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Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

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Early Posting

Accepted papers to appear in an upcoming issue

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December


Effect of soil temperature on one-way optical frequency transfer through dense-wavelength-division-multiplexing fibre links

  • Tjeerd Pinkert, O. Böll, Lorenz Willmann, G.S.M. Jansen, E. A. Dijck, R. Smets, F. C. Bosveld, Wim Ubachs, Klaus Jungmann, Kjeld Eikema, Jeroen Koelemeij, and B.G.H.M. Groeneveld
  • received 10/17/2014; accepted 12/11/2014; posted 12/12/2014; Doc. ID 225128
  • [full text: PDF (1420) KB)]
  • Abstract: Results of optical frequency transfer over a carrier-grade dense-wavelength-division-multiplexing (DWDM) optical fibre network are presented. The relation between soil temperature changes on a buried optical fibre and frequency changes of an optical carrier through the fibre is modelled. Soil temperatures, measured at various depths by the Royal Netherlands Meteorology Institute (KNMI) are compared with observed frequency variations through this model. A comparison of a nine-day record of optical frequency measurements through the 2 x 298 km fibre link with soil temperature data shows qualitative agreement. A soil temperature model is used to predict the link stability over longer periods (days-months-years). We show that one-way optical frequency dissemination is sufficiently stable to distribute and compare e.g. rubidium frequency standards over standard DWDM optical fibre networks.

Keywords (OCIS):

  • (060.2300) Fiber optics and optical communications : Fiber measurements
  • (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
  • (120.5050) Instrumentation, measurement, and metrology : Phase measurement
  • (120.6810) Instrumentation, measurement, and metrology : Thermal effects

Extraction of optical constants from maxima of fringing reflectance spectra

  • Shun-Tung Yen and Pei-Kang Chung
  • received 10/24/2014; accepted 12/11/2014; posted 12/12/2014; Doc. ID 225686
  • [full text: PDF (408) KB)]
  • Abstract: We propose a scheme to extract the refractive index and the extinction coefficient of dielectrics. The extraction needs only a reflectance spectrum with reliable successive maxima of fringing oscillations measured from a dielectric film either free-standing or on metal. With the film thickness known in advance, we determine the refractive index spectrum from the fringing oscillation periods and then the extinction coefficient spectrum from the upper envelope. The method is demonstrated to work well for GaAs and Ge.

Keywords (OCIS):

  • (120.2230) Instrumentation, measurement, and metrology : Fabry-Perot
  • (120.2650) Instrumentation, measurement, and metrology : Fringe analysis
  • (120.4530) Instrumentation, measurement, and metrology : Optical constants
  • (120.5700) Instrumentation, measurement, and metrology : Reflection
  • (300.6270) Spectroscopy : Spectroscopy, far infrared
  • (300.6470) Spectroscopy : Spectroscopy, semiconductors

4kW Peak Power, Eye-safe All-Fiber MOPA Employing Yb-free Er-doped fiber

  • Kai Guo, Xiaolin Wang, Pu Zhou, and Bohong Shu
  • received 09/22/2014; accepted 12/10/2014; posted 12/12/2014; Doc. ID 223134
  • [full text: PDF (753) KB)]
  • Abstract: In this paper, we reported a master-oscillator power-amplifier (MOPA) operating at eye-safe wavelength 1565nm by two stages structure. A modulated narrow-bandwidth semiconductor laser diode (LD) with 100 kHz repetition and 15ns pulse-width was used as the seed source. Then the average output power was amplified to 6.79W with a peak power of 4.12kW by a double cladding Er-doped fiber (EDCF). Employing the pure Yb-free Er-doped fibers, few 1μm ASE could be observed in the amplifier which was attractive in low repetition pulse laser condition.

Keywords (OCIS):

  • (140.3280) Lasers and laser optics : Laser amplifiers
  • (140.3480) Lasers and laser optics : Lasers, diode-pumped
  • (140.3500) Lasers and laser optics : Lasers, erbium
  • (140.3510) Lasers and laser optics : Lasers, fiber
  • (140.3538) Lasers and laser optics : Lasers, pulsed

Demonstration of Multi-wavelength tunable fiber lasers based on a DMD processor

  • xiao Chen, Qi Ai, Miao Tian, Binbin Yan, Ying Zhang, Fei-Jun Song, Genxiang Chen, Xinzhu Sang, yi Wang, Feng Xiao, and Kamal Alameh
  • received 10/09/2014; accepted 12/10/2014; posted 12/12/2014; Doc. ID 224159
  • [full text: PDF (561) KB)]
  • Abstract: Based on a digital micromirror device (DMD) processor as the multi-wavelength tunable filter, we demonstrate a multi-port tunable fiber laser by experiment. The key property of this laser is any lasing wavelength channel from any arbitrary output-port can be switched independently over the whole C-band, which is only driven by a single DMD chip flexibly. All outputs display an excellent tuning capacity and high consistency in the whole C-band with the line-width 0.02nm, the tuning resolution 0.055nm and side mode suppression ratio greater than 60dB. Due to the automatic power control and polarization design, the power uniformity of output laser is less than 0.008dB and the wavelength fluctuation is below 0.02nm within 2 hours at room temperature.

Keywords (OCIS):

  • (060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators
  • (140.3510) Lasers and laser optics : Lasers, fiber
  • (140.3600) Lasers and laser optics : Lasers, tunable

Interference Effect from Noise on Range-gated Laser Ranging and Tracking System

  • Pengfei Du, Wei Wang, Gan Gao, Yuan Qiu, Mali Gong, and Dongxian Geng
  • received 08/19/2014; accepted 12/10/2014; posted 12/12/2014; Doc. ID 221098
  • [full text: PDF (620) KB)]
  • Abstract: Influence of high-repetition-rate noise on range-gated laser ranging and tracking system (LRTS) is studied both theoretically and experimentally. The interference mechanism of high-repetition-rate noise on range gates is revealed. The interference effect, especially the effect caused by relative shift between signal and noise, is presented through theoretical analysis and numerical simulation. In order to verify the simulation model, both electrical-closed-circuit experiment and optical-circuit experiment are further conducted. Both the simulation model and experiment results show that noise pulses can enter range gates of LRTS and affects its operation with both their high repetition rate and relative shift to echo pulses.

Keywords (OCIS):

  • (250.3140) Optoelectronics : Integrated optoelectronic circuits
  • (280.3400) Remote sensing and sensors : Laser range finder
  • (250.4745) Optoelectronics : Optical processing devices

Polarimetric characterization of birefringent filter components

  • Jason Mudge, Keith Mitchell, and Theodore Tarbell
  • received 10/29/2014; accepted 12/09/2014; posted 12/12/2014; Doc. ID 225955
  • [full text: PDF (536) KB)]
  • Abstract: Over the past 75 years, birefringent filter technology has evolved significantly. For nearly that same period of time, these filters have been designed and used by solar scientists to study the Sun. Prior to assembling these types of filters, each component, e.g., polarizers and wave plates, is characterized to determine its polarimetric parameters to ensure the desired filter design performance. With time and cost becoming an ever increasing issue, it is imperative to test components designated for a birefringent filter efficiently. This article addresses a shift to increased efficiency when testing components of very low volume (< 5 units) solar research filters that minimizes high priced hardware expenditures, i.e., Mueller matrix spectro-polarimeter.

Keywords (OCIS):

  • (280.0280) Remote sensing and sensors : Remote sensing and sensors
  • (300.0300) Spectroscopy : Spectroscopy
  • (230.7408) Optical devices : Wavelength filtering devices

The errors crosstalk analysis and compensation in the simultaneously measuring system for five-degree-of-freedom geometric error

  • Shuai GAO, Bin Zhang, Qibo Feng, Cunxing CUI, Shiqian CHEN, and Yuqiong Zhao
  • received 10/13/2014; accepted 12/09/2014; posted 12/09/2014; Doc. ID 224934
  • [full text: PDF (2080) KB)]
  • Abstract: This paper presents the analysis and compensation of the errors crosstalk in our developed simultaneously measuring system for five-degree-of-freedom geometric error. The errors crosstalk, including the yaw crosstalk to the horizontal straightness, the pitch crosstalk to the vertical straightness, the roll crosstalk to the horizontal and vertical straightness, and the roll real value crosstalk to the roll measured value can all be eliminated with the compensation. A series of experiments is conducted, and the results verify the compensation effect. For a linear stage, compared with an electronic level and a laser interferometer, the residuals are less than 2" when the roll errors are compensated, and the largest residuals for the compensated horizontal and vertical straightness are 1.9 μm and 3.5 μm respectively.

Keywords (OCIS):

  • (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
  • (120.1680) Instrumentation, measurement, and metrology : Collimation
  • (120.4640) Instrumentation, measurement, and metrology : Optical instruments

Background elimination and interferometric capability in optical coherence tomography by nonlinear optical gating based on type II second harmonic generation

  • Kamel Mallat, Amin Amin, Alain Cornet, Xavier Urbain, José Fernández, abdessitir deraoui, and Cristina Trillo
  • received 09/02/2014; accepted 12/09/2014; posted 12/10/2014; Doc. ID 222415
  • [full text: PDF (1134) KB)]
  • Abstract: A novel method that uses nonlinear optical gating to control the background illumination in optical coherence tomography is presented. With this method the user can adjust the amount of the undesired backscattering or eliminate it completely, which enables dark field measurements. The interferometric capability of the method in a nonlinear optical regime is demonstrated with the coupling of three overlapping input waves to yield Fizeau fringes. The measurement of a 265 nm step was performed to validate this method, which was originally conceived for three dimensional MEMS characterization.

Keywords (OCIS):

  • (110.0110) Imaging systems : Imaging systems
  • (190.0190) Nonlinear optics : Nonlinear optics
  • (320.0320) Ultrafast optics : Ultrafast optics

Comparison of Different Models for Ground-Level Atmospheric Turbulence Strength (Cn2) Prediction with New Models According to Local Weather Data for FSO Applications

  • Arockia Raj and Arputha Vijaya J
  • received 09/05/2014; accepted 12/09/2014; posted 12/10/2014; Doc. ID 222527
  • [full text: PDF (874) KB)]
  • Abstract: Atmospheric parameters strongly affect the performance of Free Space Optical Communication system when the optical wave is propagating through the inhomogeneous turbulence transmission medium. Developing models to get an accurate prediction of turbulence strength according to meteorological parameters becomes significant to understand the behavior of channel in different seasons. A dedicated Free Space Optical link for the range of 0.5km at an altitude of 15.25m is established and explained. The power level and beam centroid information of the received signal with meteorological parameters at the same time are continuously measured using the opto-electronic assembly and developed weather station respectively and stored in a data logging computer. The existing models selected, based on exhibiting relatively less prediction error, for comparative analysis are briefed. Measured meteorological parameters (as input factors) and turbulence strength (as response factor) of size [20004] are used for linear regression analysis and to design the mathematical models more suitable at the test field. Along with the model formulation methodologies, contribution of input factors’ individual & combined effects on the response surface and coefficient of determination (R2) estimated using ANalysis Of VAriable tools are presented. Model equation-V (R2=98.93%) is finalized for predicting turbulence strength. In addition, the prediction accuracy of the proposed and selected models for different seasons in one year period are investigated and validated in terms of Sum of Absolute Error (SAE). The average SAE of 0.000641x10-9m-2/3 for turbulence strength is achieved using the new model in longer range dynamic of meteorological parameters in different local seasons.

Keywords (OCIS):

  • (010.1300) Atmospheric and oceanic optics : Atmospheric propagation
  • (010.1330) Atmospheric and oceanic optics : Atmospheric turbulence
  • (010.3310) Atmospheric and oceanic optics : Laser beam transmission
  • (120.3940) Instrumentation, measurement, and metrology : Metrology
  • (130.0250) Integrated optics : Optoelectronics
  • (060.2605) Fiber optics and optical communications : Free-space optical communication

Horizontal Slot Waveguides for Polarization Branching Control

  • Ding-Wei Huang, Nai-Chia Cheng, Yao-Feng Ma, PoHan Fu, and Chun-Chieh Chin
  • received 10/13/2014; accepted 12/09/2014; posted 12/10/2014; Doc. ID 224081
  • [full text: PDF (1576) KB)]
  • Abstract: The capability of polarization branching control of silicon-on-insulator (SOI) horizontal-slot-waveguides-based directional couplers (DC) was investigated, and a highly efficient polarization beam splitters (PBS) and a polarization-independent directional couplers (PIDC) were proposed by tailoring the ratio of the coupling lengths for quasi-TE and quasi-TM modes. Due to the structural birefringence, the coupling effects of the quasi-TE and quasi-TM modes in the directional couplers may vary with the waveguide geometry, and numerical simulations were conducted to obtain the optimal design parameters for high efficiency and compact device size by varying the aspect ratios and waveguide spacing. The coupling lengths of the designed PBS and PIDC are 65.87 µm and 6.93 µm, respectively. They deliver good performance with extinction ratios of approximately 20 dB for PBS and 15 dB for PIDC. These devices are also broadband with a 1-dB bandwidth larger than 30 nm /100 nm. The fabrication error tolerance of the practical device is also discussed.

Keywords (OCIS):

  • (060.1810) Fiber optics and optical communications : Buffers, couplers, routers, switches, and multiplexers
  • (130.3120) Integrated optics : Integrated optics devices
  • (130.5440) Integrated optics : Polarization-selective devices

Thermally optimized variable optical attenuators on polymer platform

  • Ziyang Zhang, Alejandro Novo, Gelani Irmscher, Andrzej Polatynski, Tim Mueller, David Felipe, Moritz Kleinert, Walter Brinker, Crispin Zawadzki, and Norbert Keil
  • received 10/06/2014; accepted 12/09/2014; posted 12/10/2014; Doc. ID 224345
  • [full text: PDF (2070) KB)]
  • Abstract: Variable optical attenuators based on 1×1 MMI and Mach-Zehnder interferometer have been designed, fabricated and characterized. Thermo-optic simulations have been performed to find the optimal heater electrode layout in order to improve the heating efficiency, suppress thermal crosstalk, and enhance the dynamic attenuation range. Both types of attenuators feature low optical loss (< 0.7 dB). The compact 1×1 MMI provides a dynamic attenuation range of 35 dB over C-band at 10.1 mW heater power, while the Mach-Zehnder interferometer boosts the dynamic range beyond 50 dB at merely 1.8 mW heater power.

Keywords (OCIS):

  • (130.3120) Integrated optics : Integrated optics devices
  • (160.6840) Materials : Thermo-optical materials
  • (130.5460) Integrated optics : Polymer waveguides

Fabrication third-order polymer chirped waveguide Bragg grating with tapered core size by contact lithography

  • Bin Yun, Guohua Hu, Ruohu Zhang, and Yiping Cui
  • received 10/16/2014; accepted 12/09/2014; posted 12/10/2014; Doc. ID 225071
  • [full text: PDF (1284) KB)]
  • Abstract: A polymer chirp waveguide Bragg grating by using uniform grating structures on tapered waveguide core is designed and demonstrated. Third-order uniform grating structures were formed in the bottom cladding by cheap contact lithography and then channel waveguide with tapered core size was fabricated on top of it to realized the chirp waveguide Bragg grating. The reflection spectrum of the fabricated polymer chirp waveguide Bragg grating was measured and the 3dB bandwidth is 2.9nm, which is about 6.5 times as the 3dB bandwidth (0.45nm) of the fabricated uniform waveguide Bragg grating. Besides, the measured reflectivity is larger than 16dB and the reflection spectrum of the fabricated chirp waveguide Bragg grating was numerically simulated, which is in accordance with the experiment result very well.

Keywords (OCIS):

  • (230.1480) Optical devices : Bragg reflectors
  • (230.3120) Optical devices : Integrated optics devices
  • (130.7408) Integrated optics : Wavelength filtering devices
  • (130.5460) Integrated optics : Polymer waveguides

Influences of color centers absorption on the spectrum properties of the temperature dependent radiation induced attenuation

  • Yunxia Hou, Jing Jin, and chunjing liu
  • received 06/11/2014; accepted 12/09/2014; posted 12/09/2014; Doc. ID 213765
  • [full text: PDF (1175) KB)]
  • Abstract: Spectra ranged from 800nm to 1650nm of the temperature dependent Radiation Induced Attenuation (RIA) in the irradiated and sufficiently annealed fiber has been measured. Properties of these attenuation spectra were investigated based on the mechanism of color centers absorption. Using configurational coordinate model, these spectra were decomposed by absorption bands of three kinds of color centers. An elaborate analysis has been made on the influences of color centers absorption on the spectrum properties of temperature dependent RIA. At last, the RIA at three commonly used telecom wavelengths has been measured. The measuring results verify the correctness of the analysis of the spectrum properties.

Keywords (OCIS):

  • (060.2300) Fiber optics and optical communications : Fiber measurements
  • (060.2400) Fiber optics and optical communications : Fiber properties
  • (120.6780) Instrumentation, measurement, and metrology : Temperature
  • (350.5610) Other areas of optics : Radiation

A practical rotation angle measurement method by monocular vision

  • Dong Xin, Fu Qiang, Zhao Xu, Quan Quan, and Zhang Feng
  • received 10/01/2014; accepted 12/08/2014; posted 12/09/2014; Doc. ID 223990
  • [full text: PDF (1417) KB)]
  • Abstract: A practical vision-based method is proposed to measure single axis rotation angles. Compared with existing angle measurement methods, the proposed method in this paper is more practical because of simple equipments required and an easy installation. Furthermore, unlike most existing methods, the proposed method does not require the rotation axis information at all. It is calibrated by two view geometry of single axis motion. Then, on the basis of the calibration results, a point matching and angle estimation algorithm is proposed. Experiments on synthetic and real images show that our method is robust with respect to image noises and occlusion. The measurement accuracy is less than 0.15° only using a provided camera and a printed checkboard. Moreover, we develop a single axis rotation angle measurement toolbox using a camera and a checkboard, which is available online.

Keywords (OCIS):

  • (350.4600) Other areas of optics : Optical engineering
  • (150.1135) Machine vision : Algorithms
  • (150.1488) Machine vision : Calibration
  • (330.7325) Vision, color, and visual optics : Visual optics, metrology

Realization of self-guided unidirectional waveguides by a chain of gyro-magnetic rods

  • Rui-xin Wu, qingbo li, zhen li, and Yin Poo
  • received 07/16/2014; accepted 12/07/2014; posted 11/04/2014; Doc. ID 217074
  • [full text: PDF (1955) KB)]
  • Abstract: To achieve miniature dimension and flexibility, we propose unidirectional waveguide composed by a chain of gyro-magnetic rods. Two configurations of the waveguides were explained, one is of zigzag chain, another has straight-line chain. We find for these two configurations the waveguides have very wide edge mode bandwidths, in which there may have one-way transmissions (OWT). Both simulated and measured results illustrate that these two types of chain MPC waveguides could exhibit wideband OWT characteristics. And they are very flexible for practical application because of their thin transverse dimensions.

Keywords (OCIS):

  • (240.6690) Optics at surfaces : Surface waves
  • (350.4010) Other areas of optics : Microwaves
  • (050.5298) Diffraction and gratings : Photonic crystals

Hyperspectral absorption coefficient of "pure" seawater in the 350-550 nm range

  • Zhongping Lee, Jianwei Wei, Kenneth Voss, Marlon Lewis, Annick Bricaud, and Yannick Huot
  • received 10/20/2014; accepted 12/06/2014; posted 12/09/2014; Doc. ID 225317
  • [full text: PDF (667) KB)]
  • Abstract: Hyperspectral (every 5 nm) absorption coefficients of "pure" seawater in the 350-550 nm range are derived from remote-sensing reflectance measured in oligotrophic oceans. The absorption spectrum in this range is generally lower (and much lower in the 350-410 nm range) than the commonly adopted standard for ocean color processing and shows different spectral curvatures. Application of this new spectrum resulted in better retrievals of phytoplankton absorption coefficient in oligotrophic oceans, and will provide better closure of remote sensing reflectance for the UV-visible domain.

Keywords (OCIS):

  • (010.4450) Atmospheric and oceanic optics : Oceanic optics
  • (010.7340) Atmospheric and oceanic optics : Water
  • (010.1030) Atmospheric and oceanic optics : Absorption
  • (010.0280) Atmospheric and oceanic optics : Remote sensing and sensors

Retrieval of phytoplankton and CDM absorption coefficients with remote sensing reflectance in an ultraviolet (UV) band

  • Jianwei Wei and Zhongping Lee
  • received 10/23/2014; accepted 12/06/2014; posted 12/09/2014; Doc. ID 225562
  • [full text: PDF (1647) KB)]
  • Abstract: The light absorption of phytoplankton and colored detrital matter (CDM which includes contribution of gelbstoff and detrital matters) has distinctive yet overlapping features in the ultraviolet (UV) and visible domain. The CDM absorption (adg) increases exponentially with decreasing wavelength while the absorption coefficient of phytoplankton (aph) generally decreases towards the shorter bands for the range of 350-450 nm. It has long been envisioned that including ocean color measurements in the ultraviolet range may help the separation of these two components from the remotely sensed ocean color spectrum. An attempt is made in this study to provide an analytical assessment of this expectation. We started with the development of a new absorption decomposition model (QAA-UV), analogous to the quasi-analytical algorithm (QAA), that partitions the total absorption coefficient using information at bands 380 nm and 440 nm. Compared to the retrieval results relying on the absorption information at 410 nm and 440 nm of the original QAA, our analyses indicate that QAA-UV can improve the retrieval of aph and adg, although the improvement in accuracy is not significant for values at 440 nm. The performance of the UV-based algorithm is further evaluated with in situ measurements. The limited improvement observed with the field measurements highlights that the separation of the adg and aph is influenced by the accuracy of the ocean color measurements and the estimated total absorption coefficient, as well as the importance of having high-quality measurements.

Keywords (OCIS):

  • (010.0010) Atmospheric and oceanic optics : Atmospheric and oceanic optics
  • (010.4450) Atmospheric and oceanic optics : Oceanic optics
  • (010.4455) Atmospheric and oceanic optics : Oceanic propagation
  • (280.4991) Remote sensing and sensors : Passive remote sensing
  • (010.1030) Atmospheric and oceanic optics : Absorption
  • (010.0280) Atmospheric and oceanic optics : Remote sensing and sensors

Use of Customizing Kernel Sparse Representation for Hyperspectral Image Classification

  • Bin Qi, Zhao Chunhui, and Guisheng Yin
  • received 09/02/2014; accepted 12/05/2014; posted 12/10/2014; Doc. ID 222150
  • [full text: PDF (704) KB)]
  • Abstract: Sparse representation based classification (SRC) has attracted increasing attention in remote-sensed hyperspectral communities for its competitive performance with available classification algorithms. Kernel sparse representation based classification (KSRC) is a nonlinear extension of SRC, which makes pixels from different classes linearly separable. However, KSRC only considers projecting data from original space into feature space with a predefined parameter, without integrating priori domain knowledge, such as the contribution from different spectral feature. In this study, customizing kernel sparse representation based classification (CKSRC) is proposed by incorporating kth nearest neighbor density as a weighting scheme in traditional kernels. Analyses were conducted on a public data set with 9 selected land-cover classes. In comparison with traditional SRC and KSRC, the proposed CKSRC further increases the overall classification accuracy and presents robust classification results with different selection of training samples.

Keywords (OCIS):

  • (100.0100) Image processing : Image processing
  • (100.2960) Image processing : Image analysis
  • (010.0280) Atmospheric and oceanic optics : Remote sensing and sensors

(DH3D2014) Adaptive non separable vector lifting scheme for digital holographic data compression

  • Yafei Xing, Mounir Kaaniche, Beatrice Pesquet-Popescu, and Frederic Dufaux
  • received 09/02/2014; accepted 12/05/2014; posted 12/08/2014; Doc. ID 222055
  • [full text: PDF (1253) KB)]
  • Abstract: Holographic data plays a crucial role in the recent three dimensional imaging as well as microscopic applications. As a result, huge amounts of storage capacity will be involved for this kind of data. Therefore, it becomes necessary to develop efficient hologram compression schemes for storage and transmission purposes. In this paper, we focus on the shifted distance information, obtained by the phase shifting algorithm, where two sets of difference data need to be encoded. More precisely, a non separable vector lifting scheme is investigated in order to exploit the two-dimensional characteristics of the holographic contents. Simulations performed on different 3D objects have shown the effectiveness of the proposed method in terms of bitrate saving and quality of reconstruction.

Keywords (OCIS):

  • (090.1760) Holography : Computer holography
  • (100.2000) Image processing : Digital image processing
  • (090.1995) Holography : Digital holography

Determination of the tangential surface profile of Toroidal beam line mirrors with polarization phase shifting Twyman-Green interferometer

  • Sanjib Chatterjee and Pavan Y
  • received 09/23/2014; accepted 12/05/2014; posted 12/09/2014; Doc. ID 223740
  • [full text: PDF (1414) KB)]
  • Abstract: A new technique for the measurement of tangential surface profile of Toroidal mirrors (TMs) used in Synchrotron radiation beam lines is proposed. A cylindrical lens (CL) placed in the collimated input (He-Ne laser) beam of a polarization Twyman-Green interferometer (TGI) forms line foci in the reference and test arms of the TGI. The effect of the sagittal curvature of the TM is eliminated by adjusting a line focus on the surface of the TM, along the central tangential section. Thus a toric test wavefront (TTW), with sagittal curvature identical to that of the incident cylindrical wavefront and tangential curvature with slope twice as that of the TM, is produced along the reflection direction. The TTW interferes with a reference cylindrical wavefront, generated by retro-reflecting the incident cylindrical wavefront from a reference plane mirror in the reference arm of the TGI, having identical curvature in the sagittal direction. Polarization phase shifting interferometry has been applied to obtain the tangential surface profile of the test TM. Results are compared with other methods. Advantages of the technique are that, only a plane reference mirror is needed to generate the reference beam and the technique is suitable for TMs with long tangential radii of curvature in kilometre regime.

Keywords (OCIS):

  • (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
  • (120.5050) Instrumentation, measurement, and metrology : Phase measurement
  • (120.6650) Instrumentation, measurement, and metrology : Surface measurements, figure
  • (340.7470) X-ray optics : X-ray mirrors

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