Design and manufacturing of high-performance notch filters

Schallenberg, Uwe B.; Ploss, B.; Lappschies, Marc; Jakobs, Stefan

doi:10.1117/12.856580

Cited by 12 publications

(6 citation statements)

References 13 publications

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“…Experience with the MAGIC telescopes has shown, that additionally the laser beam can confuse the star-guider analysis software, used to correct the pointing of the telescopes with the help of CCD cameras. Whereas solutions based on Notch-filters (Schallenberg et al 2010) exist for the CCD cameras, similar approaches for the CTA camera pixels require future study and some innovation effort: coating of curved surfaces with filters is not straight-forward, nor thin filters resisting all types of weather phenomena, like temperature changes, humidity cycles, etc. to which, for instance, a protecting plexiglas of the cameras is exposed during night.…”

Section: Discussionmentioning

confidence: 99%

“…from Cherenkov light pulses) the star guider camera and the precision pointing of the telescopes, and ultimately, d) by affecting the duty cycle, if active laser avoidance is chosen. Several of the enumerated problems can be often overcome with the use of Notch-filters (Schallenberg et al 2010) or band-pass filters (Ahnen et al 2017;Archambault et al 2017), however this is not always possible at a reasonable cost, particularly not in the case of the CTA, where every camera pixel would need to be covered by such a filter. Light losses at smaller wavelengths, particularly in the sensitive region from 300 nm to 500 nm need to be strictly controlled in order to ensure that sensitivity losses remain acceptable, particularly around the energy threshold of the CTA.…”

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confidence: 99%

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Impact of Laser Guide Star facilities on neighbouring telescopes: the case of GTC, TMT, VLT, and ELT lasers and the Cherenkov Telescope Array

Gaug

Doro

2018

Monthly Notices of the Royal Astronomical Society

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Powerful Laser Guide Star (LGS) systems are standard for the next-generation of extremely large telescopes. However, modern earth-based astronomy has gone through a process of concentration on few sites with exceptional sky quality, resulting in those becoming more and more crowded. The future LGS systems encounter hence an environment of surrounding astronomical installations, some of which observing with large fields-of-view. We derive formulae to calculate the impact of LGS light on the camera of a neighbouring telescope and the probabilities for a laser crossing the camera field-of-view to occur, and apply these to the specific case of the next very-high-energy gamma-ray observatory "Cherenkov Telescope Array" (CTA). Its southern part shall be constructed in a valley of the Cerro Armazones, Chile, close to the "Very Large Telescope" (VLT) and the "European Extremely Large Telescope" (ELT), while its northern part will be located at the "Observatorio del Roque de los Muchachos", on the Canary Island of La Palma, which also hosts the "Gran Telescopio de Canarias" (GTC) and serves as an optional site for the "Thirty Meter Telescope" (TMT), both employing LGS systems. Although finding the artificial star in the field-of-view of a CTA telescope will not disturb observations considerably, the laser beam crossing the field-of-view of a CTA telescope may be critical. We find no conflict expected for the ELT lasers, however, 1% (3%) of extra-galactic and 1% (5%) of galactic observations with the CTA may be affected by the GTC (TMT) LGS lasers, unless an enhanced version of a laser tracking control system gets implemented.creation of several guide stars is also possible, to achieve asterism with a radial distance from science target ranging from 0.5 to 6 on the sky. The LGS will likely be operated regularly during observations, and their scattered light (Rayleigh and Mie) will then be seen by other telescopes until distances of several kilometers from the location of their host observatory. Assuming the close-by installation observes in a wavelength range enclosing that of the LGS lasers, the scattered laser light may then leave spurious light tracks on the cameras and affect operation in several ways: a) by generating false triggers (for installations which trigger image readout e.g. from Cherenkov light pulses) the star guider camera and the precision pointing of the telescopes, and ultimately, d) by affecting the duty cycle, if active laser avoidance is chosen. Several of the enumerated problems can be often overcome with the use of Notch-filters (Schallenberg et al. 2010) or band-pass filters (Ahnen et al. 2017;Archambault et al. 2017), however this is not always possible at a reasonable cost, particularly not in the case of the CTA, where every camera pixel would need to be covered by such a filter. Light losses at smaller wavelengths, particularly in the sensitive region from 300 nm to 500 nm need to be strictly controlled in order to ensure that sensitivity losses remain acceptable, particularly around the energ...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Impact of Laser Guide Star facilities on neighbouring telescopes: the case of GTC, TMT, VLT, and ELT lasers and the Cherenkov Telescope Array

Gaug

Doro

2018

Monthly Notices of the Royal Astronomical Society

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“…In other words, the notch filter can selectively reflect a portion of the spectrum while transmitting all other wavelengths. In the related literature, the use of high-end multilayer film manufacturing technology includes the advancedplasma-source (APS) assisted electron beam evaporation [1], plasma assisted reactive magnetron sputtering (PARMS) [2][3][4], HELIOS (Leybold Optics) magnetron sputtering [5,6], ion-assisted electron beam evaporation [7], etc. Among them, electron beam evaporation technology has the potential for industrialized mass production and application.…”

Section: Introductionmentioning

confidence: 99%

Design and Fabrication of a Cost-Effective Optical Notch Filter for Improving Visual Quality

et al. 2021

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This study presents a multilayer design and fabrication of an optical notch filter for enhancing visual quality. A cost-effective multilayer design of notch filter with low surface roughness and low residual stress is proposed. A 9-layer notch filter composed of SiO2 and Nb2O5 with a central wavelength of 480 nm is prepared by electron beam evaporation combined with ion-assisted deposition. The optical transmittance, residual stress, and surface morphology are measured by a UV/VIS/NIR spectrophotometer, Twyman-Green interferometer and field emission scanning electron microscopy (FE-SEM). The transmittance of the notch filter at the central wavelength is above 15%, and the average transmittance of the transmission band is about 80%. The residual stress of the notch filter is −0.235 GPa, and the root mean square surface roughness is 1.85 nm. For improving the visual quality, a good image contrast can be obtained by observing the microscopic image using the proposed notch filter.

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“…Along with general purpose design techniques such as refinement, needle optimization, gradual evolution [1][2][3][4][5], special approaches aimed at different types of multilayer coatings are being actively developed. For example, specific methods for designing dispersive mirrors [6,7], minus and notch filters [8][9][10][11], WDM filters [12,13] have been implemented by different authors.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity-directed refinement for designing broadband blocking filters

Amotchkina

Brauneck²,

Tikhonravov

et al. 2015

Opt. Express

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We developed a new method aimed at designing short-pass filters, long-pass filters and filters blocking sidebands of Fabry-Perot bandpasses. The method is an automated version of a non-straightforward empirical approach invented as a result of many years' experience in design and production of optical coatings. The method allows obtaining near-quarter-wave solutions in a few seconds. In many cases these solutions are more advantageous for deposition systems.

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Design and manufacturing of high-performance notch filters

Cited by 12 publications

References 13 publications

Impact of Laser Guide Star facilities on neighbouring telescopes: the case of GTC, TMT, VLT, and ELT lasers and the Cherenkov Telescope Array

Impact of Laser Guide Star facilities on neighbouring telescopes: the case of GTC, TMT, VLT, and ELT lasers and the Cherenkov Telescope Array

Design and Fabrication of a Cost-Effective Optical Notch Filter for Improving Visual Quality

Sensitivity-directed refinement for designing broadband blocking filters

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