Produce Interference Patterns Research Articles

Isolating the classical and quantum coherence of a multiphoton system

The classical properties of thermal light fields were instrumental in shaping our early understanding of light. Before the invention of the laser, thermal light was used to investigate the wave-particle duality of light. The subsequent formulation of the quantum theory of electromagnetic radiation later confirmed the classical nature of thermal light fields. Here, we fragment a pseudothermal field into its multiparticle constituents to demonstrate that it can host multiphoton dynamics mediated by either classical or quantum properties of coherence. This is shown in a forty-particle system through a process of scattering mediated by twisted paths endowed with orbital angular momentum. This platform enables accurate projections of the scattered pseudothermal system into isolated multiphoton subsystems governed by quantum dynamics. Interestingly, the isolated multiphoton subsystems exhibiting quantum coherence produce interference patterns previously attributed to entangled optical systems. As such, our work unveils novel mechanisms to isolate quantum systems from classical fields. This possibility opens new paradigms in quantum physics with enormous implications for the development of robust quantum technologies.

General Theory of Quantum Holography Based on Two Photon Interference

As a kind of quantum phenomenon, Hong-Ou-Mandel (HOM) interference is more robust against phase noise. Due to this feature, robust quantum holography emerges, through which wave function of interested photon can be retrieved according to HOM interference pattern. For better understanding and developing this method, we derive a theoretical framework of robust HOM holography. In quantum holography scheme, test state and reference state interfere at beam splitter (BS). Then, degree of freedom (DOF) resolved detections (such as spatial resolved detection, temporal resolved detection or spectrum resolved detection) are applied at the BS output ports, respectively. Based on the single photon detection results, the DOF resolved coincidence counts are postselected, producing interference patterns. The information of the test states is retrieved from the patterns. According to different test states and reference states, four combinations are analysed, including measuring the wave function of single photon state using standard single photon state or coherent state and measuring the wave function of coherent state using standard single photon state or coherent state. In all cases, information of the test states is reflected in normalized second-order correlation function or interference patterns in similar forms. Specially, the wave function of test states can be directly retrieved from the interference patterns, with no complex algorithm required. Besides, phase noise from environment has no influence on this kind quantum holography. Comparison between traditional holography and quantum holography is analysed.

General theory of quantum holography based on two-photon Interference

As a kind of quantum phenomenon, Hong-Ou-Mandel (HOM) interference is more robust against phase noise. Because of this feature, robust quantum holography emerges, through which wave function of interested photon can be retrieved according to HOM interference pattern. For better understanding and developing this method, we derive a theoretical framework of robust HOM holography. In the quantum holography scheme, test state and reference state interfere at beam splitter (BS). Then, degree of freedom (DOF) resolved detections (such as spatial resolved detection, temporal resolved detection or spectrum resolved detection) are used at the BS output ports, respectively. Based on the single photon detection results, the DOF resolved coincidence counts are postselected, producing interference patterns. The information of the test states is retrieved from the patterns. According to different test states and reference states, four combinations are analysed, including measuring the wave function of single photon state by using standard single photon state or coherent state and measuring the wave function of coherent state through using standard single photon state or coherent state. In all cases, information of the test states is reflected in normalized second-order correlation function or interference patterns in similar forms. Specially, the wave function of test states can be directly retrieved from the interference patterns, with no complex algorithm required. Besides, phase noise from environment has no influence on this kind quantum holography. Comparison between traditional holography and quantum holography is made and analysed.

An investigation of Aharonov-Bohm effect towards the potential use for the gravitational wave detection

We investigate an alternative way to detect the gravitational wave using the concept of Aharonov-Bohm experiment in curved space-time. Our system consists of an electron beam which is split into two beams passing opposite sides of the solenoid and producing interference patterns. The change in interference patterns can be observed if the system is perturbed by the gravitational wave, and can be used to trace back to the nature of the gravitational wave. This system is described by the cylindrical coordinate in Minkowski space-time where we set the incoming wave propagating in the z-direction, perpendicular to the solenoid’s cross-section. We found that the perturbation on the cross-section area due to gravitational strength is not strong enough to significantly change the phase shift. Contrarily, by changing the magnetic field generated by the current inside the solenoid, the results suggest that the significant phase shift could potentially be detected if the gravitational wave is allowed to propagate in the direction that is perpendicular to z-direction.

Correlating Interference Reflection Microscopy with 3D Superresolution Fluorescence Microscopy

Interference reflection microscopy (IRM) is a widely used technique to study cell adhesion and membrane topography on coverslips due to its easy implementation. It relies on the interference of two reflections, one from the coverslip-buffer interface and the second from the buffer-membrane interface, to produce interference patterns that depend on the distance of the membrane from the coverslip. Additional effects like multiple reflections from more membrane interfaces, tilt of the membrane surface in respect to the coverslip and higher order interference minima and maxima, however, make it hard to correctly interpret the resulting images [1].

Quantum Spin Dynamics in Fock Space Following Quenches: Caustics and Vortices.

Caustics occur widely in dynamics and take on shapes classified by catastrophe theory. At finite wavelengths they produce interference patterns containing networks of vortices (phase singularities). Here we investigate caustics in quantized fields, focusing on the collective dynamics of quantum spins. We show that, following a quench, caustics are generated in the Fock space amplitudes specifying the many-body configuration and which are accessible in experiments with cold atoms, ions, or photons. The granularity of quantum fields removes all singularities, including phase singularities, converting point vortices into nonlocal vortices that annihilate in pairs as the quantization scale is increased. Furthermore, the continuous scaling laws of wave catastrophes are replaced by discrete versions. Such "quantum catastrophes" are expected to be universal dynamical features of quantized fields.

Probing the spatial coherence of wide X-ray beams with Fresnel mirrors at BL25SU of SPring-8.

Probing the spatial coherence of X-rays has become increasingly important when designing advanced optical systems for beamlines at synchrotron radiation sources and free-electron lasers. Double-slit experiments at various slit widths are a typical method of quantitatively measuring the spatial coherence over a wide wavelength range including the X-ray region. However, this method cannot be used for the analysis of spatial coherence when the two evaluation points are separated by a large distance of the order of millimetres owing to the extremely narrow spacing between the interference fringes. A Fresnel-mirror-based optical system can produce interference patterns by crossing two beams from two small mirrors separated in the transverse direction to the X-ray beam. The fringe spacing can be controlled via the incidence angles on the mirrors. In this study, a Fresnel-mirror-based optical system was constructed at the soft X-ray beamline (BL25SU) of SPring-8. The relationship between the coherence and size of the virtual source was quantitatively measured at 300 eV in both the vertical and horizontal directions using the beam. The results obtained indicate that this is a valuable method for the optimization of optical systems along beamlines.

Compact mirror-tunable laser interference system for wafer-scale patterning of grating structures with flexible periodicity

This paper presents a novel mirror-tunable laser interference system for the wafer-scale patterning (>4-in.) of submicron grating structures with a flexible periodicity (200–1000 nm) in a compact and cost-effective manner. The proposed system guides and splits the laser beam into two expanded light beams propagating in a downward direction to be reflected by rotatable ultraviolet mirrors to produce interference patterns. The incident angle of two light beams can be controlled by rotating the mirrors until they match the targeted periodicity of the grating, without the need to reconfigure the optical paths. The fact that light polarization changes with the rotation angle of the mirrors necessitates the use of a half-wave plate along each optical path to adjust the direction of polarization perpendicular to the plane of incident light. The proposed system enables large-area fabrication and wide-range grating tunability, making it highly useful for applications that require wafer-scale patterning of submicron periodic structures, such as flexible wire-grid polarizers for displays, patterned sapphire substrates for light-emitting diodes, and Bragg gratings for distributed feedback lasers.

Near-field observation of surface plasmon polaritons launched by V-shaped nanorods on a gold surface.

By scanning near-field optical microscopy, we study the propagation of surface waves created by V-shaped nanorods deposited on a gold thin film. The nanorods launch surface plasmon polaritons that interfere with the incident light, producing interference patterns. The angle of the V-shaped rods varies from 110° to 180° (straight rod). We observe that the near-field distribution strongly depends on the angle of the V. For angles close to straight rods, a hot spot is visible, whereas for a narrower angle, the surface plasmon waves are launched in specific directions. The experimental results are in good qualitative agreement with numerical simulations performed with a simple analytical model that considers the rods as a sum of isolated surface plasmon sources.

Humidity sensor based on cascaded chirped long-period fiber gratings coated with TiO2/SnO2 composite films

We propose a novel scheme of high-sensitivity relative humidity (RH) sensor based on cascaded chirped long-period fiber gratings (CCLPFG) and sol–gel derived TiO2/SnO2 composite films. Two identical linearly chirped LPFGs without a separation were inscribed into a single-mode fiber core sequentially, which produces interference patterns in the transmission spectrum. The mole ratio of SnO2 is 4% in the sol–gel derived TiO2/SnO2 composite films that were deposited on the cladding surface. The improved adsorption ability of water molecules of the composite films, combined with fine fringe patterns of CCLPFG, enables this sensor to be very sensitive to humidity. In experiment, a wavelength shift of 12.37nm was achieved for RH varying from 40% to 95% at 15°C, which exhibits an approximately linear response. The RH sensitivity of this sensor will slightly decrease for increasing temperature. The sensitivities for 15°C, 20°C, 30°C and 40°C are 0.221nm/%, 0.218nm/%, 0.214nm/% and 0.211nm/%, respectively.

Coherent emitting of multiple sub-beams for small target detection

A method for multiple sub-beams coherently emitting is put forward to improve the ability of laser to detect small targets in a long distance. The laser beam is split into many sub-beams with equal power parallelly emitted to the target in a certain arrangement. The sub-beams produce interference pattern on the target plane due to the fact that they are from the same laser source and have good coherence. Calculated results show that an interference peak is produced. Ideally, the maximum intensity would be N times as large as the intensity of the single beam emitted directly, where N is the number of the sub-beams. The detection is realized by using the interference peaks, and it will benefit especially to the detection of small targets. Beams divergence should be reduced to let a greater power to the target. In order to control the light intensity instability and the spot distortion, the jitters of the emitting mirrors must be controlled as well. Results show that a position accuracy of 0.1λ and an angle accuracy of 0.2θ are needed to have a stable and ideal interference peak, where λ is the wavelength and θ is the divergence angle of the beam.

Bio-Sensing by Mach–Zehnder Interferometer Comprising Doubly-Corrugated Spoofed Surface Plasmon Polariton (DC-SSPP) Waveguide

The paper describes the design and analysis of a Mach-Zehnder interferometer (MZI) structure consisting of doubly-corrugated spoofed surface plasmon polariton (DC-SSPP) waveguide. The dependence of phase change on the dielectric loading of the DC-SSPP structure causes the output from both arms to interfere and enhances features on the transmission spectrum of the MZI. The paper uses a mathematical model to predict the phase accumulation of THz signals travelling through each arm of the MZI with various sample loadings. HFSS simulation has been performed to verify the theoretical modeling and produce more sophisticated results. The paper demonstrates that compared with single-armed SSPP waveguide, the proposed MZI structure shows significant shift of the transmission maxima and minima with high quality factors for the transmission peaks when different materials are loaded. The paper also demonstrates that the proposed DC-SSPP MZI structure can be potentially used in tag-free bio-molecular sensing. The highly localized E-M field at frequencies close to SSPP resonance is shown to reduce the sample amount needed to produce interference patterns without affecting the selectivity of the sensing structure.

Coherent field emission image of graphene predicted with a microscopic theory

Electrons in the mono-layer atomic sheet of graphene have a long coherence length of the order of micrometers. We will show that this coherence is transmitted into the vacuum via electric field assisted electron emission from the graphene edge. The emission current density is given analytically. The parity of the carbon pi-electrons leads to an image whose center is dark as a result of interference. A dragonfly pattern with a dark body perpendicular to the edge is predicted for the armchair edge whose emission current density is vanishing with the mixing angle of the pseudo-spin. The interference pattern may be observed up to temperatures of thousand Kelvin as evidence of coherent field emission. Moreover, this phenomenon leads to a novel coherent electron line source that can produce interference patterns of extended objects with linear sizes comparable to the length of the graphene edge.

Picosecond-Laser 4-Beam-Interference Ablation as a Flexible Tool for Thin Film Microstructuring

Interference of laser beams with the high pulse energy opens an opportunity of direct structuring over large areas. We report results of the laser beam interference ablation of thin metal films on glass using an infrared picosecond laser. The laser beam was split into four beams by a diffractive optical element, and 4F imaging system was used to produce interference pattern on the surface of the metal film. Regular structures with a period of 5μm were produced in thin films of various metals. A variety of periodical patterns can be formed using the method by controlling the process parameters.

Species differences in group size and electrosensory interference in weakly electric fishes: Implications for electrosensory processing

In animals with active sensory systems, group size can have dramatic effects on the sensory information available to individuals. In “wave-type” weakly electric fishes there is a categorical difference in sensory processing between solitary fish and fish in groups: when conspecifics are within about 1 m of each other, the electric fields mix and produce interference patterns that are detected by electroreceptors on each individual. Neural circuits in these animals must therefore process two streams of information—salient signals from prey items and predators and social signals from nearby conspecifics. We investigated the parameters of social signals in two genera of sympatric weakly electric fishes, Apteronotus and Sternopygus, in natural habitats of the Napo River valley in Ecuador and in laboratory settings. Apteronotus were most commonly found in pairs along the Napo River (47% of observations; maximum group size 4) and produced electrosensory interference at rates of 20–300 Hz. In contrast, Sternopygus were alone in 80% of observations (maximum group size 2) in the same region of Ecuador. Similar patterns were observed in laboratory experiments: Apteronotus were in groups and preferentially approached conspecific-like signals in an electrotaxis experiment whereas Sternopygus tended to be solitary and did not approach conspecific-like electrosensory signals. These results demonstrate categorical differences in social electrosensory-related activation of central nervous system circuits that may be related to the evolution of the jamming avoidance response that is used in Apteronotus but not Sternopygus to increase the frequency of electrosensory interference patterns.

Molecular Rotational Excitation by Strong Femtosecond Laser Pulses

We study the rotational wave packet created by nonadiabatic rotational excitation of molecules with strong femtosecond laser pulses. The applicable condition of the Delta-Kick method is obtained by comparing the laser intensity and pulse duration dependences of the wave packet calculated with different methods. The wave packet evolution is traced analytically with the Delta-Kick method. The calculations demonstrate that the rotational populations can be controlled for the rotational wave packet created by two femtosecond laser pulses. The evolution of the rotational wave packet with controlled populations produces interference patterns with exotic spatial symmetries. These calculations are validated by comparing the theoretical calculations with our experimental measurements for the rotational wave packet created by thermal ensemble CO(2) and two strong femtosecond laser pulses. Potential applications in molecular science are also discussed for the rotational wave packet with controlled populations and spatial symmetries.

Controlling molecular rotational population by wave-packet interference

We propose a control scheme for selecting populations of molecular rotational states by wave-packet interference. A series of coherent rotational wave packets is created by nonadiabatic rotational excitation of molecules using two strong femtosecond laser pulses. By adjusting the time delay between the two laser pulses, constructive or destructive interference among these wave packets enables the population to be enhanced or suppressed for a specific rotational state. The evolution of the rotational wave packet with selected populations produces interference patterns with controlled spatial symmetries. This method provides an approach to prepare a molecular ensemble with selected quantum-state distributions and controlled spatial distributions under field-free condition.

Phase-shifting interferometry with four interferograms using linear polarization modulation and a Ronchi grating displaced by only a small unknown amount

A method to reduce the number of captures needed in phase-shifting interferometry is proposed on the basis of grating interferometry and modulation of linear polarization. The case of four interferograms is considered. A common-path interferometer is used with two windows in the object plane and a Ronchi grating as the pupil, thus forming several replicated images of each window over the image plane. The replicated images, under proper matching conditions, superpose in such a way so that they produce interference patterns. Orders 0 and +1 and −1 and 0 form useful patterns to extract the optical phase differences associated to the windows. A phase of π is introduced between these orders using linear polarizing filters placed in the windows and also in the replicated windows, so two π-shifted patterns can be captured in one shot. An unknown translation is then applied to the grating in order to produce another shift in the each pattern. A second and final shot captures these last patterns. The actual grating displacement and the phase shift can be determined according to the method proposed by Kreis before applying proper phase-shifting techniques to finally calculate the phase difference distribution between windows. Related simulations and experimental results are given.

First‐order spatial coherence of indirect excitons in coupled quantum wells

AbstractWe discuss a k∥‐filtering effect for the optical coherence function of indirect excitons in coupled quantum wells. In far‐field optical experiments the light collected from the low‐energy excitons inside the radiative zone produces interference patterns due to the very small difference between their momenta. This small fraction of the exciton distribution is further reduced due to the angular aperture of the experimental apparatus which corresponds to a maximum wavevector and results in a damped oscillatory behavior of the coherence function.Calculation of the optical coherence function above the phase transition temperature yields a coherence length consistent with the experiments, in contrast to the actual coherence length of indirect excitons which is smaller by an order of magnitude. The k∥‐filtering effect can naturally explain the recently observed large coherence lengths without the assumption of a condensed or superfluid phase. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Control on the edge

Surface plasmons can be controlled by designing the edges of metal films to produce interference patterns