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1.
Appl Opt ; 59(22): 6760-6764, 2020 Aug 01.
Article in English | MEDLINE | ID: mdl-32749382

ABSTRACT

We present a method to obtain the phase modulation characteristic curve of a spatial light modulator (SLM) under severe vibration conditions. The procedure is based on the well-known advanced iterative algorithm (AIA), which allows wavefront extraction from unknown phase-shifted interferograms. Generally, AIA is used to determine the wavefront and the determined phase shifts are of little interest. In contrast, in our method, the main goal of using AIA is to determine the unknown phase shifts induced by an SLM during the calibration procedure. Using a segmented approach to calibration, AIA enables successful calibration even in the presence of additional random phase shifts due to environmental changes. This method has the potential to calibrate SLMs integrated in complex optical instruments with little to no modifications to the optical setup, no matter the environmental conditions. We demonstrate our technique by calibrating an SLM under vacuum conditions (10-5mbar) in a common-path configuration compatible with usage of an SLM as a wavefront modulator at the pupil plane of an instrument. Our technique compensates for the vibrations produced by the vacuum pumps and reduces an order of magnitude the root-mean-squared error of the calibration curve evaluated with vibration errors. Our technique enhances the potential use of SLMs in complex optical systems, including aerospace optical instrumentation.

2.
Opt Express ; 26(9): 12038-12048, 2018 Apr 30.
Article in English | MEDLINE | ID: mdl-29716120

ABSTRACT

Liquid crystal variable retarders (LCVR) based polarimeters perform temporal polarization modulation by applying a sequence of driving voltages to introduce different optical retardances. However, even after a careful design and fabrication, manufacturing tolerances (i.e., slight optical axis misalignments, instrument residual polarization, optical activity in the LCVRs...) or the final system configuration (i.e., LCVRs in a convergent optical beam, thermal gradient across the clear aperture...) produce deviations from the ideal setup. As a consequence, all of these effects can reduce the polarimetric modulation efficiency of the device and, therefore, its signal-to-noise ratio. Hence, the voltage sequence applied according to the LCVR calibration curves may not be suitable to reach the optimal theoretical polarimetric efficiencies. In this work, a systematic fine tuning method for the LCVRs driving voltages is described an experimentally demonstrated.

3.
Opt Lett ; 38(19): 3784-7, 2013 Oct 01.
Article in English | MEDLINE | ID: mdl-24081052

ABSTRACT

This Letter shows the effect of the geometrical and material properties of lead lines and connections on the robustness and reliability of optical antennas working as distributed bolometers. We analyze the operational limits of the biasing voltage using a mutiphysics finite element method. We demonstrate that, after evaluating the effect of the electromagnetic irradiance falling on the device, biasing voltage is the main limiting factor to maintain operative titanium optical antennas. Results have been experimentally verified by finding the biasing values needed to destroy optical antennas working as distributed bolometers. Structural damage has been identified from scanning electron microscopy images.

4.
Opt Express ; 21(9): 10867-77, 2013 May 06.
Article in English | MEDLINE | ID: mdl-23669943

ABSTRACT

Optical antennas and resonant structures have been extensively investigated due to its potential for electromagnetic detection and energy harvesting applications. However their integration into large arrays and the role of connection lines between individual antennas has drawn little attention. This is necessary if we want to exploit its potential constructively and to enable economical large-scale fabrication. In this contribution we point out some features that an efficient antenna array should address. Experimental measurements on aluminum microbolometers are compared to electromagnetic simulations, it is shown that the finite size of a real array and the interconnection lines interact and affect the global performance.


Subject(s)
Computer-Aided Design , Infrared Rays , Optical Devices , Radiometry/instrumentation , Transducers , Equipment Design , Equipment Failure Analysis
5.
Opt Express ; 20(21): 23875-86, 2012 Oct 08.
Article in English | MEDLINE | ID: mdl-23188353

ABSTRACT

An experimental setup to measure the three-dimensional phase-intensity distribution of an infrared laser beam in the focal region has been presented. It is based on the knife-edge method to perform a tomographic reconstruction and on a transport of intensity equation-based numerical method to obtain the propagating wavefront. This experimental approach allows us to characterize a focalized laser beam when the use of image or interferometer arrangements is not possible. Thus, we have recovered intensity and phase of an aberrated beam dominated by astigmatism. The phase evolution is fully consistent with that of the beam intensity along the optical axis. Moreover, this method is based on an expansion on both the irradiance and the phase information in a series of Zernike polynomials. We have described guidelines to choose a proper set of these polynomials depending on the experimental conditions and showed that, by abiding these criteria, numerical errors can be reduced.


Subject(s)
Algorithms , Lasers , Photometry/instrumentation , Tomography/instrumentation , Equipment Design , Equipment Failure Analysis , Infrared Rays
6.
Opt Express ; 19(27): 26079-87, 2011 Dec 19.
Article in English | MEDLINE | ID: mdl-22274196

ABSTRACT

An enhanced optical system design for NDIR gas detection is presented. Multiple paths lengths within the same cavity are used to auto reference the system. The system has good thermo-mechanical stability: it requires no special thermal stabilization, shows no sensitivity to thermal emitter drift and has no moving parts involved. Long term stability, virtually no zero-drift and sub-ppm level gas detection were achieved using commercial thermopile sensors and a thermal emitter modulated at low frequency (~0.5 Hz). Experimental tests were performed using carbon monoxide (CO) and a 30.5 cm cavity length. The design can be extended to allow multiple gas detection within the same optical cavity.


Subject(s)
Gases/analysis , Optical Devices , Photometry/instrumentation , Refractometry/instrumentation , Equipment Design , Equipment Failure Analysis
7.
Opt Lett ; 30(23): 3129-31, 2005 Dec 01.
Article in English | MEDLINE | ID: mdl-16342698

ABSTRACT

We have measured the optical phase sensitivity of fiber based on poly(methyl methacrylate) under near-single-mode conditions at 632.8 nm wavelength. The elongation sensitivity is 131 +/- 3 x 10(5) rad m(-1) and the temperature sensitivity is -212 +/- 26 rad m(-1) K(-1). These values are somewhat larger than those for silica fiber and are consistent with the values expected on the basis of the bulk polymer properties.

8.
Appl Opt ; 44(32): 6890-7, 2005 Nov 10.
Article in English | MEDLINE | ID: mdl-16294963

ABSTRACT

We demonstrate the sensitivity of Bragg gratings in a multicore fiber to transverse load. The Bragg peaks are split because of stress-induced birefringence, the magnitude of which depends upon the load and grating position relative to the load axis. Experiments show that a set of gratings in a four-core fiber can measure a load axis angle to +/- 5 degrees and a load magnitude to +/- 15 N m(-1) up to 2500 N m(-1). We consider alternative designs of multicore fiber for optimal load sensing and compare experimental and modeled data.

9.
Opt Lett ; 29(19): 2225-7, 2004 Oct 01.
Article in English | MEDLINE | ID: mdl-15524362

ABSTRACT

We present experimental measurements of the peak splitting of the reflection spectra of fiber Bragg gratings as a result of birefringence induced by transverse loading of a multicore fiber. Measurements show that the splitting is a function of the applied load and the direction of the load relative to the azimuth of the fiber. A model for calculating the stress in the fiber that is due to an applied load is in good agreement with our experimental observations.

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