Phase Of Light Wave Research Articles

Complex spatial light modulation capability of a dual layer in-plane switching liquid crystal panel

Complex spatial light modulator (SLM), which can simultaneously control the amplitude and phase of light waves, is a key technology for wide-range of wave-optic technologies including holographic three-dimensional displays. This paper presents a flat panel complex spatial light modulator that consists of dual in-plane switching liquid crystal panels with double-degrees of freedom of voltage inputs. The proposed architecture features single-pixel level complex light modulation enabling complex light modulation in entire free space, which is most contrast to conventional macro-pixel based complex modulation techniques. Its complex light modulation capability is verified with theoretical simulation and experimental characterization, and a three-dimensional holographic image reconstruction without conjugate noise. It is believed that the proposed flat panel complex SLM can be an essential device for a wide range of advanced wave optic technologies.

Secure key distribution based on bidirectional Michelson interferometers.

A scheme based on bidirectional Michelson interferometers to distribute secret keys through the phase of light wave is proposed and demonstrated. The structure uses two optical cable transmission schemes, lasers of short coherent length, random phase drift, polarization random disturbance, and vibration positioning technology to ensure the safe transmission of the secret key. The feasibility of 80 km secret key transmission is verified by experiments. When the secret key is transmitted at the frequency of 200 kHz, the bit error rate is less than 0.3%, and the disturbance positioning accuracy is within $\pm {100}\;{\rm m}$.

Research on the estimation method of the point-of-interest (POI) displacement for ultra-precision flexible motion system based on functional optical fiber sensor

This paper proposes a POI displacement estimation method based on the functional optical fiber sensor and the phase modulation principle to improve the POI displacement estimation accuracy. First, the relation between the object deformation and the optic fiber lightwave phase is explained; the measurement principle of functional optical fiber sensor based on the heterodyne interference principle and its layout optimization method is proposed, and a POI displacement estimation model is presented based on the data approach. Secondly, a beam is taken as the simulation object, the optimal position and length of the optical fiber sensor are determined based on its simulation data. Finally, the experimental device is designed to verify the effectiveness of the POI displacement estimation method based on the optic fiber sensors. The frequency-domain plot of the signals shows that the optical fiber sensors can express the flexible deformation of the analyzed object well. The POI displacement estimation model with the fiber optic sensor signals as one of the inputs is constructed. Through estimating the test data, the error using the optical fiber sensor-based POI displacement estimation method proposed in this paper reduces by more than 61% compared to the rigid body-based assumption estimation method.

Numerical analysis on high resolution optical measurement method with long working distance objective for in-line inspection of micro-structured surface

For in-line surface inspection of microfluidic devices, optical measurement techniques with sub-micrometer resolution and a long working distance (W.D.) objective lens are needed. Structured illumination microscopy (SIM) is a good candidate to achieve high resolution. In micro-structured surface inspection, however, measurement needs to be carried out through coherent imaging, and thus conventional incoherent SIM cannot be applied directly due to interference of light from a sample. In this study, equations are reformulated by considering amplitude and phase of light waves. As a result, we found that higher spatial frequencies of samples can be derived even through coherent imaging by using multiple interference images. Based on this proposed coherent SIM, an optical measurement method with a long W.D. objective lens and sub-micrometer resolution for in-line surface inspection of sub-micro- and micro-structured surfaces is proposed. We analyzed resolution and performance of the proposed method from a theoretical and numerical perspective based on Fourier optics and imaging theory. The results verified that even with a long W.D. objective lens, the concept of the proposed method allows us to achieve sub-micrometer resolution in spite of non-fluorescence observation. This cannot be achieved by standard microscopy and the conventional incoherent SIM. We also conducted numerical analysis considering external disturbance that can occur in practical in-line inspection. The results revealed that the proposed method is capable to resolve two points with a distance less than half a micrometer with the maximum measurement error of no larger than 5%, under the condition where a maximal phase error of reference light is 2π/20 i.e., 20 nm error in length. These values are practical in in-line inspection.

Nonlinear Diatomic Metasurface for Real and Fourier Space Image Encoding.

In linear optics, the metasurface represents an ideal platform for encoding optical information because of its unprecedented abilities of manipulating the intensity, polarization, and phase of light wave with subwavelength meta-atoms. However, controlling various degrees of freedom of light in nonlinear optics remains elusive. Here, we propose a nonlinear plasmonic metasurface working in the near-infrared regime that can simultaneously encode optical images in the real and Fourier spaces. This is achieved by designing a diatomic meta-molecule, which enables the independent control of the nonlinear geometric phase, polarization, and intensity of second harmonic waves. The proposed nonlinear diatomic metasurface provides an ultracompact platform for implementing multidimensional optical information encoding and may hold great potential in optical information security and optical anticounterfeiting.

Optoelectronic THz-Wave Beam Steering by Arrayed Photomixers With Integrated Antennas

We developed a thermo-optic effect based silica optical phased array (OPA) chip and evaluated its tunability of phases of lightwaves. The THz waves, whose phases are controlled by the OPA chip, are generated from four arrayed uni-travelling-carrier photodiodes (UTC-PDs) based on heterodyne photomixng. Meanwhile, the UTC-PDs, which integrated with 4×4 slot antennas, are fabricated on a monolithic InP substrate chip for 300-GHz wave beam combining and steering. Through the optoelectronic THz-wave phase control, the feasibility of 300-GHz beam continuous steering is successfully demonstrated in a range of 50°.

Polarization induced non-reciprocal phase controlled all-fiber loop mirror based inclinometer

An optical fiber inclinometer based on non-reciprocal phase change effect in a single-mode fiber loop mirror (FLM) is proposed. The phase of light waves in FLM is controlled by two-phase shifters (PSs). The relationship between the inclination angles and phase differences of the two-PSs, and transmitted light power was derived by Jones calculus. The signature of the birefringence obtained through simulation on the output light has been confirmed by experimentation. From the results, it was found that when the birefringence of the two-PSs are different, two measurement sensitivities (17.07 × 10−3 deg−1 and 21.37 × 10−3 deg−1) can be realized with one angle measurement system. We also report a method for changing measurable ranges, and measurement sensitivity. Since the angle can be directly measured from the transmitted light power, the results of this work contribute to the realization of simple and low-loss inclinometers using standard single-mode fiber.

Holography microscopy as an artifact-free alternative to phase-contrast.

Artifact-free microscopic images represent a key requirement of multi-parametric image analysis in modern biomedical research. Holography microscopy (HM) is one of the quantitative phase imaging techniques, which has been finding new applications in life science, especially in morphological screening, cell migration, and cancer research. Rather than the classical imaging of absorbing (typically stained) specimens by bright-field microscopy, the information about the light-wave's phase shifts induced by the biological sample is employed for final image reconstruction. In this comparative study, we investigated the usability and the reported advantage of the holography imaging. The claimed halo-free imaging was analyzed compared to the widely used Zernike phase-contrast microscopy. The intensity and phase cross-membrane profiles at the periphery of the cell were quantified. The intensity profile for cells in the phase-contrast images suffers from the significant increase in intensity values around the cell border. On the contrary, no distorted profile is present outside the cell membrane in holography images. The gradual increase in phase shift values is present in the internal part of the cell body projection in holography image. This increase may be related to the increase in the cell internal material according to the dry mass theory. Our experimental data proved the halo-free nature of the holography imaging, which is an important prerequisite of the correct thresholding and cell segmentation, nowadays frequently required in high-content screening and other image-based analysis. Consequently, HM is a method of choice whenever the image analysis relies on the accurate data on cell boundaries.

Compact and stable THz vector spectroscopy using silicon photonics technology

We present a compact and stable terahertz (THz) vector spectroscopy system using silicon photonics technology. A silicon-based integrated phase control circuit greatly reduces the physical size of the continuous-wave THz spectroscopy system and enhances environmental phase stability. Differential lightwave phase control using two carrier-injection electro-optic modulators enables fast and linear phase sweeps of THz-waves. Using the silicon-photonic circuit, we demonstrate a THz vector spectrometer; the dynamic ranges are 65 and 35 dB at 300 GHz and 1 THz with 1-ms integration time and phase variation is less than ± 10° without thermal packaging.

Phase-Adjusting Layers in the Multilayer Reflector of a Jewel Beetle

In this study, we investigated the iridescence of a jewel beetle Chrysochroa fulgidissima , which is one of the most common examples of structural color produced by multilayer optical interference. We performed detailed measurements and analyses of angle- and polarization-dependent reflection spectra and found that a few layers located near the elytron surface play an important role in the coloration mechanism: they adjust the phases of light waves reflected from the lower part of the multilayer structure such that the waves interfere constructively with the reflection at the top surface. This phase adjustment is crucial to the coloration mechanism since the top surface contributes the most to the overall reflection owing to a large refractive-index difference between air and the cuticle. We also found that the jewel beetle exhibits a green-color-dominant iridescence: the blue color observed at oblique angles looks much weaker than the green color at small angles. We elucidated the physical origins of thi...

Reorientation of the liquid crystal director in a Hele-Shaw cell

Reorientation of the liquid crystal (LC) director due to hydrodynamical motions in a Hele-Shaw cell is studied theoretically. These motions arise when LC is pushed by viscous stress of a less viscous fluid or gas (e.g., air). We have obtained the value of 1 rad for the probe light wave phase change at the LC film thickness of 100 μm and pressure gradient of dp/dx = 10−5 Pa/m in the air.

Experimental studies of light-wave phase shift by polymer dispersed liquid crystal films

Experimental studies of light-wave phase shift by polymer dispersed liquid crystal films

Formulation and picture of quantum phase

Based on the concept of classical phase, we formulate a new explanation for the quantum phase from the quantum mechanical point of view. The quantum phase is the canonically conjugate variable of an angular momentum operator, which corresponds to the angular position φ in an actual physical space with a classical reference frame, but it takes a complex exponential form eiφ≡cosφ+i sinφ in the abstract Hilbert space of a quantum reference frame. This formulation is simply the famous Euler formula in a complex number field. In particular, when φ = π/2, the correlative quantum phase is a unitary pure imaginary number eiπ/2≡cos(π/2)+i sin(π/2) ≡ i. By using a photon state-vector function that is the general solution of photon Schrodinger equation and can completely describe a photon’s behavior, we discuss the relationship between the angular momentum of a photon and the phase of the photon; we also analyze the intrinsic relationship between the macroscopic light wave phase and the microscopic photon phase.

Optical processing of holographic lateral shear interferograms recorded by displacing an object

A new approach is considered which is used in holographic lateral shear interferometry and allows the combination of the displacement of a phase object under study during the recording of holographic interferograms with the optical processing of displaced and optically conjugate holographic interferograms. Depending on the method of optical processing of such a pair of holographic interferograms, several aberration-free interference patterns are observed, which reflect with different sensitivities variations in the light wave phase caused by the phase object. Due to the lateral shear, which is equal to or exceeds the linear size of the object, the interference patterns of the object are identical to interference patterns obtained in a two-beam, reference-wave interferometer. The possibility of using this method to control optical inhomogeneities in active crystals in solid-state lasers is studied experimentally.

Synthesis of optical-coherence function and its applications in distributed and multiplexed optical sensing

We have proposed and demonstrated in recent years a unique technique to synthesize the optical-coherence function by manipulating the frequency and the phase of lightwave. Based upon this technique, the synthesis of optical coherence function (SOCF), various distributed photonic sensing and optical-information-processing applications have been developed. In this paper, the principle of SOCF is summarized. A series of functional optical-sensing systems, including fiber-optic reflectometries, distributed stress-location sensors, multiplexed fiber Bragg grating (FBG) sensors, are introduced. Fully distributed fiber-optic strain sensing systems by Brillouin frequency shift are highlighted, and a distributed sensor based on synthesized dynamic grating is also presented. Applications in two- or three-dimensional distributed measurements, such as optical tomography of scattering medium, are also reviewed.

Experimental demonstration of direct-detection quaternary differential polarisation-phase-shift keying with electrical multilevel decision

Direct-detection quaternary differential polarisation-phase-shift keying (DPolPSK) has been experimentally demonstrated for optical communications. DPolPSK encodes information on both the polarisation and phase of lightwave. The polarisation-phase symbols are decoded using optical interferometric demodulation and electrical multilevel decision; no dynamic optical polarisation control is required at the receiver. In the experiment, 20 Gbit/s quaternary DPolPSK was transmitted through 3 x 80 km standard singlemode fibre with a measured BER of less than 10 -11 .

Measurement of wavefront distortions by the method of aperture sounding with spatially separated channels

Features of the formation of signals in wavefront sensors with the single-frequency light wave phase modulation and spatial separation of control channels are considered. Analysis is performed for sensors in which phase modulation is governed by a controlled element located in the pupil of the optical system of a sensor or in the focal plane of the objective of this system. Peculiarities of the signal formation for a tilted wavefront are considered separately for internal points of the exit pupil in the case of light wave phase modulation in the pupil. It is shown that a signal at the modulation frequency in these wavefront sensors for points located far from the pupil boundaries is determined by the wavefront curvature.

Light propagation through a monolayer of discrete scatterers: analysis of coherent transmission and reflection coefficients

An investigation of the coherent transmission and reflection coefficients of a monolayer of spherical scatterers as a function of their size, optical constants, and concentration is carried out. An analysis is performed of the quasi-crystalline approximation of the multiple-wave scattering theory and on the single-scattering approximation (SSA). The results permit determining the limits of applicability of the SSA to the layers with the partial ordering of spherical scatterers in analyzing the phases of the transmitted and the reflected waves. The phase of the transmitted and the reflected waves is investigated in the conditions of the quenching effect. It is shown that in such a case small changes in the refractive index of particles can cause dramatic phase changes. This effect can be used to modulate the light-wave phase, e.g., by electrically controlled composite liquid-crystals films.

Coherent optical associative memory system that processes complex-amplitude information

A novel neural-network system dealing with lightwave phase and amplitude information is constructed as an associative memory. Experiments demonstrate that complex-amplitude vectors embedded in the neural network are recalled successfully. The coherent networks are theoretically expected to realize various attractive neural features in the future, such as carrier-frequency domain parallelism and self-organizing activeness mechanisms. The experimental result leads to such highly functional neural-network architecture and hardware, as well as future quantum neural devices.

Sonic Field Measurement Using Light Computerized Tomography

In this work, we propose a new method of sonic field measurement using light waves. The advantage of using light is to be able to measure sonic fields without contact. The main conventional method involving use of light is sound pressure intensity measurement using optical diffraction of sonic fields. On the other hand, the new method can be used to measure amplitude and phase distributions of sound pressure as a kind of wave field by means of tomography. We perform a simulation assuming a circular ultrasonic transducer. Variations of light wave phase induced by generation of sonic fields are calculated in the simulation. Using the numerical results, we reconstruct the sonic field images. It is confirmed that images of an ultrasonic field can be obtained.