Sous la tutelle de :

Photonic chips for sensing

We develop and characterize optical integrated circuits based on waveguide photopatterning using classical photolithography or a laser writing system onto polymer or glass materials.

Chips are characterized using a fiber alignment bench to butt-couple incoming (visible to Mid-IR) laser light into the waveguides and measure the output signal with photodetectors, camera and/or spectrum analyzer.

Laser writing setup

Fabrication, characterization, simulation

Previous work permitted to realize hybrid polymer based circuits: MZI thermo-optic switches, MMI couplers, DWDM Phasar multiplexers, MMI humidity[i] and dihydrogen sensors[ii].

SEM images of a star coupler

Waveguiding optical near-field probes were also fabricated using hybrid[iii] polymers.

Actually, the efforts are concentrated on ternary chalcogenide glasses for applications in the infrared spectrum in collaboration with the ChV team of the ICGM physico-chemistry institute.

The ternary glass composition was determined to lower refractive index fluctuations impact, enhance lifetime thanks to thermal stability and extend transparency domain from middle infrared (4 to 20µm) to include near-infrared regions (1µm to 16µm).

 

Ternary glass composition

Low loss (1.3dB/cm) single mode waveguides at 4.2µm wavelength were developed for carbon dioxyde detection[iv].

   
   

Transverse structure design, fabricated waveguides, real modes analysis

Projects, in additional collaboration with COMIC team of ITAP lab part of the IRSTEA, deal with measurements in agriculture for environmental care.

A DigitAg funded project uses water absorption at 1.55µm wavelength for spray deposit drop detection and measurement with the goal to provide a tool for helping to reduce chemical intrans in agriculture[v].

A MUSE funded project aims for bio-functionalization of the glass surface so as to develop biosensors for plants diseases prevention in collaboration with the Biophotonic team of the L2C lab.


[i] R.K.Kribich, B.MacCraith, R.Copperwhite, B.Kolodziejczyk and H.Barry, Novel Chemical/Bio–Sensor platform based on multimode interference couplers, Sensors and Actuators B, vol. 107(1), pp.188–192, May 2005.

[ii] T. Mazingue, M. Lomello-Tafin, C. Hernandez-Rodriguez, M. Passard, L. Goujon, J.-L. Rousset, F. Morfin, F. Bosselet, G. Maulion, R. Kribich, P. Coudray, B. Rolland, T. Wood, J.Le Rouzo, F. Flory, J.-F. Laithier, Pellet photonic innovant gas sensor using catalysis and integrated photonics, Sensors and Actuators B 222, 133–140, January 2016.

[iii] A.Tsigara, B.Mourched, P.Falgayrettes, B.Belier, E.L.Nativel, R.Kribich, P.Etienne, S.Calas, P.Gall–Borrut, Fabrication and mechanical properties of an organo–mineral cantilever–based probe for near–field optical microscopy, Sensors and Actuators A 212 (2014) 12–17, 2014.

[iv] C.Vigreux, M.Vu Thi, G.Maulion, R.Kribich, M.Barillot, V.Kirschner, A.Pradel, Wide-range transmitting chalcogenide films and development of micro-components for infrared integrated optics applications, Optical Materials Express, Vol. 4, Issue 8, pp. 1617–1631, 2014.

[v] C. Vigreux, M. Bathily, R. Escalier, R.K. Kribich, A. Pradel, R. Bendoula, First steps towards the realization of optical sensors to characterize spray deposits of pesticides on the leaves of vine plants, 19th International Conference on Transparent Optical Networks (ICTON), 2017.

 

 

Active Optical Fibers for high-energy ionizing radiations

 

Since the early 2000s, the group has explored a new research theme regarding the transfer of the know-how acquired in the frame of the optical telecommunication technologies to embedded satellite applications. More precisely, we studied the behavior under radiations of erbium-doped amplifying optical fibers. This work was carried out through 3 PhD thesis, supported by a substantial ANR funding  and the fruit of long time and very rich scientific and industrial collaborations.

Thanks to a relatively complex experimental set up, and using gamma irradiation facilities, we monitored the optical gain decrease for different fiber samples, as a function of the deposited dose. The most promising candidates for broadband space applications meet the space specifications, that is to say a gain penalty below 1dB under a deposited dose of 300Gy, typically the dose received by a geostationary satellite during a full 10-15 years space mission.


Optical power decrease for each erbium-doped fiber-amplifier


By comparing the radiation resistance of optical amplifiers based on erbium-doped specialty fibers with various chemical compositions, we thus provided some technological solutions to design a radiation-hardened active fiber, or at least to design a fiber with a very low sensitivity to radiations, associated with a relevant bandwidth, without building specific coating, specific packaging, or any other cumbersome solutions.
Our work can provide valuable assistance to fiber technologists in designing optical amplifiers for specific applications in a radiative environment, taking into account the tricky tradeoff between the absolute gain level, the permissible gain penalty, the related bandwidth, and its flatness, in implementing simple well-known absorption and cutback measurements.

This tradeoff is illustrated through the following figure, that gives the evolution of the spectral gain versus the sample length, and the wavelength, for a given active fiber. The inset shows the dependence of the gain @ 1550nm on the sample length, obtained by the classical cutback method.

Optical amplifier gain spectra for different sample lengths


For further information, see our latest article relevant to this work :
R. Dardaillon et al., Broadband Radiation-Resistant Erbium-Doped Optical Fibers for Space Applications, IEEE Transactions on Nuclear Science, 64, 6, 1540-1548, 2017.

 

We are also working on the modeling component of these active fibers: we have developed a set of equations that models the degradation of Er-Al doped Silica fibers under radiations. The model takes into account the degradation kinetics of the Silica matrix under radiations as a function of the dose deposit, enhanced by the Erbium chemical conformation modification and including the main trap levels relevant to other elements (SiO2 , Ge and Al). Some parameters are provided by the literature and others come from various spectroscopic analyses.

The knowledge of the different defects allows to express the trap population kinetics through the energy diagram given below.

Si02 network configuration:
changes induced by irradiations in the glass (left)
and energy diagram for typical exchange (right)

Energy level scheme of the model describing the degradation of a Silica glass
doped with Germanium, Aluminum and/or Erbium

 

In spite of widely changing doping and co-doping elements concentration, we observe a relevant agreement between the whole experimental measurements and the numerical simulations of the Radiation-Induced-Absorption. The meeting between experimental and modelling results is illustrated in the next figure.


Normalized RIA for the fibers under test at the highest available total dose (200 to 300Gy)
and a dose rate of 0.4 Gy/h at 980 nm (a) and 1550 nm (b).


Thus, our model allows to predict the fiber degradation versus a dose deposit up to typically 1 kGy, as a function of the fiber core composition. Thanks to its accuracy, this model enables the engineering of radiation hardened or radiation sensitive optical fibers. As a consequence, this model appears to be very promising to design specific radiation-hardened optical amplifiers.


Paper in press in November 2019: Accurate modeling of radiation-induced absorption in Er-Al doped Silica fibers exposed to high-energy ionizing radiations, R. Dardaillon et al., Optics Express.