The mid-infrared molecular fingerprint region has gained great interest in the last decade thanks to development of on-chip semiconductor lasers and mid-IR optical fibers. For integrated-optic devices and optical sensors based on interferometric techniques, versatile and easy handling devices can be required. In this context, low-loss single-mode chalcogenide microstructured optical fibers (MOF) which presents an antireflection coating have been elaborated in order to be connected to a Distributed Feedback Quantum Quantum Cascade Laser (DFB-QCL). In addition, another original design of a chalcogenide MOF has been also realized in order to obtained high birefringence properties that can permit to maintain the polarization of the QCL at the output of the fiber. Finally, the fiber properties have been evaluated using a DFB-QCL emitting at 7.4 µm and the polarization maintaining of the chalcogenide fiber has been demonstrated.
The combination between a DFB-QCL with such non-conventional fibers has led to the development of single-mode fibered Mid IR lasers.
 J. Troles, L. Brilland, C. Caillaud, J.-L. Adam, Advanced Device Materials, 3 (2017) 7-13.
 C. Caillaud, C. Gilles, L. Provino, L. Brilland, T. Jouan, S. Ferre, M. Carras, M. Brun, D. Mechin, J.-L. Adam, J. Troles, , Optics Express, 24 (2016) 7977-7986.
Mid-Infrared (mid-IR) spectral range, spanning from 2 μm to 20 μm, is ideal for chemical sensing using spectroscopy thanks to the presence of vibrational absorption bands of many liquid and gas substances in this wavelength range. Indeed, mid-IR spectroscopy allows simultaneous qualitative and quantitative analysis by, respectively, identifying molecules from their spectral signature and relating the concentrations of different chemical agents to their absorption coefficient according to Beer-Lambert law. In the last years, photonic integrated sensors based on mid-IR spectroscopy have emerged as a cheap, accurate, and compact solution that would enable continuous real-time on-site diagnostics and monitoring of molecular species without the need to collect samples for off-site measurements. Here, we report the design, processing and characterization of a photonic integrated transducer based on selenide ridge waveguides. Evanescent wave detection of chemical substances in liquid phase (isopropyl alcohol, C3H8O, and acetic acid, C2H4O2, both dissolved in cyclohexane) is presented using their absorption at a wavelength of 7.7 μm.
Development of Mid-infrared sensors for the detection of biochemical molecules is a challenge of great importance. Mid-infrared range (4000 – 400 cm-1) contains the absorption bands related to the vibrations of organic molecules (nitrates, hydrocarbons, pesticides, etc.). Chalcogenide glasses are an important class of amorphous materials appropriate for sensing applications. Indeed, they are mainly studied and used for their wide transparency in the infrared range (up to 15 μm for selenide glasses) and high refractive index (between 2 and 3). The aim of this study is to synthesize and characterize chalcogenide thin films for developing mid-IR optical waveguides. Therefore, two (GeSe2)100-x(Sb2Se3)x chalcogenide glasses, where x=10 and 50 were chosen for their good mid-IR transparency, high stability against crystallization and their refractive index contrast suitable for mid-IR waveguiding. Chalcogenide glasses were prepared using the conventional melting and quenching method and then used for RF magnetron sputtering deposition. Sputtered thin films were characterized in order to determine dispersion of refractive index in UV-Vis-NIR-MIR. Obtained results were used for the simulation of the optical design in mid-infrared (λ = 7.7 μm). Selenide ridge waveguide were prepared by RIE-ICP dry etching process. Single-mode propagation at 7.7 μm was observed. Optical losses of 0.7 ± 0.3 and 2.5 ± 0.1 dB.cm-1 were measured in near-infrared (λ = 1.55 μm) and midinfrared (λ = 7.7 μm), respectively. Achieved results are promising for the fabrication of an integrated optical sensor operating in the mid-infrared.
The Nd3+-doped Silicon Rich Silicon Oxide (SRSO) layers were elaborated by reactive magnetron cosputtering.
We report on refractive index measurements of Nd3+-doped SRSO layers obtained by both m-lines method
and reflectance spectroscopy. From these measurements, the Si volume fraction and also the Nd3+-doped SRSO index
dispersion were deduced by using the Bruggeman model. At 1.06 μm, work wavelength, Nd3+-doped SRSO refractive
index was equal to 1.543 corresponding to a Si volume fraction of 6.5%.
Optical losses measurements were performed on these waveguides at different wavelengths and were about 0.3 dB/cm at
1.55 μm and 1 dB/cm at 1.06 μm. Measurements are confirmed by theoretical models showing that the losses are
essentially attributed to surface scattering.
Guided fluorescence by top pumping at 488 nm on planar waveguides was studied as a function of the distance
between the excitation area and the output of the waveguide and also as a function of the pump power. The guided
fluorescence at 945 and 1100 nm was observed until 4mm of the output of the waveguide and, of course, decreased when
the excitation area moved away from the output. The fluorescence intensity increased linearly for low pump power and
this linear increasing of the guided fluorescence of Nd3+ excited by a non resonant excitation at 488 nm confirms the
strong coupling between the Si- nanoparticles and rare earth ions.
Due to remarkable properties of the chalcogenide glasses (Chgs), especially sulphide glasses, amorphous chalcogenide films should play a motivating role in the development of integrated planar optical circuits and their components. This paper describes the fabrication and properties of optical waveguides of undoped and erbium doped
sulphide films obtained by RF magnetron sputtering and laser ablation (PLD). The deposition parameters were adjusted to obtain, from sulphide glass targets with a careful control of their purity, layers with appropriate compositional, morphological, structural characteristics and optical properties. A transmission loss of 0.8 dB/cm can be obtained for rib waveguides produced by dry etching under CF4 plasma (4-300 μm wide, 5.5 μm film thickness, 1.5 μm etched thickness). The photo-luminescence of erbium doped Ge20Ga5Sb10S65 films were clearly observed in the n-IR and mid-IR spectral domain. The study of their decay lifetime with a well adapted annealing treatment controlling the roughness variation reached value of the bulk counterpart. Amplification tests were carried out leading to a complete characterisation of the Erbium doped waveguide. Gain on/off of 4.4 dB (3.4 dB/cm) were achieved for a signal at 1.54
μm in multiple modes sulphide:Er waveguides. The first demonstration of photoluminescence in mid-IR in an Er3+- doped Chg waveguide could potentially be employed to produce sources or amplifiers operating in the mid-IR.
Among the measures to reduce CO2 emissions, capture and geological storage holds out promise for the future in the
fight against climate change. The aim of this project is to develop a remote optical sensor working in the mid-infrared
range which will be able to detect and monitor carbon dioxide gas. Thus, chalcogenide glasses, transmitting light in the
1-6 μm range, are matchless materials. The first of our optical device is based on the use of two GeSe4 chalcogenide
optical fibers, connected to an FTIR spectrometer and where CO2 gas can flow freely through a 4 mm-spacing between
fibers. Such sensor system is fully reversible and the sensitivity threshold is about 0.5 vol.%. Fiber Evanescent Wave
Spectroscopy technology was also studied using a microstructured chalcogenide fiber and first tests led at 4.2 μm have
provided very promising results. Finally, in order to explore the potentiality of integrated optical structures for microsensor,
sulphide or selenide Ge25Sb10S(Se)65 rib waveguide were deposited on Si/SiO2 wafer substrates, using pulsed
laser deposition and RF magnetron sputtering deposition methods. The final aim of this study is to develop a rib
waveguide adapted for middle-IR including an Y-splitter with a reference beam and sensor beam targeting an accurate
Due to remarkable properties of the chalcogenide glasses, especially sulphide glasses, amorphous chalcogenide films
should play a motivating role in the development of integrated planar optical circuits and their components. This paper
describes the fabrication and properties of optical waveguides of pure and rare earth doped sulphide glass films prepared
by two complementary techniques: RF magnetron sputtering and pulsed laser deposition (PLD). The deposition
parameters were adjusted to obtain, from sulphide glass targets with a careful control of their purity, layers with
appropriate compositional, morphological, structural characteristics and optical properties. These films have been
characterized by micro-Raman spectroscopy, atomic force microscopy (AFM), X-ray diffraction technique (XRD) and
scanning electron microscopy (SEM) coupled with energy dispersive X-ray measurements (EDX). Their optical
properties were measured thanks to m-lines prism coupling and near field methods. Rib waveguides were produced by
dry etching under CF4, CHF3 and SF6 atmosphere. The photo-luminescence of rare earth doped GeGaSbS films were
clearly observed in the n-IR spectral domain and the study of their decay lifetime will be presented. First tests were
carried out to functionalise the films with the aim of using them as sensor.
A planar optical waveguide is manufactured by the functionnalisation of oxidised mesoporous silicon with Bromothymol Blue to achieve a sensitive ammonia sensor suitable for low gas concentrations. The propagated light intensity is measured at the output of the waveguide. The sensitivity at low concentrations and the short time of reaction of the sensor are enhanced by a confinement effect of the gas molecules inside the pores. The dependence of the output signal with gas concentration is demonstrated. When the ammonia flow is stopped, the reversibility of the initial characteristics of the propagated light is naturally obtained with the disappearance of the gas molecules.