Photonic space : optical thin film

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L’Espace Photonique : A technological platform dedicated to optical thin films

Created in September 2014 and inaugurated in June 2015, the Espace Photonique is a technological platform dedicated to experimental Optics and Photonics.
It includes 250 m² of clean rooms (10,000 and 100,000 class) dedicated to the fabrication and the characterization of optical interference filters.
Thus, the Espace Photonique is a unique platform in France for the realization of components based on optical thin films.

1. Substrate preparation before coating :

The Espace Photonique is equipped with an automatic cleaning machine (SIEM TCA 90) that allows reproducible and excellent cleaning of samples before coating. This step is crucial for layers adhesion as well as the final quality (cosmetics) of the fabricated layers especially for space or high power lasers applications.

Main characteristics :
• 3 cleaning modules (acids or bases) with ultrasounds,
• 2 rinsing modules
• 2 modules with deionized water (cleaning and rinsing)
• 1 drying module (lift-out)
• 1 waiting module

2. Deposition technologies

The Espace Photonique is equipped with 5 physical vapor deposition machines. Three of them on based on electron beam deposition and the other two on sputtering (ion beam or magnetron sputtering).

The Espace Photonique includes Plasma Assisted Reactive Magnetrons Sputtering (PARMS) machine, Bühler/Leybold Optics HELIOS machine, acquired in December 2012. This is, at this date, the single similar machine installed in France. The HELIOS machine is well adapted to the fabrication of complex optical interference filters composed with a large number of layers. We have demonstrated optical elements composed with more than 300 layers ( 150/face) with total thickness that can exceed more than 25 µm per face. The available spectral region is between 350 and 2500 nm. This machine has been recently used for the fabrication of complex bandpass filters for space applications or mirrors for high power lasers applications. Main characteristics of the machine are :

• 12 sample holders with 100 mm diameter including one for optical monitoring,
• Substrate holder palette rotating at 240 rd.min-1,
• Load-lock system,
• 4 distinct processing zones,
o 1 plasma assistance source,
o 2 MF magnetron sputtering sources (dielectric materials deposition),
o 1 DC magnetron sputtering source (metallic materials deposition),
• Live in-situ optical monitoring of the depositions (transmission measurement),
• Available targets : Si, Nb, Hf, Ta, Ag, Cr,
• Available gases : Ar, O2, N2

The Espace Photonique includes a Plasma assisted ion beam deposition system (Advanced Plasma Source, APS), Bühler/Leybold Optics SYRUSpro 710 machine acquired in February 2015. This machine allows the fabrication of high performances optical interference filters, and especially microstructured filters. This machine is used today for the fabrication of pixelated filters (CNES), the deposition of metal dielectric structures for the control of the colorimetry (on organic and inorganic substrates) or the demonstration of metamaterials.
Main characteristics of the machine are :

• 20 sample holders with 100 mm diameter,
• A mask for achieving uniformity within 1%,
• 3 processing zones,
o 1 Advanced Plasma Source,
o 2 electron beam guns (deposition of dielectric materials and metals),
• Live in-situ optical monitoring of the depositions (transmission measurement),
• Available materials : SiO2, Nb2O5, Ag, Au, Cu… (non-exhaustive list)

In addition to these two recent machines, the Espace Photonique includes a dual ion beam sputtering machine (DIBS) from Teer-Coatings Company. This machine was acquired in early 2000 and allows depositing layers with ultra-stable and repeatable deposition rates. This machine is thus used for the development of new optical monitoring techniques. In early 2000, it was also used for the fabrication of linearly variable filters.

Finally, the Espace Photonique is equipped with two Balzers electron beam deposition machine : one BAK 600, classical evaporation, and one BAK 750, ion assisted deposition (IAD). These machine are used today for the development of infrared coatings, and in particular chalcogenide glass based layers for the development of innovative volume elements.

3. Characterization systems of multilayer optical elements

The Espace Photonique also includes a characterization rooms that combines all required systems for the certification of the fabricated components. They allow characterizing both the optical and geometrical performances of the fabricated optical interference filters.
First of all, there are 2 spectrometers. One Perkin Elmer Lambda 1050 spectrophotometer that allows measuring transmission (T module) and absolute reflection (URA and 8RT module) within a spectral range from 200 up to 3200 nm and an angular domain between 8 and 70°. A Fourier Transform Infrared spectrometer (FTIR), Thermo Fischer Nicolet 6700, allows measuring transmission and reflection in a spectral region from 2.5 up to 20 µm.

The Espace Photonique also includes two instruments for the measurement of non-conventional spectral performances of optical filters.
• A low-loss measurement system, Novawave LossPro, based on Cavity Ring Down Spectroscopy (CRDS) that also allows characterizing high reflectance mirrors.
• An internally developed system that allows performing mappings of the local spectral performances of an optical filter. These measurements are then used to extract the uniformity of the deposited layers based on the type of fabricated component.

Finally, the Espace Photonique an optical profilometer based on white light interferometry (ZYGO Newview 7300) for the characterization of the flatness and the roughness of the fabricated components. This system includes :
• 3 microscope objectives (1X, 10X, 100X),
• 2 zooms (0,5X and 1X),
• One four-axis motorized positioning system (± 75 mm XY, ± 4° tip/tilt),
• One stitching software.

Contact : Julien Lumeau}}