Design Of Interferometer Research Articles

Design and simulation of interferometer for synchrotron radiation beam size measurement

The interferometric measurement of the transverse beam size based on synchrotron radiation is a non-intercepting high precision measurement method. Compared with the imaging method, the interferometric method can measure smaller beam size and get better resolution. It is expected to obtain submicron resolution at shorter measurement wavelength, so it is widely used in synchrotron radiation sources. The upgraded scheme of current interference device in Hefei Light Source HLS-II is presented in this paper. It is proposed to replace the first focusing lens in the original interference light path with an RC structure focusing mirror, and the second single lens with a doublet lens. The design goal of this paper is to reduce dispersion and geometric aberration without changing the optical axis of the optical path, so as to improve the imaging quality of the optical path. The geometrical optical path design is used to evaluate the imaging quality of the optical path, and physical optical simulation is performed to obtain the interference fringes of the measurement system. The simulation results show that the radius of Airy spot is reduced by about 35%, the root mean square radius of dot array is reduced by about 99%, the wavefront difference is reduced by about 75%, and the cutoff frequency of MTF function is increased by about 65%, using a focusing mirror to replace the original focusing lens can greatly improve the image quality of the optical path.

A compact 100 GHz femtojoule silicon-organic hybrid modulator based on a novel Mach–Zehnder interferometer design

In this paper, a high-speed, low-power and compact silicon-organic hybrid (SOH) modulator operating at the telecom wavelength is presented. The modulator is based on the mature and widespread silicon-on-insulator technology with a device layer of 220 nm. The proposed design utilizes a slot waveguide in a loop-terminated Mach–Zehnder interferometer (LT-MZI) configuration. The LT-MZI is twice as compact as the conventional MZI. Accordingly, the LT-MZI modulator exhibits a reduction in capacitance by a factor of two, which subsequently enhances the modulator speed and power consumption by a factor of two. An electro-optic polymer is used as it exhibits fast and strong electro-optic effects. Finite element and finite difference simulations show that for a driving voltage of only 0.5 V our modulator arms’ length is as low as 167 µm resulting in a Vπ × L product of only 0.084 V mm, 10.41 fF capacitance and up to 100 GHz speed with corresponding energy consumption of only 6.755 fJ bit−1. Results based on 3D finite difference time domain simulation show that our modulator can work over a large optical bandwidth of 60 nm with an extinction ratio (ER) greater than 23 dB and insertion loss (IL) less than 1.7 dB, reaching ER = 40 dB and IL = 1.15 dB at λ = 1.55 µm.

The Tianlai dish pathfinder array: design, operation, and performance of a prototype transit radio interferometer

ABSTRACT The Tianlai Dish Pathfinder Array is a radio interferometer designed to test techniques for 21 cm intensity mapping in the post-reionization universe as a means for measuring large-scale cosmic structure. It performs drift scans of the sky at constant declination. We describe the design, calibration, noise level, and stability of this instrument based on the analysis of about 5% of 6200 h of on-sky observations through 2019 October. Beam pattern determinations using drones and the transit of bright sources are in good agreement, and compatible with electromagnetic simulations. Combining all the baselines, we make maps around bright sources and show that the array behaves as expected. A few hundred hours of observations at different declinations have been used to study the array geometry and pointing imperfections, as well as the instrument noise behaviour. We show that the system temperature is below 80 K for most feed antennas and that noise fluctuations decrease as expected with integration time, at least up to a few hundred seconds. Analysis of long integrations, from 10 nights of observations of the North Celestial Pole (NCP), yielded visibilities with amplitudes of 20–30 mK, consistent with the expected signal from the NCP radio sky with ${\lt}10\,$ mK precision for 1 MHz × 1 min binning. Hi-pass filtering the spectra to remove smooth spectrum signal yields a residual consistent with zero signal at the $0.5\,$ mK level.

Signal-to-noise ratio of a near-infrared static wind imaging Michelson interferometer.

Wind is a key parameter to understand the dynamic behavior of the atmosphere. This paper focuses on the signal-to-noise ratio (SNR) of the near-infrared static wind imaging Michelson interferometer developed by our research group. As a physical quantity related directly to the resolution of airglow radiation, SNR is an important index to evaluate the performance of interferometers. The theoretical model of SNR is derived, and the changing rules of SNR under various physical quantities are given by computer simulation. This research provides a reliable theoretical basis for the design, development, and engineering of novel wind imaging interferometers.

Influence of the tilted arm glass on the temperature and wind velocity inversion for a static wind imaging interferometer

In a static wind imaging Michelson interferometer (SWIMI) developed by us, two-arm glasses are used to achieve the achromatic thermally compensation. The arm glass is cemented with the beam splitter. The tilt of the arm glass would cause a change to the optical path difference (OPD), thereby reducing the visibility of the interferogram and introducing phase error to the SWIMI system, which eventually responsible for errors in the inversion of temperature and wind velocity. In this paper, we present the principle of static wind imaging interferometer and derivate the variation of OPD caused by the two-dimensional tilt of arm glass in detail. By considering a rectangle incident beam, we analyze the effect of arm glass tilt on wind speed and temperature inversion. The results show that in order to realize the wind velocity error less than 3 m/s, the temperature error less than 3 K, and the instrument visibility greater than 0.8, the two-dimensional tilted angle of arm glass should be less than 1”. The tolerance of tilted angle can expand by adjusting the refractive index of the medium on both two sides of the arm glass or by adjusting the reflector mirror of the interferometer precisely. The results would be helpful for the cement of arm glass, beam splitter of SWIMI, and provide a reference for the design of a field-widened wind imaging interferometer.

Design and fabrication of high-performance multimode interferometer in lithium niobate thin film.

We propose and demonstrate a type of high-performance transverse magnetic (TM) multimode interferometer (MMI) in Z-cut thin film lithium niobate (TFLN). Both 1 × 2 and 4 × 4 MMI designs are demonstrated. Simulation results show that the insertion losses (ILs) are nominally about 0.157 and 0.297 dB for the 1 × 2 and 4 × 4 MMI, respectively, with wide fabrication tolerances. Based on the designed structure, the MMIs are fabricated using an argon based induced coupled plasma (ICP) etching method in Z-cut TFLN. The measured ILs are 0.268 and 0.63 dB for these two kinds of devices. The presented TM mode MMI featuring compact size and low loss can be used for both multifunctional devices and on-chip integrated circuits on a Z-cut TFLN platform.

Preliminary simulation analysis of the temperature fluctuation effect on Taiji-1 Laser interferometer

Space-borne gravitational wave detection imposes a demanding requirement on the sensitivity of the laser interferometer. Among all disturbances that affect the measurement accuracy of the laser interferometer, temperature fluctuations contribute significantly. In this paper, the structure model and the interference path design of Taiji-1 laser interferometer have been used to conduct a preliminary simulation analysis of the temperature fluctuation noise through the finite element method. The temperature, the displacement and the optical path difference fluctuations have been obtained and theoretically analyzed. The preliminary simulation results are consistent with the theoretical analysis, which shows that the thermal–structural–optical simulation scheme adopted in this paper is reasonable. With the preliminary simulation results and the actual temperature control of Taiji-1 laser interferometer, we estimate that in Taiji-1 laser interferometer system, the temperature fluctuation is below the order of mK, the node displacement is within [Formula: see text][Formula: see text]pm, and the interference arm length difference fluctuation amplitude of the laser interferometer is also within [Formula: see text][Formula: see text]pm.

Inverse design of a single-frequency diffractive biosensor based on the reporter cleavage detection mechanism.

Vertically interrogated porous silicon (PSi) interferometric biosensors have shown high potential for sensing bio-molecules as they combine high detection sensitivity with simplicity of fabrication, functionalization, optical coupling, and interfacing with microfluidic systems. However, most interferometric sensor designs require either broadband or wavelength-tunable light sources as well as wide-angle detection schemes, increasing their complexity and cost for point-of-care biosensing applications. The limit of detection of such sensors is also constrained by the small size and low refractive index of biological molecules, making it hard to detect very low concentrations of pathogens. In this work, we use a large-scale computational "inverse design" technique to demonstrate a single-frequency, fixed-angle PSi-based biosensor, which exploits a recently developed high-contrast reporter cleavage detection (HCCD) technique. The HCCD sensors detect high-index reporter cleavage events instead of low-index target analyte capture events as typical for traditional label-free optical biosensors. We use the inverse design approach to discover an optimal configuration of a PSi biosensor that makes use of the extended achievable range of cleavage-induced PSi effective index variations and can be interrogated at a single frequency and at a fixed angle. The optimized design in the form of a one-dimensional PSi grating exhibits the change in the reflectance up to 55 % at the interrogation angle of 12∘ and wavelength of 600 nm, which is caused by cleavage of Au nanoparticle reporters initially occupying 2% of the sensor surface area. The maximum possible change in reflectance is predicted to be 222 % (for a two-dimensional freeform design not amenable to fabrication). This demonstration may pave the way for developing new or redesigned conventional interferometric and colorimetric point-of-care biosensor systems in combination with the cleavage-based detection schemes.

Lithography-free and Highly Angle Sensitive Structural Coloration Using Fabry\u2013Perot Resonance of Tin

Recently, there has been much interest in applying the color changes of nano-patterned structures to sensor technology. However, the lithographic nano-patterning process is not environmentally friendly, and it is difficult to fabricate large areas of color due to limitations associated with this approach. In this study, we realized a highly tunable structural coloration based on a Fabry–Perot interferometer design that does not require nano-patterning processes. To increase the reflected color change according to the angle, a color element using an asymmetric metal–insulator–metal structure was applied, fabricated using silver–silicon dioxide–tin (Sn), respectively. Using the optical properties of Sn, we maximized the change in reflection color and realized three primary colors of subtractive color of cyan, magenta and yellow according to the angle of designed MIM structure. Theoretical and experimental results revealed that the color and intensity of the reflectance depended strongly on the angle of the reflective surfaces. The manufacturing process is simple and yields large surfaces of high quality. Based on this premise, we fabricated a soft robot capable of color camouflage, and an angle-detecting color sensor for inspecting the three-dimensional shape quality of curved glass with a high sensitivity of 1.8 nm/degree. In addition, we propose a shape evaluation method by color, spectrometry, and monochromatic light.

Design and Development of Oblique-Incident Interferometer for Form Measurement of Hand-Scraped Surfaces

Design and Development of Oblique-Incident Interferometer for Form Measurement of Hand-Scraped Surfaces

Design of a dispersion interferometer on a field-reversed configuration device.

Dispersion interferometry (DI) is a promising method for density measurement. Compared with the traditional interferometer, the DI is immune to mechanical vibration and can avoid the fringe jump error. In addition, a simple optical configuration is also one of the advantages of the DI. The electron density of the Huazhong University of Science and Technology field-reversed configuration (HFRC) device can reach 1020m-3 with a pulse length of 50 µs. In this case, the DI based on the CO2 laser on the HFRC device adopts the heterodyne technique based on the acousto-optic modulator, which can increase the temporal resolution to 40MHz. It can realize density fluctuation measurements in the MHz range. The test of each optical element, especially the nonlinear crystal, has been completed. The AgGaSe2 crystal can produce a second harmonic wave of about 52.5 µW when the incident CO2 power is 10W. Based on these designs and tests, a DI system can be expected on the HFRC device.

Design of a SOI-based quantum interferometer with ultralow fiber-to-fiber insertion loss

Based on the standard silicon-on-insulator platform, we design an on-chip interferometer at the telecom spectral range, with ultra-low fiber-to-fiber insertion loss. Special attention is given to beams splitters with waveguide tapers instead of single-mode waveguides as input ports. By carefully designing the dimension of the waveguide taper, the multimode mode waveguide and the multi-mode interferometer, the structures can achieve the highest intermode conversion efficiency We numerically demonstrate that the proposed ladder-shaped waveguide taper achieves a high transmission of more than 80%, with an ultra-short length of only 20μm. The total insertion loss from the input fiber to output fiber can be reduced down to 1.07 dB. This work holds a great potential in various application, especially for the on-chip quantum interferometer that highly desires the low-loss property.

High sensitivity X-ray phase contrast imaging by laboratory grating-based interferometry at high Talbot order geometry.

X-ray phase contrast imaging is a powerful analysis technique for materials science and biomedicine. Here, we report on laboratory grating-based X-ray interferometry employing a microfocus X-ray source and a high Talbot order (35th) asymmetric geometry to achieve high angular sensitivity and high spatial resolution X-ray phase contrast imaging in a compact system (total length <1 m). The detection of very small refractive angles (∼50 nrad) at an interferometer design energy of 19 keV was enabled by combining small period X-ray gratings (1.0, 1.5 and 3.0 µm) and a single-photon counting X-ray detector (75 µm pixel size). The performance of the X-ray interferometer was fully characterized in terms of angular sensitivity and spatial resolution. Finally, the potential of laboratory X-ray phase contrast for biomedical imaging is demonstrated by obtaining high resolution X-ray phase tomographies of a mouse embryo embedded in solid paraffin and a formalin-fixed full-thickness sample of human left ventricle in water with a spatial resolution of 21.5 µm.

Piezoelectric mirror shifter transfer function measurement, modelling, and analysis using feedback based synthetic-heterodyne Michelson interferometry

Laser vibrometry has many applications in non-contact dynamic displacement and vibration measurement. A test beam reflected from a target and a reference beam are combined and detected by a photodiode; the photodetected signal is then processed to determine the target displacement and vibration. This paper describes the use of a 9 kHz measurement bandwidth system, consisting of a Michelson interferometer and self-correcting feedback synthetic-heterodyne signal processing technique, to measure the displacement impulse response of a commercial piezoelectric mirror shifter (PMS), consisting of a mirror mounted on a Piezoelectric transducer and a connecting 50 Ω electrical coaxial cable. The actual non-ideal applied impulse and measured impulse response data were used in conjunction with the instrument variable method to determine a Laplace domain linear transfer function approximation to the actual PMS transfer function. The best transfer function fitting, having a 84% normalized root mean square goodness of fit, was obtained using a 5-th order transfer function having two complex conjugate pole pairs, with associated natural frequencies of 6.29 and 6.79 kHz, and a single real pole. The transfer function zeros consisted of a single complex conjugate zero pair, having an antiresonance frequency of 6.38 kHz and a single real zero. Knowing the analytic transfer function of PMS based nanopositioners is useful for example in the design of closed-loop phase-locked interferometers for wideband sensing.

ПАССИВНАЯ СТАБИЛИЗАЦИЯ ИНТЕРФЕРОМЕТРА МАЙКЕЛЬСОНА

In some applications of a Michelson interferometer, in particular, when it is used in a laser resonator, the phase difference of radiation beams passing the interferometer optical branches must be stabilized with high accuracy. The proposed paper is devoted to experimental studying the long-term stability of several interferometer designs and choosing the optimal version for applying as a compound resonator mirror with the controllable reflection for generation of ultrashort laser pulses.

Multi-Parameter Optimization of an InP Electro-Optic Modulator

In this article, a method for indium phosphide (InP) electro-optic modulator (EOM) optimization is introduced. The method can be used for the design and analysis of an EOM based on the Mach-Zehnder interferometer (MZI) design. This design is based on the division of the input optical signal into two optical paths and then, after processing, it combines the light into a single waveguide. The symmetry of the structure can provide state-of-the-art EOM characteristics with a push-pull control signal. Using a traveling wave electrode (TWE) design as a starting point, the authors varied the heterostructure design and optical waveguide parameters to obtain the optimal values of initial optical loss, evenness of the initial optical loss in the operating wavelength range, and the extinction ratio and length of the modulator arm. The key features of the proposed optimization method include the following: all independent input parameters are linked into a single system, where the relationship between the electrical and optical parameters of the modulator is realized; all physically realizable combinations of the input parameters are available for analysis; and EOM optimization is possible for one target parameter or for a group of target parameters. The results of the EOM optimization using the described method are presented.

Tailoring Multiloop Atom Interferometers with Adjustable Momentum Transfer.

Multiloop matter-wave interferometers are essential in quantum sensing to measure the derivatives of physical quantities in time or space. Because multiloop interferometers require multiple reflections, imperfections of the matter-wave mirrors create spurious paths that scramble the signal of interest. Here, we demonstrate a method of adjustable momentum transfer that prevents the recombination of the spurious paths in a double-loop atom interferometer aimed at measuring rotation rates. We experimentally study the recombination condition of the spurious matter waves, which is quantitatively supported by a model accounting for the coherence properties of the atomic source. We finally demonstrate the effectiveness of the method in building a cold-atom gyroscope with a single-shot acceleration sensitivity suppressed by a factor of at least 50. Our study will impact the design of multiloop atom interferometers that measure a single inertial quantity.

A Seismological Study of the Sos Enattos Area—the Sardinia Candidate Site for the Einstein Telescope

AbstractThe recent discovery of gravitational waves (GWs) and their potential for cosmic observations prompted the design of the future third-generation GW interferometers, able to extend the observation distance for sources up to the frontier of the Universe. In particular, the European detector Einstein Telescope (ET) has been proposed to reach peak strain sensitivities of about 3×10−25 Hz−1/2 in the 100 Hz frequency region and to extend the detection band down to 1 Hz. In the bandwidth [1,10] Hz, the seismic ambient noise is expected to represent the major perturbation to interferometric measurements, and the site that will host the future detectors must fulfill stringent requirements on seismic disturbances. In this article, we conduct a seismological study at the Italian ET candidate site, the dismissed mine of Sos Enattos in Sardinia. In the range between few mHz to hundreds of mHz, out of the detection bandwidth for ET, the seismic noise is compatible with the new low-noise model (Peterson, 1993); in the [0.1,1] Hz bandwidth, we found that seismic noise is correlated with sea wave height in the northwestern Mediterranean Sea. In the [1,10] Hz frequency band, noise is mainly due to anthropic activities; within the mine tunnels (≃100 m underground), its spectrum is compliant with the requirements of the ET design. Noise amplitude decay with depth is consistent with a dominance of Rayleigh waves, as suggested by synthetic seismograms calculated for a realistic velocity structure obtained from the inversion of phase- and group-velocity dispersion data from array recording of a mine blasting. Further investigations are planned for a quantitative assessment of the principal noise sources and their spatiotemporal variations.

Design of HCN laser based interferometer on the Space Plasma Environment Research Facility (SPERF)

A single-channel far-infrared (FIR) hydrogen cyanide (HCN) laser interferometer will be constructed aiming to provide the line integrated electron density on the Space Plasma Environment Research Facility (SPERF) . A continuous glow discharge HCN laser with a cavity length of 3 m is used as the laser source with a wavelength of 337 μm and an output power about 10 mW . The interferometer system is a Mach-Zehnder type. The temporal resolution of the system is 0.1 ms since the phase modulation is achieved by a rotating grating with a modulation frequency of 10 kHz. The beat signal is detected by AlGaN/GaN high electron mobility transistors (HEMT) detector. It has a noise equivalent power of 10 pW/Hz−1/2. Excellent port access (1500×150 mm) and high laser power would promise a profile measurement across the whole plasma section with good signal quality. The design and structure of the single-channel FIR HCN laser interferometer in SPERF is described in detail.

Flexible A-scan rate MHz-OCT: efficient computational downscaling by coherent averaging.

In order to realize adjustable A-scan rates of fast optical coherence tomography (OCT) systems, we investigate averaging of OCT image data acquired with a MHz-OCT system based on a Fourier Domain Mode Locked (FDML) laser. Increased system sensitivity and image quality can be achieved with the same system at the cost of lower imaging speed. Effectively, the A-scan rate can be reduced in software by a freely selectable factor. We demonstrate a detailed technical layout of the strategies necessary to achieve efficient coherent averaging. Since there are many new challenges specific to coherent averaging in swept source MHz-OCT, we analyze them point by point and describe the appropriate solutions. We prove that coherent averaging is possible at MHz OCT-speed without special interferometer designs or digital phase stabilization. We find, that in our system up to ∼100x coherent averaging is possible while achieving a sensitivity increase close to the ideal values. This corresponds to a speed reduction from 3.3 MHz to 33 kHz and a sensitivity gain of 20 dB. We show an imaging comparison between coherent and magnitude averaging of a human finger knuckle joint in vivo with 121dB sensitivity for the coherent case. Further, the benefits of computational downscaling in low sensitivity MHz-OCT systems are analyzed.