Drift in Interference Filters Part 1

Title, A. M.; Pope, T.; Andelin, John P.

doi:10.1364/ao.13.002675

Cited by 18 publications

(3 citation statements)

References 1 publication

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“…15,21 Coatings that are subjected to very low temperatures, usually shift toward shorter wavelengths, consistent with their behavior at elevated temperatures.…”

Section: Multilayersmentioning

confidence: 77%

<title>Performance-Limiting Factors In Optical Coatings</title>

Macleod

1981

SPIE Proceedings

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“…15,21 Coatings that are subjected to very low temperatures, usually shift toward shorter wavelengths, consistent with their behavior at elevated temperatures.…”

Section: Multilayersmentioning

confidence: 77%

<title>Performance-Limiting Factors In Optical Coatings</title>

Macleod

1981

SPIE Proceedings

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“…Because both the indices and thicknesses of the individual layer materials depend on temperature, the transmission or reflection spectrum is also a function of temperature. 15,16 Thus, when a wavelength l 1 of incident light on the filter is located near the edge of the transmission or reflection spectrum passband of the filter, the intensity of the transmission or reflection will be a function of temperature, which is the basis of the operation of the sensors described in this paper. However, as addressed in Section 1, a major problem associated with intensity-based fiber sensors is the signal drifts caused by optical-power variations.…”

Section: Temperature Sensorsmentioning

confidence: 99%

Fiber-optic temperature sensors based on differential spectral transmittance/reflectivity and multiplexed sensing systems

Wang

Murphy

et al. 1995

Appl. Opt.

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A concept for optical temperature sensing based on the differential spectral reflectivity@transmittance from a multilayer dielectric edge filter is described and demonstrated. Two wavelengths, l 1 and l 2 , from the spectrum of a broadband light source are selected so that they are located on the sloped and flat regions of the reflection or transmission spectrum of the filter, respectively. As temperature variations shift the reflection or transmission spectrum of the filter, they change the output power of the light at l 1 , but the output power of the light at l 2 is insensitive to the shift and therefore to the temperature variation. The temperature information can be extracted from the ratio of the light powers at l 1 to the light at l 2 . This ratio is immune to changes in the output power of the light source, fiber losses induced by microbending, and hence modal-power distribution fluctuations. The best resolution of 0.2°C has been obtained over a range of 30-120°C. Based on such a basic temperature-sensing concept, a wavelength-division-multiplexed, temperature-sensing system is constructed by cascading three sensingedge filters that have different cutoff wavelengths along a multimode fiber. The signals from the three sensors are resolved by detecting the correspondent outputs at different wavelengths.

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“…Thermal annealing is a process commonly used to enhance the performance of amorphous optical coatings [1][2][3]. It can increase the transmittance [4] and stability [5], and reduce the absorptance [6] and the stress which might result from optical coatings deposition [7,8]. For these reasons, thermal annealing is mandatory for high-performance amorphous coatings, such as the ones used as mirrors in gravitational wave detectors (GWD) [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Monitoring the evolution of optical coatings during thermal annealing with real-time, in situ spectroscopic ellipsometry

Colace,

Samandari,

Granata

et al. 2024

Class. Quantum Grav.

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Thermal annealing plays a key role in optimizing the properties of amorphous optical coatings. In the field of gravitational wave detection (GWD), however, the effects of annealing protocols on the interferometry mirror coatings have been explored primarily by ex post analysis. As a result, the dynamics of the coatings properties during annealing is still poorly known, potentially leading to suboptimal performance. Here, using real-time, in situ spectroscopic ellipsometry (SE) we have tracked the refractive index and thickness of a titania-tantala coating during controlled annealing. We have tested the material and the annealing protocol used incurrent GWD mirrors. The annealing cycle consisted of a heating ramp from room temperature to 500 °C, followed by a 10-hour plateau at the same temperature and the final cooling ramp. SE measurements have been run continuously during the entire cycle. Significant variations in the thickness and refractive index, which accompany the coating structural relaxation, have been recorded during the heating ramp. These variations start around 200 °C, slightly above the deposition temperature, and show an increased rate in the range 250-350 °C. A smaller, continuous evolution has been observed during the 10-hour high-temperature plateau. The results offersuggestions to modify the current annealing protocol for titania-tantala coatings, for example by increasing the time duration of the high-temperature plateau. They also suggest an increase in the substrate temperature at deposition. The approach presented here paves the way for systematic, real-time investigations to clarify how the annealing parameters shape the properties of optical coatings, and can be leveraged to define and optimize the annealing protocol of new candidate materials for GWD mirrors.

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Drift in Interference Filters Part 1

Cited by 18 publications

References 1 publication

<title>Performance-Limiting Factors In Optical Coatings</title>

<title>Performance-Limiting Factors In Optical Coatings</title>

Fiber-optic temperature sensors based on differential spectral transmittance/reflectivity and multiplexed sensing systems

Monitoring the evolution of optical coatings during thermal annealing with real-time, in situ spectroscopic ellipsometry

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