Michelson Interferometer Research Articles

Six-telescope integrated optics beam combiner fabricated using ultrafast laser inscription for J- and H-band astronomy.

We have built and characterized, to our knowledge, the first six-telescope discrete beam combiner (DBC) for stellar interferometry in the astronomical J-band. It is the DBC with the largest number of beam combinations and was manufactured using ultrafast laser inscription in borosilicate glass, with a throughput of ≈56%. For calibration of the visibility-to-pixel matrix, we use a two-input Michelson interferometer and extract the complex visibility. A visibility amplitude of 1.05 and relative precision of 2.9% and 3.8% are extracted for 1328nm and 1380nm, respectively. Broadband (≤40n m) characterization is affected by dispersion but shows similar performance.

Validation of Version 1.3 Ozone Measured by the SOFIE Instrument

AbstractThe Solar Occultation for Ice Experiment (SOFIE) has operated aboard the Aeronomy of Ice in the Mesosphere (AIM) satellite since 2007. SOFIE uses solar occultation to retrieve ozone (O3) profiles from ∼20 to 100 km altitude, typically at polar latitudes. This study validates SOFIE O3 profiles, including error analysis and comparisons with independent observations. Comparisons are made to the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE‐FTS) and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite instruments. SOFIE shows qualitative and quantitative agreement with both data sets between 30 and 70 km and better overall agreement in the northern hemisphere. SOFIE and ACE mean differences are typically within 20% in the 30–70 km altitude range. SOFIE and MIPAS exhibit mean difference values within 30% in the winter and 20% for all other seasons averaged, between ∼30 and 60 km. Seasonal comparisons indicate similar variations in both hemispheres and through all seasons. The comparisons indicate that SOFIE is biased 5%–10% low at 30–70 km altitudes, with greater differences at higher and lower altitudes. The comparisons are challenging due to the low O3 concentrations at high altitudes, the limited number of coincidences, and the large diurnal variation in mesospheric O3 during twilight hours.

Energetic Electron Precipitation During Slot Region Filling Events

AbstractThe slot region marks the equatorward boundary of the energetic electron precipitation (EEP). There are, however, numerous reports where energetic electrons cross these boundaries and fill the slot region. The ensuing EEP will occur long after the geomagnetic activity subsides. This is a missing energy input in current EEP estimates scaled by geomagnetic indices. This study explores the occurrence rate, duration, and local time dependence of slot region filling events using observations from the National Oceanic and Atmospheric Administration/Polar Orbiting Environmental Satellites over a full solar cycle from 2004 to 2014. The EEP flux estimates are based on the Medium Energy Proton Electron Detector 0° and 90° detectors and the theory of pitch angle diffusion by wave‐particle interaction. The occurrence rates of >43, >114, and >292 keV events are found to be strongly energy and solar cycle dependent. Higher energy events are more likely to be associated with Coronal Mass Ejections and stronger geomagnetic deflections compared to lower energy events. Solar wind speed, Bz, and Ey reveal a calm period before the events, potentially important for preconditioning the ensuing magnetospheric mass convection. The slot region reforms more efficiently closer to the plasmapause, which creates a double EEP band throughout the recovery period. The slot region EEP maximizes around noon throughout the afternoon/evening sector, consistent with pitch angle scattering from plasmaspheric hiss and lightning induced whistler mode waves. Concurrent with slot region filling events, the Michelson Interferometer for Passive Atmospheric Sounding/Envisat nitric oxide density show an increase at <55° corrected geomagnetic latitudes. This demonstrates the importance of including slot region EEP when assessing the EEP impact on the atmosphere.

Modeling multiply scattered light in full-field optical coherence tomographic imaging of biological tissues

In this work, we have constructed a handheld full-field optical coherence tomography (FFOCT) system with high spatial resolution, and the Michelson interferometer (served as compensating optical path) and Fizeau interferometer (served as detection) were mounted in series in this system. The expressions of the multiple scattered light decomposed as the sum of incoherent and coherent contribution were derived based on the diffusion equation and mutual coherence function, and the variations of resolution with imaging depth were derived by using the model of multiple scattering. Experiments were conducted on samples composed of the USAF 1951 resolution target covered by the onion slice and human finger-skin slice, respectively, to validate and evaluate the accuracy of our model. A method of image restoration is then presented in which the relation between the resolution and measuring depth and the simulated PSF in the absence of multiple scattering are employed. With the help of this method the lateral resolution of 2.2 μm and 3.9 μm were separately achieved in the onion slice (measuring depth of 64 μm) and human finger-skin slice (measuring depth of 60 μm), and more tiny structures in the en face image of human finger-skin and moth wings were visible. In addition, a novel method for estimating the values of mean free path and anisotropy of scattering medium was proposed.

Ionosphere-thermosphere coupling via global-scale waves: new insights from two-years of concurrent in situ and remotely-sensed satellite observations

Growing evidence indicates that a selected group of global-scale waves from the lower atmosphere constitute a significant source of ionosphere-thermosphere (IT, 100–600 km) variability. Due to the geometry of the magnetic field lines, this IT coupling occurs mainly at low latitudes (< 30°) and is driven by waves originating in the tropical troposphere such as the diurnal eastward propagating tide with zonal wave number s = −3 (DE3) and the quasi-3-day ultra-fast Kelvin wave with s = −1 (UFKW1). In this work, over 2 years of simultaneous in situ ion densities from Ion Velocity Meters (IVMs) onboard the Ionospheric Connection Explorer (ICON) near 590 km and the Scintillation Observations and Response of the Ionosphere to Electrodynamics (SORTIE) CubeSat near 420 km, along with remotely-sensed lower (ca. 105 km) and middle (ca. 220 km) thermospheric horizontal winds from ICON’s Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) are employed to demonstrate a rich spectrum of waves coupling these IT regions. Strong DE3 and UFKW1 topside ionospheric variations are traced to lower thermospheric zonal winds, while large diurnal s = 2 (DW2) and zonally symmetric (D0) variations are traced to middle thermospheric winds generated in situ. Analyses of diurnal tides from the Climatological Tidal Model of the Thermosphere (CTMT) reveal general agreement near 105 km, with larger discrepancies near 220 km due to in situ tidal generation not captured by CTMT. This study highlights the utility of simultaneous satellite measurements for studies of IT coupling via global-scale waves.

Polarizing white light interferometry for phase measurements using two simultaneous interferograms.

Our research introduces a design for a polarization phase-shifting white light interferometric system (PPS-WLIS) that operates in a transmissive mode for measuring the slope phase of transparent objects. It comprises a cyclic path interferometer (lateral shear interferometer) coupled with a multiplexing Michelson interferometer. The system uses polarization to produce two parallel interferograms with polarization modulated with relative shifts simultaneously. To determine the optical phase, we used a two-step algorithm for phase demodulation that does not necessitate precise phase shifts, making the system more straightforward to operate. As a result, we could observe variations in the object associated with optical phase changes. Furthermore, our method simplifies the phase-shift interferometry process by requiring only one capture, making it an effective way to examine objects at dynamic events. As an illustration, we demonstrated the temperature measurement generated by a section of a candle flame.

Delta interferometer: A polarization sensitive interferometer

Abstract A new type of polarization sensitive interferometer is proposed, which is named as Delta interferometer due to the geometry of the simplest interferometer of this type looks like Greek letter, Delta. The main difference between Delta interferometer and other existed interferometer, such as Michelson interferometer, Mach-Zehnder interferometer, Young’s double-slit interferometer, is that the two interfering paths are asymmetrical in Delta interferometer. The visibility of the first-order interference pattern observed in Delta interferometer is dependent on the polarization of the incidental light. Optical coherence theory is employed to interpret the phenomenon and single-mode continuous-wave laser light is employed to verify the theoretical predictions. The theoretical and experimental results are consistent. Delta interferometer provides a perfect tool to study the reflection of electromagnetic field in different polarizations and may find applications in polarization sensitive scenarios.

A relative humidity sensor based on 2-core fiber Michelson interferometer with end-face aluminium mirror

A relative humidity sensor based on 2-core fiber Michelson interferometer with end-face aluminium mirror

New electronic implementation of the timestamps method intended for high resolution comparison of laser wavelengths.

This article describes a new measurement system for the comparison of two electronic signals of different frequencies with application to high resolution comparison of laser wavelengths using a Michelson interferometer. It was built within the framework of research projects made by the University of Vigo and the Laboratorio Oficial de Metroloxía de Galicia (LOMG) in cooperation with Escolas Proval High School. The new hardware is based on a cheap high-speed module for the acquisition of data and a microcontroller module for processing, which can also be used for practical lessons in vocational training. The system has been tested with electronic signal generators. The novel measurement method reduces the uncertainty using multiple consecutive measurements and the fractional part of the fringes and could achieve precisions in the range 10-12 of the wavelength ratios.

Direct determination of 2D momentum space from 2D spatial coherence of light using a modified Michelson interferometer.

Momentum space distribution of photons coming out of any light emitting material/device provides critical information about their underlying physical origin. Conventional methods of determining such properties impose specific instrumentational difficulties for probing samples kept within a low temperature cryostat. There were past studies to measure a one-dimensional coherence function, which could then be used for extracting momentum space information, as well as reports of measurements of just a two-dimensional (2D) coherence function. However, all of those are associated with additional experimental complexities. So, here we propose a simpler, modified Michelson interferometer based optical setup that is kept at room temperature and placed outside the low temperature cryostat at a distance away from it. We initially measure the 2D coherence function of emitted light, which can then be used to directly estimate the 2D in-plane momentum space distribution by calculating its fast Fourier transform. We also discuss how this experimental method can overcome instrumentational difficulties encountered in the past. Similar instrumentations can also be extended for momentum space resolved astronomical studies and telecommunications involving distant light sources.

UV femtosecond single-pulse and collinear double-pulse laser-induced breakdown spectroscopy (LIBS) for depth-resolved characterization of nano-scaled films

In the current work, we demonstrate the UV femtosecond (248 nm, 450 fs) single-pulse and double-pulse laser-induced breakdown spectroscopy (LIBS) as an effective method for depth profiling of nanometer-thick multi-layered structures, including photovoltaic thin films. Femtosecond LIBS enabled selective detection of both organic and inorganic materials at different depths within nanometer-scale (10–250 nm) multi-layered samples having thicknesses comparable to the etching depth produced by a single laser shot ablation. To enhance the analytical capabilities of the method, we applied the collinear double-pulse LIBS technique, using a Michelson interferometer to split the laser pulse into two equal-energy pulses. Results obtained with Indium Tin Oxide (ITO) nanofilms (115 nm layer thickness) present a clear increase of the intensity emission by a factor of 3 to 10, depending on laser fluence, when the double-pulse approach is used. Single-pulse LIBS achieved an ablation rate of around 60 nm, while the double-pulse configuration achieved 40 nm/pulse, in a sequence of seven laser shots. Furthermore, via double-pulse LIBS spectra were recorded even at fluences as low as 150 mJ/cm2, compared to 250 mJ/cm2 required for capturing spectra, when the same total energy per pulse was maintained.

A Geometric Analysis of Relativity

Relativity’s mathematical models are based upon the MichelsonMorley Interferometer Experiment of 1887. Wikipedia provides an illustration of the interferometer and a description of the experiment: A ray of light traveling at velocity, c, was reflected from one mirror to another at a distance, L (the length of the interferometer arms), in an attempt to measure movement of the earth relative to light, v.

Nonlinearities in Fringe-Counting Compact Michelson Interferometers.

Compact Michelson interferometers are well positioned to replace existing displacement sensors in the readout of seismometers and suspension systems, such as those used in contemporary gravitational-wave detectors. Here, we continue our previous investigation of a customised compact displacement sensor built by SmarAct that operates on the principle of deep frequency modulation. The focus of this paper is the linearity of this device and its subsequent impact on sensitivity. We show the three primary sources of nonlinearity that arise in the sensor: residual ellipticity, intrinsic distortion of the Lissajous figure, and distortion caused by exceeding the velocity limit imposed by the demodulation algorithm. We verify the theoretical models through an experimental demonstration, where we show the detrimental impact that these nonlinear effects have on device sensitivity. Finally, we simulate the effect that these nonlinearities are likely to have if implemented in the readout of the Advanced LIGO suspensions and show that the noise from nonlinearities should not dominate across the key sub-10 Hz frequency band.

A new Einstein coefficient method for mesopause-lower thermosphere atmosphere temperature retrieval under a non-local thermal equilibrium situation.

The mesopause-lower thermosphere (MLT) region is an important spatial region in the Earth's atmosphere, making it a valuable area to investigate the temperature variations. Kirchhoff's law fails with the altitude increase due to the non-local thermal equilibrium effect, resulting in an increase in the error of the method to retrieve the atmospheric temperature in the MLT region using the A-band spectral line intensity. In the non-LTE state, the temperature retrieval method based on the Einstein coefficients is proposed to retrieve atmospheric temperature in the 92-140 km height range using the airglow radiation intensity images obtained from the Michelson Interferometer for global high-resolution thermospheric imaging (MIGHTI) measurements. Results show that the temperature deviation of the two-channel combinations does not exceed 15 K in the altitude range of 92-120 km. This deviation increases up to 45 K when the altitude is in the range of 120-140 km due to the influence of the N2 airglow spectrum. The two-channel combinations self-consistency is increased by 85 K compared with the temperature obtained using the spectral line intensity retrieval. Additionally, the comparison of the retrieval results with the spectral line intensity method and the comparison with the atmospheric chemistry experiment Fourier transform spectrometer (ACE-FTS) temperature measurement data shows that the Einstein coefficient method is significantly more rational and accurate than the spectral line intensity method.

Noise robust Zernike phase retrieval via learning based algorithm only with 2-step phase shift measurements.

We present a noise robust deep learning based aberration analysis method using 2-step phase shift measurement data. We first propose a realistic aberration pattern generation method to synthesize a sufficient amount of real-world-like aberration patterns for training a deep neural network by exploiting the asymptotic statistical distribution parameters of the real-world Zernike coefficients extracted from a finite number of experimentally measured real-world aberration patterns. As a result, we generate a real-world-like synthetic dataset of 200,000 different aberrations from 15 sets of real-world aberration patterns obtained by a Michelson interferometer under a variety of measurement conditions using the 4-step derivative fitting method together with the exploitation of the Gaussian density estimation. We then train the deep neural network with the real-world-like synthetic dataset, using two types of network architectures, GoogLeNet and ResNet101. By applying the proposed learning based 2-step aberration analysis method to the analysis of numerically generated aberrations formed under 100 different conditions, we verify that the proposed 2-step method can clearly outperform the existing 4-step iterative methods based on 4-step measurements, including the derivative fitting, transport of intensity equation (TIE), and robust TIE methods, in terms of noise robustness, root mean square error (RMSE), and inference time. By applying the proposed 2-step method to the analysis of the real-world aberrations experimentally obtained under a variety of measurement conditions, we also verify that the proposed 2-step method achieves compatible performance in terms of the RMSE between the reconstructed and measured aberration patterns, and also exhibits qualitative superiority in terms of reconstructing more realistic fringe patterns and phase distributions compared to the existing 4-step iterative methods. Since the proposed 2-step method can be extended to an even more general analysis of aberrations of any higher order, we expect that it will be able to provide a practical way for comprehensive aberration analysis and that further studies will extend its usefulness and improve its operational performance in terms of algorithm compactness, noise robustness, and computational speed.

Sagnac interferometer based optical coherence tomography

We present in this paper an all-fiber Optical Coherence Tomography OCT system in the time domain by employing a Sagnac fiber loop. The optical fiber version of TD-OCT uses directional couplers to construct a Michelson interferometer instead of a beam splitter which is used in the bulk optics version. Instead of implementing the optical delay by an external movable mirror, we present a new configuration that employs a Sagnac interferometer. Avoiding the use of an external movable mirror, eliminates the problems of alignment to couple back the optical signal into the fiber after being delayed by the external mirror. Moreover, this all-fiber system has the advantage of being compact and having large values of optical path difference.

Static wind imaging Michelson interferometer for the measurement of stratospheric wind fields.

The stratospheric wind field provides significant information on the dynamics, constituent, and energy transport in the Earth's atmosphere. The measurement of the atmospheric wind field on a global basis at these heights is still lacking because few wind imaging interferometers have been developed that can measure wind in this region. In this paper, we describe an advanced compact static wind imaging Michelson interferometer (SWIMI) developed to measure the stratospheric wind field using near-infrared airglow emissions. The instrument contains a field widened and thermal compensated interferometer with a segmented reflective mirror in one arm, which replace the moving mirror in a conventional Michelson interferometer, to provide interference phase steps. The field widened, achromatic, temperature compensated scheme has been designed and manufactured. The characterization, calibration, inversion software, and test of the instrument have been completed. The capacity of two-dimensional wind, temperature, and ozone measurement of the instrument has been verified in the lab experiment and model simulation. What we believe to be the novel principle, modeling, design, and experiment demonstrated in this paper will offer a significant reference to the static, simultaneous and real-time detection and inversion of the global wind field, temperature, and ozone.

Accessible interferometric autocorrelator for noise-like pulses based on a Fabry-Perot cavity.

In this work, we develop experimentally a Fabry-Perot fiber optic interferometer applied to the measurement of autocorrelation of complex dynamic pulses generated by a figure-eight fiber laser. The principle is based in the superposition of multiple pulses, which requires two partially reflecting flat surfaces in parallel, resulting in a simple and compact autocorrelator design. The autocorrelation trace obtained exhibits a typical double-scaled structure for noise-like pulses (NLPs), with an ultrashort coherence spur on the order of 100 fs riding upon a broad pedestal of 120 ps. Finally, we show experimentally that the developed Fabry-Perot device is able to measure accurately the autocorrelation of NLPs, as confirmed by comparing the measurement with that of a conventional autocorrelator scheme based on a Michelson interferometer, with the additional advantages of a more compact setup and a much easier alignment procedure compared to the latter.

Enhanced resolution of edge enhancement in three-dimensional vortex imaging based on a modified Michelson interferometer

Edge enhancement is emerging as an essential technique for object recognition in recent years. The edge detection of three-dimensional (3D) imaging has been successfully demonstrated in Fresnel incoherent correlation holograph (FINCH) system; however, with a relatively low resolution which needs to be further improved to meet practical requirements. In this work, a modified Michelson interferometer system using a spatial light modulator (SLM) is proposed, which realizes 3D vortex imaging with high resolution and low background noise. Compared with the spiral phase modulated polarization multiplexing FINCH system, the resolution of this system has apparently improved from 50.80 lp mm−1 to 57.02 lp mm−1. The improvement is assumed to be ascribed to the inherently high luminous flux utilization configuration of the Michelson interferometer and the precision phase shifts. More importantly, the proposed system exhibits prominently improved performance of edge enhancement for different objects, including the standard resolution target and label-free biological living cells. The experimental results of the small watch parts also demonstrate its ability in 3D vortex imaging with edge detection. These results provide a promising strategy for high-quality 3D vortex imaging and edge enhancement, and might pave the way for future applications in the fields such as edge detection and pattern recognition.

Broadband dispersion spectroscopy using interferometric phase modulation under background light suppression.

This Letter presents a dispersion spectroscopy method that achieves simultaneous detection of molecular vibrational dispersion over a broad spectral range. The method is implemented with an infrared mode-locked laser, a dispersion-compensated Michelson interferometer, and a multichannel detector. Synchronous detection under interferometric phase modulation near the destructive interference condition is employed to achieve a high signal-to-noise ratio. We successfully demonstrate the method by measuring the dispersion of carbon monoxide gas, achieving a noise-equivalent dispersion of 1.3 × 10-8 cm and a corresponding noise-equivalent absorbance of 6.5 × 10-4 with a measurement time of 2.2 s.