Common Optical Axis Research Articles

Characterizing quantum gases in time-controlled disorder realizations using cross-correlations of density distributions

The role of disorder on physical systems has been widely studied in the macroscopic and microscopic world. While static disorder is well understood in many cases, the impact of time-dependent disorder on quantum gases is still poorly investigated. In our experimental setup, we introduce and characterize a method capable of producing time-controlled optical-speckle disorder. Experimentally, coherent light illuminates a combination of a static and a rotating diffuser, thereby collecting a spatially varying phase due to the diffusers’ structure and a temporally variable phase due to the relative rotation. Controlling the rotation of the diffuser allows changing the speckle realization or, for future work, the characteristic time scale of the change of the speckle pattern, i.e. the correlation time, matching typical time scales of the quantum gases investigated. We characterize the speckle pattern ex-situ by measuring its intensity distribution cross-correlating different intensity patterns. In-situ, we observe its impact on a molecular Bose–Einstein condensate (BEC) and cross-correlate the density distributions of BECs probed in different speckle realizations. As one diffuser rotates relative to the other around the common optical axis, we trace the optical speckle’s intensity cross-correlations and the quantum gas’ density cross-correlations. Our results show comparable outcomes for both measurement methods. The setup allows us to tune the disorder potential adapted to the characteristics of the quantum gas. These studies pave the way for investigating nonequilibrium physics in interacting quantum gases using controlled dynamical-disorder potentials.

Shape and polarization distribution of non-circular conical diffraction beams from conjugate cascades.

Peculiar non-circularly shaped vector type beams can be obtained naturally by the conical diffraction phenomenon if specific manipulations in wavevector space are performed between optically biaxial crystals arranged in a cascade. We analyze in detail this situation by focusing on the general shapes and the polarization distribution. Both are shown to be correlated to the values of structure parameters introduced in this work. These control parameters depend on the conical diffraction cone aperture angle, on the crystal lengths, and on the magnification values due to x- and y-oriented cylindrical lenses placed between the crystals and coupling common conjugate planes. The local polarization is found to be always linear with the exception of regions where structures composing the pattern intersect or overlap, where elliptical or circular polarization can occur. The way in which the obtained patterns depend on the orientation of individual crystal samples around the common optical axis and on an eventual polarization filtering at various stages of the cascade is discussed as well. Theoretical and experimental findings agree well, as verified for the case of a cascade of two crystals.

Search for sub-eV axion-like particles in a stimulated resonant photon-photon collider with two laser beams based on a novel method to discriminate pressure-independent components

Sub-eV axion-like particles (ALPs) have been searched for by focusing two-color near-infrared pulse lasers into a vacuum along a common optical axis. Within the focused quasi-parallel collision system created by combining a creation field (2.5 mJ/47 fs Ti:Sapphire laser) and a background inducing field (1.5 mJ/9 ns Nd:YAG laser), the detection of signal photons via stimulated resonant photon-photon scattering by exchanging ALPs was attempted in a vacuum chamber. The signal wavelength can be determined via energy-momentum conservation in the vacuum, and it coincides with that determined from the atomic four-wave-mixing (aFWM) process. In this work, the pulse energies were one order of magnitude higher than those in the previous search, allowing aFWM from optical elements to be observed as a pressure-independent background for the first time, in addition to the residual-gas-originating aFWM following a quadratic pressure dependence. In principle the four-wave-mixing process in vacuum via ALP exchanges (vFWM) must also be pressure-independent, so the development of a new method for discriminating the optical-element aFWM is indispensable for increasing the pulse energies to the values needed for future upgraded searches. In this paper, we will present the established method for quantifying the yield from the optical-element aFWM process based on the beam cross- section dependence. With the new method, the number of signal photons was found to be consistent with zero. We then successfully obtained a new exclusion region in the relation between ALP-photon coupling, g/M, and the ALP mass m, reaching the most sensitive point g/M = 1.14 × 10−5 GeV−1 at m = 0.18 eV.

Search for sub-eV axion-like resonance states via stimulated quasi-parallel laser collisions with the parameterization including fully asymmetric collisional geometry

We have searched for axion-like resonance states by colliding optical photons in a focused laser field (creation beam) by adding another laser field (inducing beam) for stimulation of the resonance decays, where frequency-converted signal photons can be created as a result of stimulated photon-photon scattering via exchanges of axion-like resonances. A quasi-parallel collision system (QPS) in such a focused field allows access to the sub-eV mass range of resonance particles. In past searches in QPS, for simplicity, we interpreted the scattering rate based on an analytically calculable symmetric collision geometry in both incident angles and incident energies by partially implementing the asymmetric nature to meet the actual experimental conditions. In this paper, we present new search results based on a complete parameterization including fully asymmetric collisional geometries. In particular, we combined a linearly polarized creation laser and a circularly polarized inducing laser to match the new parameterization. A 0.10 mJ/31 fs Ti:sapphire laser pulse and a 0.20 mJ/9 ns Nd:YAG laser pulse were spatiotemporally synchronized by sharing a common optical axis and focused into the vacuum system. Under a condition in which atomic background processes were completely negligible, no significant scattering signal was observed at the vacuum pressure of 2.6 × 10−5 Pa, thereby providing upper bounds on the coupling-mass relation by assuming exchanges of scalar and pseudoscalar fields at a 95% confidence level in the sub-eV mass range.

Gradient pretilt angle alignment materials with different photosensitivity for tunable polarization‐independent self‐aligned liquid crystal lens

AbstractAlignment of benzaldehyde materials with different photosensitivity thresholds, capable of changing the pretilt angles of nematic liquid crystal (LC) from 90° to 0° in a controlled manner under UV‐B exposure, has been developed. Inhomogeneous exposure of uniform rubbed alignment layers allows the formation of a refractive index gradient inside the LC cell. The concept of tunable polarization‐independent self‐aligned LC lens based on gradient pretilt angle alignment materials with different photosensitivity is demonstrated. Self‐alignment of two polarization‐dependent sub‐lens is achieved due to a single exposure act of two alignment layers, which are located on the same piece of glass on both sides, forming one common optical axis for a polarization‐independent LC lens. The sub‐lens cells have uniform cell gap and are independently controlled using low‐voltage driving. Devices based on gradient benzaldehyde alignment materials can be used in many modern optical and photonic devices.

Extended search for sub-eV axion-like resonances via four-wave mixing with a quasi-parallel laser collider in a high-quality vacuum system

Abstract Resonance states of axion-like particles were searched for via four-wave mixing by focusing two-color pulsed lasers into a quasi-vacuum. A quasi-parallel collision system that allows probing of the sub-eV mass range was realized by focusing the combined laser fields with an off-axis parabolic mirror. A 0.10 mJ/34 fs Ti:sapphire laser pulse and a 0.14 mJ/9 ns Nd:YAG laser pulse were spatiotemporally synchronized by sharing a common optical axis and focused into the vacuum system. No significant four-wave mixing signal was observed at the vacuum pressure of $3.7 \times 10^{-5}$ Pa, thereby providing upper bounds on the coupling-mass relation by assuming exchanges of scalar and pseudoscalar fields at a 95% confidence level in the mass range below 0.21 eV. For this search, the experimental setup was substantially upgraded so that the optical components were compatible with the requirements of the high-quality vacuum system, hence enabling the pulse power to be increased. With the increased pulse power, a new kind of pressure-dependent background photon emerged in addition to the known atomic four-wave mixing process. This paper shows the pressure dependence of these background photons and how to handle them in the search.

GRADIENT ALIGNMENT MATERIALS WITH DIFFERENT PHOTOSENSITIVITY FOR TUNABLE POLARIZATION-INDEPENDENT LIQUID CRYSTAL LENS

The development of electrically tunable liquid crystal (LC) lenses is perspective and promising for a wide range of applications, for example, for imaging system, pico projectors, optical zoom systems, ophthalmology applications and other. Of particular note is the development of polarization-independent LC lenses, as eliminates polarizers from application devices that reduce the efficiency of light transmission through optical systems. Alignment benzaldehyde photosensitive materials, capable of changing the pretilt angles of nematic LC from 90 to 0 ºС in a controlled manner under UV exposure are developed. The anisotropy of the benzaldehyde alignment layers is generated by a two-stage treatment consisting of uniform rubbing with a cloth and subsequent non-polarized UV exposure. Inhomogeneous UV exposure of uniformly rubbed alignment layers allows formation of refractive index gradient inside the LC cell. The concept of tunable polarization-independent self-aligned LC lens based on gradient pretilt angle alignment materials with different photosensitivity is demonstrated. Self-alignment of two polarization-dependent sub-lens is achieved due to a single UV exposure act of two alignment layers, which are located on the same piece of glass on both sides, forming one common optical axis for a polarization-independent LC lens. The independence of the polarization of LC lenses is achieved by setting the azimuthal rubbing direction of the alignment layers of two polarizationdependent LC lenses perpendicular to each other. The sub-lens cells have uniform cell gap and are independently controlled using low-voltage driving. Devices based on gradient benzaldehyde alignment materials can be used in many modern optical and photonic devices.

A JOINT CALIBRATION METHOD OF 3D IMAGES ACQUIRED BY COMMON OPTICAL PATH PAYLOAD

Abstract. The common optical path payload is a new type of imaging payload that can acquire LiDAR data and CCD images simultaneously. This new payload integrates the linear LiDAR and linear CCD images according to the common optical system, and achieves the registration of LiDAR point cloud and CCD images by the alignment of common aperture optical axis and time synchronization control in the front of hardware. Based on the fixed matching relationship between CCD probes and LiDAR probes offered by optical path of common, this paper proposes a joint calibration method, which reduces the ranging error and misalignment error. And the results verify that this method can effectively improve the quality of the three-dimensional images. The standard deviations of validation area and roof are improved from 0.54 m to 0.14 m and 1.83 m to 0.26 m respectively.

Ray tracing in monocentric and ball lenses by a general exact formula.

In this work, we derive a general ray-tracing formula for monocentric lenses based on a linear form of Snell's law. From this formula, we can directly get the meridional formula for a single symmetric (or asymmetric) monocentric lens. All of these formulas can be reduced to their corresponding paraxial forms, and their spherical aberration exact formulas can be easily derived. Also, we easily apply this general formula to get the position of the final image formed by a system of monocentric lenses having a common optical axis. The successive lenses of this system can be a mixture of different monocentric lenses of any kind having known separation distances between their centers. We have no need to apply Snell's law in its trigonometric form, no need to determine the angles of incidence or refraction, and no need to know the height of the ray at any point along its path. If the ray between any two lenses crosses the optical axis, the procedure will continue without any change and without adding any special equations. We also provide an exact procedure to trace a skew ray through a system of monocentric lenses that can be centered or decentered. In this procedure, we have no need to determine the points of incidence or the normal to the surface. The contribution of the procedure in this work is that we can apply our equations lens by lens, and not surface by surface, as in classical ray-tracing methods. This greatly reduces effort and mathematical complexity.

Imaging with two skew ideal lenses.

In lens systems, the constituent lenses usually share a common optical axis, or at least a common optical-axis direction, and such combinations of lenses are well understood. However, in recent proposals for lens-based transformation-optics devices [Opt. Express26, 17872 (2018)OPEXFF1094-408710.1364/OE.26.017872], the lenses do not share an optical-axis direction. To facilitate the understanding of such lens systems, we describe here combinations of two ideal lenses in any arbitrary arrangement as a single ideal lens. This description has the potential to become an important tool in understanding novel optical instruments enabled by skew-lens combinations.

Suppression of Distortions in the X-Ray Fourier-Transform Holography Scheme Based on the Two-Block Fresnel Zone Plate Interferometer with Common Optical Axis

Strict requirements were imposed on the sizes of testing sample in the previously suggested scheme of hard X-ray Fourier-transform holography based on a two-block Fresnel zone plate interferometer with common optical axis. The failure of these requirements leads to appearance of noise in the reconstructed image. In this work, the mechanism of noise formation, as well as possibility of its suppression are considered.

Axially distributed sensing with a monoscopic imaging lens for single-shot distance measurements.

Using the image-based optical measurement method known as axially distributed sensing (ADS), the depth information of a scene is retrieved by evaluating images recorded with a camera positioned on multiple points along a common optical axis. We describe the design of a monoscopic lens that images the scene from two different on-axis points of perspective simultaneously onto a single camera. Designed for use in a territorial surveillance video system, this lens allows for capturing 3D scene information based on ADS with a single shot. We present the physical foundations of this approach and its implementation as a compact lens system and show the usability of the system prototype, supported by performance tests.

Development of Scanning-Imaging X-Ray Microscope for Quantitative Three-Dimensional Phase Contrast Microimaging

A novel x-ray microscope system has been developed for the purpose of quantitative and sensitive three-dimensional (3D) phase-contrast x-ray microimaging. The optical system is a hybrid that consists of a scanning microscope optics with a one-dimensional (1D) focusing (line-focusing) device and an imaging microscope optics with a 1D objective. These two optics are orthogonally arranged regarding their common optical axis. Each is used for forming each dimension of two-dimensional (2D) image. The same data acquisition process as that of the scanning microscope system enables quantitative and sensitive x-ray imaging such as phase contrast and absorption contrast. Because a 2D image is measured with only 1D translation scan, much shorter measurement time than that of conventional scanning optics has been realized. By combining a computed tomography (CT) technique, some 3D CT application examples are demonstrated

Synchrotron infrared confocal microscope: Application to infrared 3D spectral imaging

The brightness of a synchrotron source coupled to an infrared microscope allows imaging at the so-called diffraction limit. Thus, numerous infrared beamlines around the world have been developed for infrared chemical imaging. Infrared microscopes employ Schwarzschild objectives, which are based on two spherical mirrors centered on a common optical axis. A common drawback of the latter design comes with the central obscuring of the incident beam and the corresponding diffraction effects. However, in this work we are taking advantage of the "shadow" below the primary mirror in order to "vertically" probe our sample and record depth profiling images. We recorded infrared confocal images of liquid water occluded inside a quartz micro-cavity and reconstructed a 3D infrared image based on the OH stretching vibrational bands. Although only a restricted sample size can be analyzed, we demonstrate here the feasibility of a 3D confocal infrared measurement. The chemical profiles have been calculated along the Z-axis of the water inclusion to study its heterogeneity and water-solid interfaces.

Visualization of 3D Objects in Scattering Medium Using Axially Distributed Sensing

We present a method to visualize 3D objects in scattering media using the axially distributed sensing method. The scattered elemental images of the 3D objects in scattering media are obtained by moving the camera along the common optical axis. To reduce the scattering effect of the recorded elemental images, a statistical image processing algorithm is applied to the scattering elemental images and the estimated elemental images with the reduced scattering effects are obtained. The estimated elemental images of the objects are used to visualize the 3D scene using the computational reconstruction algorithm based on ray back-projection. We present preliminary experimental results to illustrate how the scattering effects may be reduced by the proposed method.

Optical implementation of multifocal programmable lens with single and multiple axes

In this work we analyse the generation of a diffractive optical element (DOE) consisting of a multifocal Fresnel lens by means of an LCoS (liquid cristal on silicon) spatial light modulator (SLM). The multifocal lens is composed of a set of lenses of different focal length that share a common optical axis (coaxial combination) or have different axes in parallel (multi-axis combination). For both configurations, we present several ways to combine the phase distributions for three lenses with different focal lengths (f1, f2, f3), into a single-phase distribution addressed to the SLM. Numerical simulations were carried out along with the experimental analysis to corroborate the results.

Three-dimensional optical microscopy using axially distributed image sensing

We propose three-dimensional (3D) optical microscopy using axially distributed image sensing. In the proposed method, the micro-objects are optically magnified and their axially distributed images are recorded by moving the image sensor along a common optical axis. The 3D volumetric images are generated from the recorded axial image set using a computational reconstruction algorithm based on ray backprojection. Preliminary experimental results are presented. To the best of our knowledge, this is the first report on 3D optical microscopy using axially distributed sensing.

A coaxial optical scanner for synchronous acquisition of 3D geometry and surface reflectance

We present a novel optical setup and processing pipeline for measuring the 3D geometry and spatially-varying surface reflectance of physical objects. Central to our design is a digital camera and a high frequency spatially-modulated light source aligned to share a common focal point and optical axis. Pairs of such devices allow capturing a sequence of images from which precise measurements of geometry and reflectance can be recovered. Our approach is enabled by two technical contributions: a new active multiview stereo algorithm and an analysis of light descattering that has important implications for image-based reflectometry. We show that the geometry measured by our scanner is accurate to within 50 microns at a resolution of roughly 200 microns and that the reflectance agrees with reference data to within 5.5%. Additionally, we present an image relighting application and show renderings that agree very well with reference images at light and view positions far from those that were initially measured.

A coaxial optical scanner for synchronous acquisition of 3D geometry and surface reflectance

We present a novel optical setup and processing pipeline for measuring the 3D geometry and spatially-varying surface reflectance of physical objects. Central to our design is a digital camera and a high frequency spatially-modulated light source aligned to share a common focal point and optical axis. Pairs of such devices allow capturing a sequence of images from which precise measurements of geometry and reflectance can be recovered. Our approach is enabled by two technical contributions: a new active multiview stereo algorithm and an analysis of light descattering that has important implications for image-based reflectometry. We show that the geometry measured by our scanner is accurate to within 50 microns at a resolution of roughly 200 microns and that the reflectance agrees with reference data to within 5.5%. Additionally, we present an image relighting application and show renderings that agree very well with reference images at light and view positions far from those that were initially measured.

3D imaging with axially distributed sensing

A new (to our knowledge) multiperspective 3D imaging architecture is proposed that uses imagers distributed along a common optical axis. In this axially distributed sensing method, either a single imager is translated along its optical axis or objects are moved parallel to the optical axis of a single imager. The 3D information collection capability of the proposed architecture is analyzed and a computational 3D reconstruction algorithm based on ray back-projection is proposed. It is shown analytically and experimentally that the collection capacity of this architecture is not uniform over the field of view. Experimental results are presented to verify the proposed approach. We believe this is the first report on 3D sensing and imaging with axially distributed sensing.