Corner Cube Reflector Research Articles

Self-referenced prism deflection measurement schemes with microradian precision

We have demonstrated several inexpensive methods that can be used to measure the deflection angles of prisms with microradian precision. The methods are self-referenced, where various reversals are used to achieve absolute measurements without the need of a reference prism or any expensive precision components other than the prisms under test. These techniques are based on laser interferometry and have been used in our laboratory to characterize parallel-plate beam splitters, penta prisms, right-angle prisms, and corner cube reflectors using only components typically available in an optics laboratory.

Simulation of environment effects on retroreflectors in ITER

Two plasma diagnostics in ITER will use cube-corner reflectors (CCR): poloidal polarimetry and toroidal interferometry/polarimetry. The multichannel poloidal polarimetry system is planned to operate at a wavelength of 118.8μm. The multichannel toroidal interferometry/polarimetry system is based on a CO2 laser operating at wavelengths of 10.6 and 9.27μm. The long term sputtering by charge exchange atoms and/or deposition of carbon-based (or beryllium-based) contaminant layers can affect the optical properties of the CCR. The role of both these potentially deleterious effects on the CCR operation is analyzed in this article, taking into account the probing beam wavelength and the CCR locations. The conclusion is that for the intended use of a CCR in the poloidal polarimetry at 118μm neither erosion nor deposition should pose a problem. On the other hand, in the toroidal interferometry/polarimetry system operating at 10μm, care must be taken to reduce the charge exchange atom flux and it is likely that deposition will occur and could have deleterious effects especially on the polarization properties of the reflected radiation.

Free-space optical link by microelectromechanical system array and corner cube reflector

We show here a laboratory demonstration of a free-space optical retrocommunication link using a laser at a wavelength of 1.064 μm. The link consists of a transmissive mechanically active antireflection switch array and a corner cube reflector. This link is 3 m long and the beam diameter at the chip is 1.5 mm. A 40% modulation has been achieved at 30-V peak-to-peak bias for a data rate of 2.5 kb/s in atmosphere. We have previously shown that the small etchant hole in the membrane causes a slower data rate, which can be fixed by operating the device in a rough vacuum.

Design, fabrication and test of self-assembled optical corner cube reflectors

Active and passive micromachined corner cube reflectors (CCRs) with high surface flatness and precise assembly are demonstrated by out-of-plane rotation of bonded silicon parts powered by the surface tension of thick photoresist pads. A two-mask fabrication process is used, and an angular alignment accuracy of <0.18° is achieved by minimizing the number of movable parts and controlling the assembly with mechanical limiters. Active CCRs based on torsion mirror scanners with a Q-factor of 20 are demonstrated. When used as a retroreflection data transmitter, a data rate of up to 200 bit s−1 and a signal-to-noise ratio of 30 dB are obtained with a drive voltage of 30 V.

LAGEOS asymmetric reflectivity and corner cube reflectors

Accurate laser tracking of LAGEOS satellites, allows investigation together with gravitational effects, a number of fine nongravitational perturbations in their orbit. Several of these forces are reasonably interpreted in terms of known physical phenomena. Postulated asymmetry in reflectivity of LAGEOS hemispheres is an exception. Here we show that in spite of a recent suggestion, this empirical effect cannot be explained by differential sunlight reflection on germanium and fused silica corner cube reflectors. The true nature of this effect remains puzzling.

Stokes polarization vector and Mueller matrix for a corner-cube reflector

The polarization states of corner cubes (for both uncoated and metal-coated surfaces) have been investigated. The Stokes vector representation has been used to derive compact and concise expressions for the vectors, and also in deriving the Mueller matrices of the corner-cube reflector. Experiments have been performed to verify the theory. Various polarization modes are explored including methods for 100% conversion of (1) circularly polarized light into temporally coherent depolarized light, (2) elliptically polarized light into linearly polarized light, and (3) preserving input/output polarization of circularly polarized light and linearly polarized light.

Pulse Sensing of a Forest Canopy

Results of experimental investigations into the effects arising in the detection and ranging of the earth's forest cover with the use of pulse ultrabroadband radio-frequency radiation are described. A narrow-beam transmitting and receiving antennas oriented at a sliding angle to the forest canopy were mounted on a special mast at an altitude of 21 m above the ground. A corner-cube reflector was used to align and to calibrate the measurement system. The results obtained are compared with the data of independent biometric measurements.

Quasi-optical highly sensitive Schottky-barrier detector for a wide-band FIR FEL

A wide-band FIR detector based on the Schottky-barrier diode for the use on a far-infrared FEL facility has been developed. The detector consists of a GaAs chip with diodes of sub-micrometer diameters and a traveling-wave antenna in a 90° corner-cube reflector that provided effective transmission of the FIR power to the diode from the input FIR focusing lens. The antenna has been optimized for a wavelength of 337μm. At this wavelength, the detector has a sensitivity of 200V/W and a noise equivalent power (NEP) of 0.1nW/Hz1/2. These measurements were made by a HCN laser. For a radiation wavelength of 119μm (H2O laser) the sensitivity and NEP values were measured to be 20V/W and 1.0nW/Hz1/2, respectively. The results of measurements from the compact wide-band FIR FEL facility by the detector in a wide wavelength range are presented. The potentialities of the detector are investigated.

Laser reflector arrangement on H2A-lRE satellite for monitoring spin rate and optical degradation.

We devised a unique array of cube-corner reflectors on a spherical satellite so that laser ranging could be used to detect the spin rate and the optical degradation. On the H2A-LRE satellite, there are reflectors made of synthetic silica and ones made of BK7 glass. We report that the degradation of the BK7 reflectors, as well as the spin rate of the satellite, can be monitored through a spectral analysis of laser-ranging data. The center-of-mass correction of the Laser Ranging Equipment satellite was calculated at 210 +/- 10 mm for all possible systems and throughout the degradation process of the BK7 reflectors.

Millimeter-wave radar sensing of airborne chemicals

This paper discusses the development of a millimeter-wave radar chemical sensor for applications in environmental monitoring and arms-control treaty verification. The purpose of this paper is to investigate the use of fingerprint-type molecular rotational signatures in the millimeter-wave spectrum to sense airborne chemicals. The millimeter-wave sensor, operating in the frequency range of 225-315 GHz, can work under all weather conditions and in smoky and dusty environments. The basic configuration of the millimeter-wave sensor is a monostatic swept-frequency radar that consists of a millimeter-wave sweeper, a hot-electron bolometer or Schottky barrier detector, and a corner-cube reflector. The chemical plume to be detected is situated between the transmitter/detector and reflector. Millimeter-wave absorption spectra of chemicals in the plume are determined by measuring the swept-frequency radar return signals with and without the plume in the beam path. The problem of pressure broadening, which hampered open-path spectroscopy in the past, has been mitigated in this paper by designing a fast sweeping source over a broad frequency range. The heart of the system is a backward-wave oscillator (BWO) tube that can be tuned over 220-350 GHz. Using the BWO tube, we built a millimeter-wave radar system and field-tested it at the Department of Energy Nevada Test Site, Frenchman Flat, near Mercury, NV, at a standoff distance of 60 m, The millimeter-wave system detected chemical plumes very well; detection sensitivity for polar molecules such as methylchloride was down to 12 ppm for a 4-m two-way pathlength.

Glonass Laser Ranging Accuracy With Satellite Signature Effect

GLONASS satellites have been tracked by the worldwide laser ranging networkas well as by the GLONASS-borne microwave-based technique. Owing to thelarge size of their corner cube reflector arrays, the amount of ranging data is enough to determine their orbits from laser ranging data alone. We found, however, that the large size of the array affected the accuracy of measurement to an extent that is dependent on the characteristics of the ranging systems. An azimuthal variation of the reflector array response was also detected in observations from single-photon laser ranging. Orbital analysis reveals that the effect makes the measured range on average 22 mm shorter than expected in the absence of the large array, which explains more than half of the offset of 39 mm previously discovered between microwave and laser orbits.

The lunar laser ranging: operation and science

The advent of optical range measurements on the Moon was made possible 30 years ago with the direct exploration of the Moon with manned or automatic missions which placed several arrays of corner cube reflectors on the lunar surface. Over the last thirty years the precision has regularly improved from the ∼0.25 m range in 1970 to an internal precision of the order of one centimeter today and a post-fit accuracy of 3 cm . The principles are summarized in a first part of the paper, followed by an estimate of the error budget. Statistics of the data produced are then given and show the major role fulfilled today by the French station. A section is devoted to the data analysis together with a summary of the major scientific results obtained in selenodesy and fundamental physics. New prospects are opened with a discussion of the the possibility of ranging more efficiently with transponders on the Moon.

Spin motion of the AJISAI satellite derived from spectral analysis of laser ranging data

The spin rate of the geodetic satellite AJISAI was derived through a spectral analysis of laser range data obtained by precise high-return-rate tracking stations. This new analysis method utilizes the directional dependence of the target optical depth resulting from the sparse distribution of corner cube reflectors on the satellite surface. The third and sixth harmonics of the spin rate were found to be dominant in the pass-by-pass spectral analysis of the full-rate range residuals from multiphoton laser ranging systems. Accumulating hundreds of passes, the analysis results gave the slowdown of AJISAI's spinning from 1997 to 1998. Its trend was almost identical to the conventional flash observation. Although the spin rate derived from this method was not as precise as the conventional one, it can provide global spatial coverage and continuous time coverage to monitor the spin motion. This is a new approach to research satellite orientation and orbit and is applicable to other satellites.

Free space communication link using a grating light modulator

This paper presents the design and operation of a free space communication link based on a grating light modulator (GLM) in a corner cube reflector configuration. A GLM is a micromachined optical phase grating whose grating efficiency can be controlled electrostatically. Combining the GLM with a corner cube to create a grating corner cube (GCC) modulator reduces the alignment requirements of the device. Our device has a measured acceptance angle of ≈6° in the plane of incidence of the GLM, limited by angle dependence of the grating. Significant improvement of the acceptance angle can be achieved by optimizing the layer thickness of the grating structure. The resonance frequency of our GLMs is 290 kHz. Their low damping leads to ringing that increases the switching time to 35 us. The ringing has been reduced using a pre-shaped actuation signal yielding switching times of 10 μs. Low misalignment sensitivity, low power consumption, and low switching times make the GCC ideal for use in free space optical communication links.

Assembly of micro-optical devices using magnetic actuation

We report a high-yield and high-efficiency assembly technique for three-dimensional micro-optical components, including Fresnel lenses, optical gratings, and corner cube reflectors. The three-dimensional assembly process and the optical performance of the assembled components is presented. The angular displacement of individual microstructures is controlled by varying the volume of the magnetic material and through the addition of a flexural-beam loading mechanism to the hinged microstructure. The normal force caused by the deflection of the beam enhances the stability of these devices after they are assembled. The stability of the corner cube reflector is further enhanced by a hooking mechanism in the microstructure. Tests conducted with a He–Ne laser confirm that the measured performance of the Fresnel lens and optical grating correlate well to the expected theoretical values. We also demonstrate the capability for parallel actuation of large arrays of optical components under a global (wafer scale) external magnetic field.

The HG5 laser interferometer mercury manometer of the IMGC

Mercury manometers have been designed and constructed at the Istituto di Metrologia "G. Colonnetti" (IMGC) since 1986, their main characteristic being the adoption of cube-corner reflectors, carried by lightweight floats, to reflect the beams of a laser interferometer that measures the vertical separation between the two mercury menisci. The paper describes the most recent instrument, designated HG5, designed to measure up to 120 kPa in either absolute or relative mode. The major improvements introduced in HG5 over its prototype (HG-3) are: the adoption of larger-bore columns; the installation of a single-beam laser interferometer that allows the use of smaller and less intrusive reflecting floats; the improvement of temperature control and measurement; and the development of cat's-eye floats of a novel design allowing the direct reflection of laser beams on mercury menisci. The uncertainty budget and the equations giving the HG5 standard uncertainties (43 mPa to 314 mPa) under all conditions are included.

Millimeter-wave characteristics of fallen snow

This paper describes the measured 50- to 75-GHz band refractive index, complex dielectric constant, and penetration depth of fallen snow (fresh and corn snow) in the suburbs of Eniwa City in Hokkaido, Japan, calculated from the propagation delay time and loss measured through the sampled naturally piled snows, in order to apply millimeter waves to road traffic control safety and detection of buried materials or road signs in/under the fallen snow. We show that the real part of the dielectric constant depends linearly on snow density, and the penetration depth of corn snow is much smaller than that of ice and fresh snow, after statistically evaluating data measured in different directions and in different parts of the samples. We also describe the experimental difficulty of detecting three types of metals buried in naturally piled 30-mm-thick packed snow and in 50-mm-thick fresh snow (buried corner-cube reflector). © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 82(4): 33–44, 1999

An interferometric device for precise thermal expansion measurements on bar-shaped materials

This design note describes a special device for dilatometric measurements on bar-shaped materials (length standards in particular). The main part of the device is a new Fizeau-type interferometer with two cube-corner reflectors. The test piece is placed between these reflectors, inside a thermostatically controlled box. Its thermal expansion coefficients are measured completely automatically. Measurement results obtained on various materials and length standards are presented. The overall uncertainty for measurements of bars 1 m in length amounts to less than .

Japanese contribution to ITER task of irradiation tests on diagnostics components

Abstract As an R&D task of the ITER engineering design activities (EDA), we carried out the irradiation tests on the basic materials of transmission components such as ceramics, windows, fiber optics and mirrors, and in-vessel diagnostics sensors such as magnetic probes and bolometers. Ceramics will be used as general insulating materials. Here we investigated the radiation induced conductivity (RIC) of ceramics for 14 MeV neutrons. Optical elements are the most sensitive to radiation damages among the transmission components. Radiation induce transmission loss of window materials and fiber optics have been measured in the Japan material testing reactor (JMTR). Off line irradiation tests were carried out for molybdenum corner cube reflector (CCR) and gold coated mirrors in JMTR also. Fourteen MeV-neutron-induce luminescence of window material was evaluated in the fusion neutronics source (FNS). Bolometers should be installed inside the vacuum vessel to measure the radiation losses in the infra red to soft X-ray range. We demonstrated the performance of the JT 60 type bolometer under 60Co gamma-rays.

Automated assembly of flip-up micromirrors

Batch fabrication of microelectromechanical systems utilizing flip-up microstructures is limited by the manual assembly process required to lift the structures off the substrate. This problem is solved with the use of an automated assembly system integrated on the die with the flipup structures. A microelectromechanical automated assembly system consisting of a vertical thermal actuator, a linear assembly micromotor, and a self-engaging locking mechanism is presented in this paper. The vertical thermal actuator is used to lift one end of the plate off the substrate. This provides the linear assembly micromotor with the leverage needed to push the plate up into a position where the self-engaging locking mechanism secures the plate. A CMOS drive system has been developed to control the automated assembly system. When combined with the automated assembly system, CMOS control allows flip-up microstructures to be assembled without any operator intervention. The automated assembly system is demonstrated with a scanning micromirror and a corner cube reflector.