High-precision measurements of reflectance

Voarino, Philippe; Petitrenaud, Sébastien; Piombini, Hervé; Sabary, F.; Marteau, Daniel

doi:10.1117/12.692235

Cited by 9 publications

(3 citation statements)

References 1 publication

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“…The resulting nanocomposites demonstrate tunable elastic properties and a possible self-healing effect thanks to the incorporation of PDMS into the SiO2 network. To optimize these films, we have used various techniques to identify the optical characteristics [17][18][19][20], measure their stress level [21] and determine their elastic modulus [5][6]22]. In this paper, we used a homemade nano-indenter built from a microscope equipped with an x*y motorized stage.…”

Section: Introductionmentioning

confidence: 99%

Indentation hardness and scratch tests for thin layers manufactured by sol-gel process

et al. 2021

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Section: Introductionmentioning

confidence: 99%

Indentation hardness and scratch tests for thin layers manufactured by sol-gel process

et al. 2021

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“…The design has already been presented during other meetings [2][3][4], and this optical system was patented [5]. The experimental set-up is summarized below and schematically drawn in Fig.…”

Section: Solution To Measure Opaque Samples With a Good Accuracy Insmentioning

confidence: 99%

High-Precision Measurements of the Specular Reflectivity

Piombini

Vaorino

Sabary

et al. 2007

Optical Interference Coatings

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The spectrophotometer described is designed to measure specular reflectance with a high degree of accuracy. It can measure shape piece, antireflective or reflective coating and make cartographies in order to detect heterogeneities of coating. The laser MegaJoule and reflectors of amplifying sectionsThe MegaJoule Laser Project (LMJ) and the National Ignition Facility (NIF) constitute a great technological challenge of this century, more particularly for the optical components. A laser source is amplified to reach 1.8 million Joule in order to realize fusion reactions. This paper deals with new design developed to measure the reflectivity of the optical components, in particular the reflectors of LMJ amplifiers. These metallic reflectors have a selected shape to yield the best results and are coated with a cheap process. The technical specifications of these reflectors indicate their dimension and their shape: the elements are till 2 meters high and may be not plane (corners, valleys, wavelets …). To prevent them from oxidation and abrasion due to cleaning during the life of reflectors, the reflective layer is protected by a transparent SiO 2 layer [1]. Reflector industrialization is based on technical specifications which must be achieved and qualified, particularly for the spectral reflectance. Indeed, the reflection at the wavelength of 600 nm must be higher than 96 % by taking into account the uncertainty of measurement. This requires the best precision concerning measuring instrument. Solution to measure opaque samples with a good accuracy, instrument designThe design has already been presented during other meetings [2][3][4], and this optical system was patented [5]. The experimental set-up is summarized below and schematically drawn in Fig. 1. At first, it is designed to measure the specular reflectance of mirrors over the 420 to 950 nm wavelength range. The light beam is conditioned to enter in the monochromator which selects one wavelength. The signal is filtered spatially, spectrally and temporarily modulated. The beam is divided into two ways, one for reference and one for measurement. The sample holder is fixed on a three-axis translation stage. It enables to obtain mappings (y&z stages) and conjugates (x stage) automatically the photodiode with the surface of the sample, thanks to a video way. Once this conjugation is achieved, signals are acquired by lock-in amplifiers for several seconds in order to make an average and to reject values outside the range defined by three times the standard deviation. By calculating the ratio between the measurement and the reference ways, problems due to the fluctuations in the source output, the atmospheric absorption and the non-uniformity of the detector are reduced. This process is realized for each wavelength.

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“…To obtain the best optical performances, metrology tools such as spectrophotometers [1][2][3][4][5] were fielded at optic fabrication vendors to assure production control. Nowadays, commercial spectrophotometers used in optical measurement have a good precision of transmittance (0.2% to 0.5%) and reflectance (0.2% to 1%).…”

Section: Introductionmentioning

confidence: 99%

Precise measurement of transmittance and reflectance for large aperture optics

et al. 2014

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The uniformity measurement, transmittance and reflectance of the optics in other words, is one of the essential specifications for those large optics of high power laser facilities. Both high reproducibility for large-size and precision with wide dynamic range make such testing a real challenge to take.In this paper, a transmittance and reflectance measurement system with large aperture is demonstrated. With a laser source at 1053nm, three kinds of large aperture optics are tested by conventional direct detection. The results show that this system can realize high measuring precision (0.05% and 0.01% for transmittance and reflectance respectively) when tested parameter is small in value. In addition, the measurements precision with 532nm and 351nm laser sources are also tested compared, and the factors of measurement uncertainty with shorter wavelength are analyzed.To further promote accuracy and signal-noise ratio, coherent heterodyne detection and optical demodulation technique is proposed especially for high transmittance measurement. A demonstrative experiment of transmittance detection by balanced heterodyne and optical demodulation is performed, and a SD=0.052%, which is more than two order precision is achieved. It results that it is valid compared with conventional direct detection, and gives a promising method for higher precision during further practical applications.

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High-precision measurements of reflectance

Cited by 9 publications

References 1 publication

Indentation hardness and scratch tests for thin layers manufactured by sol-gel process

Indentation hardness and scratch tests for thin layers manufactured by sol-gel process

High-Precision Measurements of the Specular Reflectivity

Precise measurement of transmittance and reflectance for large aperture optics

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