Digital holographic interferometry applied to the study of tympanic membrane displacements

Quantitative studies of the mechanical properties of tympanic membrane (TM) are needed for better understanding of its role in detailed clinical evaluation, its research being of extreme importance because it is one of the most important structures of the middle ear. By finding the membrane's vibration patterns and quantifying the induced displacement it is possible to characterize and determine its physiological status. Digital holographic interferometry (DHI) has proved to be a reliable optical non-invasive and full-field-of-view technique for the investigation of different mechanical parameters of biological tissues, i.e., DHI has demonstrated an ability to detect displacement changes in quasi-real time and without the need to contact the sample's surface under study providing relevant information, such as clinical and mechanical sample properties. In this research fresh tympanic membrane specimens taken from post-mortem cats are subjected to acoustic stimuli in the audible frequency range producing resonant vibration patterns on the membrane, a feature that results in an ideal application for DHI. An important feature of this approach over other techniques previously used to study the tympanic membrane vibrations is that it only requires two images and less hardware to carry out the measurements, making of DHI a simpler and faster technique as compared to other proposed approaches. The results found show a very good agreement between the present and past measurements from previous research work, showing that DHI is a technique that no doubt will help to improve the understanding of the tympanic membrane's working mechanisms.     

Enhanced phase sensitivity with a nonconventional interferometer and nonlinear phase shifter

We propose a theoretical scheme of an enhanced phase sensitivity by introducing a nonlinear phase shifter to the nonconventional interferometer consisting of a balanced beam splitter (BBS) and an optical parameter amplifier (OPA), a modified nonlinear interferometer (MNI). Then we use coherent state and even coherent state as inputs and homodyne detection at one output port of the MNI for phase sensitivity, both without and with photon losses. We find that the nonlinear phase shifter can not only improve phase sensitivity, but also significantly resist the decoherence from photon losses. In comparison to both the BBS+OPA scheme with linear phase shifter and the traditional Mach–Zehnder interferometer with nonlinear one, the phase sensitivity of the MNI scheme shows the best performance. It is interesting that the nonlinear phase shifter can stimulate potential of the OPA, although there is no improvement in signal-to-noise ratio beyond standard quantum limit for the BBS+OPA scheme with a linear phase shifter.     

Simultaneous manipulation and detection of living cell membrane dynamics

We report a novel optical-tweezers-based method to study the membrane motion at the leading edge of biological cells with nanometer spatial and microsecond temporal resolution. A diffraction-limited laser spot was positioned at the leading edge of a cell, and the forward scattered light was imaged on a quadrant photodiode that served as a position sensitive device. The universality of this technique is demonstrated with different cell types. We investigated the membrane motion at the leading edge of red blood cells in detail and showed that this technique can achieve simultaneous manipulation and detection of cellular edge dynamics with unprecedented precision.     

Ultimate sensitivity of a reflection interferometer with a noninverted instrumental function

Properties of a multiple-beam interferometer with a transmission-like pattern of the fringes in reflected light are considered. A specific feature of this interferometer (a transmission-like reflection interferometer, or TRI) is an asymmetric one-sided mirror with a multilayer dielectric coating and a thin absorbing film. Characteristics of the mirrors and the interferometer as a whole are calculated as functions of the number of dielectric layers. In the calculations, the losses inside the dielectric coating, which are assumed to be concentrated in the vicinity of the layer boundaries, are taken into account. It is shown that a TRI, in terms of its sensitivity, does not differ substantially from conventional multiple-beam interferometers for the same level of technology of the dielectric coatings. The TRI version under consideration demonstrates mode self-filtration, due to which it reflects only the fraction of the incident light corresponding to the resonance of the interferometer. This allows one, in principle, to eliminate special mode cleaners and to significantly simplify the entire optical arrangement.     

一种新型高灵敏度光纤干涉仪

本文提出并分析了一种新型的光纤干涉仪,该仪器对Mach-Zehnder干涉仪作了适当的改进,使灵敏度提高近6倍.通过对干涉仪臂长的适当调节,还可以实现对“共模”噪声的抑制,减小光源波长波动及环境干扰对系统的影响.     

Nonlinear dynamics of the membrane potential of a bursting pacemaker cell

This article presents the results of an exploration of one two-parameter space of the Chay model of a cell excitable membrane. There are two main regions: a peripheral one, where the system dynamics will relax to an equilibrium point, and a central one where the expected dynamics is oscillatory. In the second region, we observe a variety of self-sustained oscillations including periodic oscillation, as well as bursting dynamics of different types. These oscillatory dynamics can be observed as periodic oscillations with different periodicities, and in some cases, as chaotic dynamics. These results, when displayed in bifurcation diagrams, result in complex bifurcation structures, which have been suggested as relevant to understand biological cell signaling.     

Fiber Mach-Zehnder interferometer based on microcavities for high-temperature sensing with high sensitivity

A high-temperature sensor based on a Mach-Zehnder interferometer (MZI) in a conventional single-mode optical fiber is proposed and fabricated by concatenating two microcavities separated by a middle section. A femtosecond laser is used to fabricate a microhole on the center of a fiber end. Then a micro-air-cavity is formed by splicing the microholed fiber end with a normal fiber end. The interferometer is applied for high-temperature sensing, in the range of 500-1200?°C, with a sensitivity of 109 pm/°C that, to the best of our knowledge, is highest in silica fiber temperature sensors. Also, the interferometer is insensitive to external refractive index (RI), which is desirable for temperature sensors.     

Optical methods for the study of dynamics in biological membrane models

Membranes are highly complex and heterogeneous interfaces that are the active partition between living cells and the outside world. Many biologically important processes occur at the membrane surface, such as transmembrane transport and signaling. Many of these processes depend on the subtle interactions between the different membrane constituents: lipids, proteins and water. At present, a large body of knowledge exists on the molecular composition and static structure of membranes. However, our understanding of the dynamics of membrane molecules has not yet reached the same level of sophistication. Information on membrane dynamics, such as conformational fluctuations, conformational changes and dynamical interactions between membrane constituents are essential for a full understanding of membrane action. Here, we review a recently developed approach aimed at obtaining such dynamical information. The approach is based on surface-specific femtosecond laser vibrational spectroscopy, and is illustrated for simple membrane model systems.     

Electronic speckle pattern interferometer design to get maximum sensitivity on the measurement of displacement vector fields

In the present work, different geometries of interferometers with three divergent illumination beams are discussed. It is shown that the sensitivity components for each source can be measured with a maximum weight factor. The three sources were placed respectively, on x, y and near to z axis of a coordinate system. Based on our theoretical calculations it is proposed an interferometer that uses ESPI technique. Experimental results of displacements and strains are presented for one elastic surface when a torsion load is applied near to the target centre.     

Optical characteristics of subwavelength metallic grating coupled porous film surface plasmon resonance sensor with high sensitivity

A high performance sub-wavelength metallic grating coupled surface plasmon resonance (SWMGCSPR) sensor with metal and porous composite layer is proposed. Rigorous coupled-wave analysis (RCWA) is conducted to prove the design feasibility, characterize the sensor's performance and determine geometric parameters of the structure, which is also employed to compute the electromagnetic (EM) field distributions at the resonant wavelengths. Parameters of sensing platform are optimized to achieve the best performance of the SPR sensor. Obtained results reveal that the proposed structure can excite SPR with negative diffraction order of SWMG. Both wavelength and angular sensitivities are greatly enhanced because surface plasmon wave (SPW) exhibits a large penetration depth which will enlarge the distance of interactions between SP and analytes. The detection sensitivities and quality parameters are estimated to be 700 nm/RIU and 509°/RIU with full width at half maximum (FWHM) less than 2.5 nm using the same optimized structure.     

Stable operation of a 300-m laser interferometer with sufficient sensitivity to detect gravitational-wave events within our galaxy

TAMA300, an interferometric gravitational-wave detector with 300-m baseline length, has been developed and operated with sufficient sensitivity to detect gravitational-wave events within our galaxy and sufficient stability for observations; the interferometer was operated for over 10 hours stably and continuously. With a strain-equivalent noise level of h approximately 5x10(-21)/sqrt[Hz], a signal-to-noise ratio of 30 is expected for gravitational waves generated by a coalescence of 1.4M-1.4M binary neutron stars at 10 kpc distance. We evaluated the stability of the detector sensitivity with a 2-week data-taking run, collecting 160 hours of data to be analyzed in the search for gravitational waves.     

Quantum effects of a nonlinear interferometer with a Kerr cell

With the help of the optical Kerr effect we can produce phase fluctuations caused by intensity fluctuations. For this effect we present an exact solution in the Heisenberg picture. Interference of such a light beam with a reference beam produce enhanced bunching as well as antibunching of weak fields.     

Enhancing the sensitivity of an adaptive holographic interferometer using non-Bragg diffraction orders

The signal-to-noise ratio of the output of an adaptive holographic interferometer (AHI) based on a Bi(12)TiO(20) crystal is investigated. We show experimentally that the sensitivity of an AHI using the non-Bragg orders of diffraction in a thin photorefractive material is more than an order of magnitude greater than that of an AHI employing two-wave mixing in photorefractive volume holograms.     

利用共焦球面扫描干涉仪测量压电陶瓷伸长灵敏度

提出了一种测量压电陶瓷伸长灵敏度的新颖方法,此方法利用He-Ne激光器的模式分析实验装置,通过测量相邻两激光干涉序中各对应谱线的电压增量,计算出压电陶瓷的伸长灵敏度.测量过程避免了专用仪器的制造,利用实验室基本设备实现了对压电陶瓷灵敏度的便捷精确测量.     

Experimental intensity patterns obtained from a 2D shearing interferometer with adaptable sensitivity

The interferometric intensity patterns from a 2D shearing interferometer are shown and discussed. The intensity patterns can be obtained in two different approaches incorporating differential and extended wavefront controlled displacements. The reliable directional sensitivity of this interferometer allows the optimization of the measurement parameters to estimate the wavefront of the intensity patterns by regularization techniques.