designed to operate in the infrared range. The phase modulation range reaches 6π radians in the red region of the visible spectrum and 10π radians in the blue region. Excellent diffraction efficiency in high harmonic orders is demonstrated despite a concomitant and non-negligible Fabry-Perot interference effect. This type of SLM opens the possibility to implement diffractive elements with reduced chromatic dispersion or chromatic control.

Complex Permittivity Determination of Lossy Materials at Millimeter and Terahertz Frequencies Using Free-Space Amplitude Measurements

A free-space measurement method has been proposed for complex permittivity determination of lossy materials at millimeter and terahertz frequencies. The method relies on the Fabry-Perot interference effect between two identical samples separated by a varying air region. We derived a general metric function for fast and accurate complex permittivity determination of lossy materials using intensity data of transmittance power measurements. We have shown that via a graphical method, unique permittivity retrieval is possible using only two measurements of transmittance data corresponding to different distances between identical lossy samples. We have validated the proposed method by performing a numerical analysis.

Using Millimeter and Terahertz Frequencies for Complex Permittivity Retrieval of Low-Loss Materials

A free-space measurement method has been proposed for complex permittivity determination of low-loss materials at millimeter and terahertz frequencies. The method relies on the Fabry-Perot interference effect between two identical samples with different lengths separated by a varying air region. A metric function has been derived for fast and accurate complex permittivity determination of low-loss materials using amplitude-only transmission power data and then we performed its functional analysis to evaluate its dependence on unknown parameters. Next, we employed a graphical method for testing the number of measurements required to extract a unique permittivity. We conclude that 1) at least three independent measurements are required for one permittivity determination and 2) using samples with smaller lengths increases the robustness of the proposed method.

Absorption of resonance radiation and fluorescence of a layer of an atomic gas with thickness of the order of a wavelength

The features of resonance fluorescence and absorption of resonance laser radiation in atomic vapors in a superthin cell with thickness L of the order of a wavelength lambda are investigated theoretically. Taking into account the Fabry-Perot interference effect, it is found that the dependence of the fluorescence and absorption spectra on the ratio L/lambda is substantially different. Coherent spectral narrowing - the Dicke effect - when L=(2n+1)lambda/2 and broadening of the spectral line when L = n lambda (n is a whole number) are observed in the absorption spectra. This effect is absent in the spector of resonance fluorescence in extended media. It is also shown that the processes of saturation and optical pumping significantly alter the spectral line shape as the laser intensity increases; in particular, additional sub-Doppler dips appear at the frequency of the atomic transitions. Calculated curves are given for the D2 lines of ^85Rb atoms. © 2004 Optical Society of America

Finite-difference time-domain analysis of self-focusing in a nonlinear Kerr film

By using a finite-difference time-domain method, we analyze self-focusing effects in a nonlinear Kerr film and demonstrate that the near-field intensity distribution at the film surface can reach a stable state at only a few hundred femtoseconds after the incidence of the beam. Our simulations also show that the formation of multiple filamentations in the near-field is quite sensitive to the thickness of the nonlinear film and the power of the laser beam, strongly indicating the existence of nonlinear Fabry-Perot interference effects of the linearly polarized incident light.

OPTICAL PROPERTIES OF TRIMETHYLBORON AND NITROGEN CODOPED AMORPHOUS CARBON FILMS

We report on the efficient photoluminescence (PL) and optical properties of hydrogenated amorphous carbon thin films codoped with nitrogen and trimethylboron (TMB) grown by rf plasma-enhanced chemical vapor deposition at room temperature. The study clearly shows the observation of discrete PL emission peaks. The PL intensity of the film deposited with 20 sccm TMB is more than 103 times than that of the film deposited without TMB. The change of optical bandgap and PL emission energy with TMB flow rate are discussed based on sp3 and sp2 C networks. Angular dependence of the PL spectra revealed that the origin of multiple sharp peaks is due to Fabry-Perot cavity interference effect.

Ｆｉｂｅｒ Ｂｒａｇｇ Ｇｒａｔｉｎｇを用いた水中音波の検出

A fiber Bragg grating (FBG), which is formed in a fiber core by introducing a periodic variation of the refractive index reflects selectively a particular wavelength of light due to the Bragg reflection. The reflected optical power is modulated if sound pressure is applied to the FBG. Using the FBG which has such a feature we made the fundamental experiments on the detection of underwater sound. Good linearity is obtained under various conditions with the insertion of optical isolators that avoid the fluctuation of detected output due to the Fabry-Perot interference effect between the FBG and the various facets. The sensitivity of detection is maximized if the slope of the curve in the transmittance-wavelength characteristics is steepest at the operating wavelength. Simultaneous multiplex detection is made possible by wavelength division multiplexing with two FBGs in series connection.

Underwater Acoustic Sensor with Fiber Bragg Grating

A new type of underwater acoustic sensor is proposed with an optical fiber Bragg grating (FBG). Because of the photoelasticity with respect to the refractive index and the elasticity of the fiber, the sound pressure in water modulates the Bragg reflection wavelength and, in turn, the intensity of the laser light transmitted through the FBG fiber. Good linearity between the detected signal and the sound pressure is obtained in the range from 81 dB to 140 dB re 1 μPa. Since the upper and lower limits of the acoustic signal level for operation of the sensor are limited by the driving circuit and the transduction of the sound in water, the sensor is expected to operate with much larger dynamic range both at higher and lower pressure levels. Operation of the sensor is very stable with the insertion of optical isolators into the system, although without the isolators the output signal fluctuates at low frequency due to the Fabry-Perot interference effect between the FBG and the various facets.