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The success of glass photonics are many, with a large spectrum of applications covering Information and Communication Technology, Health and Biology, Structural Engineering, and Environment Monitoring Systems, etc. A paradigmatic example is the development of the Erbium-Doped Fiber Amplifier (EDFA) allowing the raise of optical telecommunications and high speed internet. Silica glass is the most common glass used for photonics applications. However, certain of its characteristics may be detrimental for luminescence properties (low rare-earth solubility, high phonon energy, etc). To overcome these limitations, the use of nanoparticles in optical waveguides has gained large interest in modern photonic technology nowadays. Such waveguides would combine the advantages of silica (transparency, cost, chemical and mechanical durability, etc.) and the specific properties provided by the nanoparticles which encapsulate the rare-earth ions. In this paper, we discuss on the opportunities offered by the nanoparticles addition in glasses for lasers and amplifiers thanks to the engineering of the spectroscopic properties. We present also an emerging application: sensors based on high scattered fibers.

Rare earth doped phosphate glasses are attractive materials for the engineering of photonic devices, due to their easy processing, good thermal stability, excellent optical properties and high rare-earth ions solubility [1]. Besides, phosphate glasses with a P 2 O 5 content of 50 mol% have been shown to be suitable for fiber drawing. It is well known that if the rare-earth ions are located in crystalline phase of desired nature and structure, the spectroscopic properties of the glasses can be enhanced [2]. Therefore, efforts have been focused on the development of new glass-ceramics (GCS) obtained from the heat treatment of glasses, as these engineered materials possess some of the glass properties (large flexibility of composition and geometry) but also some advantages of the RE-doped single crystals (high absorption and emission as well as long lifetimes).

In this paper we discuss recent progress in exploring short-term and long-term stability of high power Yb-doped fiber lasers and amplifiers. Long-term stability is associated with photodarkening effects that can significantly reduce operational lifetime of a high-power laser system. Short-term stability is associated with so-called transverse modal instabilities that degrade output beam quality at average powers above a certain threshold. In this paper we review ongoing studies that provide experimental characterization, and explore physical causes and mitigation strategies of the different physical phenomena involved. Those studies are critical for achieving stable operation of high power fiber lasers.

An introduction is provided to the feature issue of Optical Materials Express on Optical Fiber Materials.

International audience; We demonstrate super-broad luminescence over 70 nm of bandwidth and spectral hole-burning effect obtained in just a few cm of novel air-clad, highly concentrated Er/Yb-doped phosphate fiber. The fiber is drawn from preforms of glasses within the P2O5 - SrO - Na2O composition. The fabrication process, thermal, structural, and optical properties of the fiber are described. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

International audience; Applications involving optical fibers have grown considerably in recent years with intense levels of research having been focused on the development of not only new generations of optical fiber materials and designs, but also on new processes for their preparation. In this paper, we review the latest developments in advanced materials for optical fibers ranging from silica, to semi-conductors, to particle-containing glasses, to chalcogenides and also in process-related innovations.

In Part I of this study a coupled thermo-mechanical finite element model for the simulation of the entire precision glass lens molding process was presented. That study addressed the material definitions for the molding glass, L-BAL35, computational convergence, and how the final deviation of the lens shape from the mold shape is achieved for both a bi-convex lens and a steep meniscus lens. In the current study, after validating the computational approach for both lens types, an extensive sensitivity analysis is performed to quantify the importance of several material and process parameters that affect deviation for both lens shapes. Such a computational mechanics approach has the potential to replace the current trial-and-error, iterative process of mold profile design to produce glass optics of required geometry, provided all the input parameters are known to sufficient accuracy. Some of the critical contributors to deviation include structural relaxation of the glass, thermal expansion of the molds, TR...

Coupled thermomechanical finite element models were developed in ABAQUS to simulate the precision glass lens molding process, including the stages of heating, soaking, pressing, cooling and release. The aim of the models was the prediction of the deviation of the final lens profile from that of the mold, which was accomplished to within one-half of a micron. The molding glass was modeled as viscoelastic in shear and volume using an n-term, prony series; temperature dependence of the material behavior was taken into account using the assumption of thermal rheological simplicity (TRS); structural relaxation as described by the Tool-Narayanaswamy-Moynihan (TNM)-model was used to account for temperature history dependent expansion and contraction, and the molds were modeled as elastic taking into account both mechanical and thermal strain. In Part I of this two-part series, the computational approach and material definitions are presented. Furthermore, in preparation for the sensitivity analysis presented in ...

The mid-infrared (mid-IR, 2 to 10 μm) is a technologically important spectral regime for sensing, imaging, and communications. In the past few years, there has been a surge of interest in novel mid-IR optical materials as well as their device implementations to address the increasing demands from these applications. The 22 papers in this feature issue represent a diverse cross-section of the latest technological advances in this field, spanning mid-IR light generation, propagation, manipulation, and detection functions in free-space, fiber, and planar platforms. In terms of material systems, semiconductors, glasses, plasmonic metals, as well as nanostructures specifically engineered for the mid-IR band, are all extensively covered. We hope that the readers will enjoy the kaleidoscopic view of the burgeoning field of mid-IR optics and photonics through this feature issue.

In this paper, we review ongoing progress in the development of novel on-chip, low loss planar molecular sensors that address the emerging need in the field of biochemical sensing. Chalcogenide glasses were identified as the material of choice for sensing due to their wide infrared transparency window. We report the details of manufacturing processes used to realize novel high-index-contrast, compact micro-disk resonators. Our findings demonstrate that our device can operate in dual modalities, for detection of the infrared optical absorption of a binding event using cavity enhanced spectroscopy, or sensing refractive index change due to surface molecular binding and extracting micro-structural evolution information via cavity enhanced refractometry.

Planar microdisk optical resonators fabricated from Ge23Sb7S70 chalcogenide glass on a silicon substrate are applied for cavity-enhanced spectroscopic measurement of chemical molecular absorption fingerprint. A 0.02 cm- 1 detection limit for these devices is demonstrated. This detection limit represents a threefold improvement as compared to a straight waveguide sensor, while the physical device length is reduced by 40-fold. The reduction in device footprint with enhanced sensitivity makes the structure attractive for ldquosensor-on-a-chiprdquo device applications. We also present a design optimization approach for cavity-enhanced IR absorption spectroscopy using traveling-wave resonators, which indicates that further performance improvement can be achieved in optimally coupled, low-loss resonant cavities.

In this paper, we report results of a systematic study to evaluate the relationship between compositional variation and the photo-response of Gallium containing sulfo-selenide glasses upon IR femtosecond laser exposure. We show that IR femtosecond laser irradiation in this system results in near-surface photo-expansion, which based on micro-Raman spectroscopy, has been related to an increased connection of GeS 4 units to form corner sharing GeS 4/2 units with a concurrent formation of S–S bridges. The lower surface photo-expansion of the Ga- containing sulfide and sulfo-selenide glasses compared to that of the Ga-free sulfide and sulfo-selenide glasses has been related to the presence of GaS 4 and Se–Se isolated units in the germanate glass network which are expected to restrict the connection between GeS 4 units during laser exposure. Such mechanistic understanding of material modification opens the pathway towards the laser writing of active photonic devices in the near-surface of these glasses.

Waveguides from thermally evaporated Ge 23 Sb 7 S 70 films have been fabricated using both plasma etching and lift-off techniques. The two methods have been compared in their ability to provide high quality, low-loss waveguides for microphotonics applications. We have demonstrated in this paper that low-loss 3 μm and 4 μm wide channel waveguides can be fabricated using CHF 3 and SF 6 plasma etching, and lift-off, respectively. Additionally, lift-off does not change the structure of the waveguide during the fabrication whereas the structure of the plasma etched waveguide differs slightly from that of the films. Finally, channel waveguides fabricated using lift-off leads to a low RMS roughness of 10 ± 2 nm, compared to those fabricated by a plasma etching process which lead to a higher RMS roughness of 17–20 nm. As-fabricated waveguides have been found to exhibit optical propagation losses of 3–5 dB/cm at 1550 nm. These high losses are attributed to scattering by sidewall roughness and defects arising from the fabrication process.

This paper reviews ongoing progress in exploring the mechanistic origins of photoinduced structural modification in chalcogenide glasses (ChGs). These findings, reported by groups at the University of Central Florida, Clemson University, and throughout other research programs within the United States and abroad, have examined the relationship between the network modification and other photoresponse of IR glasses upon exposure to near-infrared (NIR) femtosecond laser exposure. Contained is a review on the principles of femtosecond laser writing in glass, the photoinduced phenomena, and a summary of the main models predicting photoinduced material response. We compare the photoresponse of As- and Ge-based films, taken as example, following NIR femtosecond laser irradiation that results in near-surface photoexpansion and an increase or decrease of the refractive index, respectively. This difference in photoresponse has been related to the "layered" network of the As-based glass that leads to the breaking and formation of bonds during laser exposure as compared to the 3-D network of Ge-based glass that leads only to a modification of the bond arrangements. Last, an explanation of the need to control the photoresponse of ChGs by aging, changing the glass thermal history, adding modifiers, or replacing the anions forming the network is discussed.

We investigate the measurement of bend losses in few-mode large-mode-area (LMA) fibers. The influence of the light source spectral characteristics, modal power content and cladding light on the measurement accuracy and precision is studied experimentally. Monte-Carlo simulations are performed to understand the distribution of the variations. This study provides practical guidelines for bend loss measurements.

We present an experimental study on mode coupling characteristics of few-mode large-mode-area (LMA) fibers, which are widely used in high power fiber lasers. The modal power allocation is measured by modal decomposition of the nearfield intensity profile of the output beam. Cut-back measurements are carried out with commonly-used fibers with different fiber geometries. The evolution of the modal power content due to mode coupling is presented. The influence of the fiber geometry on mode coupling is discussed.

Polymer multilayered nanocoating capable of concentrating various chemical substances at IR-ATR waveguide surfaces is described. The coating affinity to an analyte played a pivotal role in sensitivity enhancement of the IR-ATR measurements, since the unmodified waveguide did not show any analyte detection.

A thermal reflow technique is applied to high-index-contrast, sub-micron waveguides in As(2)S(3) chalcogenide glass to reduce the sidewall roughness and associated optical scattering loss. We show that the reflow process effectively decreases sidewall roughness of chalcogenide glass waveguides. A kinetic model is presented to quantitatively explain the sidewall roughness evolution during thermal reflow. Further, we develop a technique to calculate waveguide optical loss using the roughness evolution model, and predict the ultimate low loss limit in reflowed high-index-contrast glass waveguides. Up to 50% optical loss reduction after reflow treatment is experimentally observed, and the practical loss limiting factors are discussed.

International audience; In this paper, we report the spatially controlled dissolution of silver nanoparticles in irradiated SiO2 sol–gel films. The Ag nanoparticles have been formed in the sol–gel solution before the film deposition by adding Triton and ascorbic acid and also after the film deposition using a heat treatment at 700 °C for few minutes or at 550 °C for 6 h in reducing atmosphere. Using a spectrometer, a new view white light interferometer and a micro-thermal analyzer, we demonstrate that the silver nanoparticles can be dissolved using a continuous black ray UV lamp or with a near-infrared (NIR) femtosecond laser, due to a significantly increase in the local temperature. We confirm that the micro-thermal analyzer can be used as a new tool to study the dissolution of metallic nanoparticles in thin film if located at the surface of the films.

International audience; Amorphous chalcogenide films play a motivating role in the development of integrated planar optical circuits and their components. The aim of the present investigation was to optimize deposition conditions for preparation of pure and Tm3+ doped sulfide films by radio-frequency magnetron sputtering. The study of their composition, morphological characteristics and thermal properties was realized by scanning electronic microscope attached with energy dispersive spectroscopy, Rutherford backscattering, X-ray diffraction, and micro-thermal probe. Some optical properties, like transmission, index of refraction, optical band-gap, propagation modes from 633 to 1540 nm, were investigated on thin films. The whole results point out hopeful perspectives strengthened by the clear observation of the near-infrared photo-luminescence of Tm3+ doped sulfide films.

We demonstrate, for the first time to the best of our knowledge, low-loss, Si-CMOS-compatible fabrication of single-mode chalcogenide strip waveguides. As a novel route of chalcogenide glass film patterning, lift-off allows several benefits: leverage with Si-CMOS process compatibility; ability to fabricate single-mode waveguides with core sizes down to submicron range; and reduced sidewall roughness. High-index-contrast Ge(23)Sb(7)S(70) strip waveguides have been fabricated using lift-off with excellent uniformity of loss propagation and the lowest loss figure of reported to date. We also show that small core Ge(23)Sb(7)S(70) rib waveguides can be fabricated via lift-off as well, with loss figures lower than 0.5 dB/cm. Additionally, we find through waveguide modal analysis that although overall transmission loss is low, the predominant source of this loss comes from scattering at the sidewalls.

We have fabricated and tested, to the best of our knowledge, the first microfluidic device monolithically integrated with planar chalcogenide glass waveguides on a silicon substrate. High-quality Ge(23)Sb(7)S(70) glass films have been deposited onto oxide coated silicon wafers using thermal evaporation, and high-index-contrast channel waveguides have been defined using SF(6) plasma etching. Microfluidic channel patterning in photocurable resin (SU8) and channel sealing by a polydimethylsiloxane (PDMS) cover completed the device fabrication. The chalcogenide waveguides yield a transmission loss of 2.3 dB/cm at 1550 nm. We show in this letter that using this device, N-methylaniline can be detected using its well-defined absorption fingerprint of the N-H bond near 1496 nm. Our measurements indicate linear response of the sensor to varying N-methylaniline concentrations. From our experiments, a sensitivity of this sensor down to a N-methylaniline concentration 0.7 vol. % is expected. Given the low-cost fabrication process used, and robust device configuration, our integration scheme provides a promising device platform for chemical sensing applications.

In this paper we explore the TeO(2)-Bi(2)O(3)-BaO glass family with varied TeO(2) concentration for Raman gain applications, and we report, for the first time, the peak Raman gain coefficients of glasses within this glass family extrapolated from non-resonant absolute Raman cross-section measurements at 785 nm. Estimated Raman gain coefficients show peak values of up to 40 times higher than silica for the main TeO(2) bands. Other optical properties, including index dispersion from the visible to the long wave Infrared (LWIR) are also summarized in this paper.

Ternary chalcogenide glass films from identical parent bulk glasses were prepared by thermal evaporation (TE) and pulsed laser deposition (PLD) and subjected to 810-nm femtosecond laser exposure at both kHz and MHz repetition rates. The exposure-induced modification on the glass film's surface profile, refractive index, and structural properties were shown to be a function of laser irradiance, the number of laser pulses per focal spot, and repetition rate. Film response was shown to be related to deposition technique-related density and the number of glass bonds within the irradiated focal volume. The induced changes resulted from a reduction in glass network connectivity among GeS(4/2), GeS(4), S-S and S(3)Ge-S-GeS(3) units.

We present the microstructuring of bulk and film chalcogenide glasses using IR femtosecond laser exposure and photolithography for molecular sensing.

We demonstrate Si-CMOS-compatible lift-off fabrication of chalcogenide glass waveguides monolithically integrated on a silicon platform. As a novel route of glass film patterning, lift-off allows several benefits: leverage with Si-CMOS process compatibility; ability to fabricate single-mode waveguides with core sizes down to submicron range; reduced sidewall roughness; and wide applicability to other non-silica glass compositions. High-index-contrast (HIC) single-mode strip waveguides have been fabricated with from several glass target compositions including Ge 23 Sb 7 S 70 , As 2 S 3 , As 36 Ge 6 S 58 , As 36 Sb 6 S 58 and TeO 2 . We measured Ge-Sb-S waveguides with low loss and excellent wafer-scale uniformity. We have experimentally demonstrated propagation loss reduction via graded-index (GRIN) cladding layers in HIC glass waveguides. These efforts have shown that scattering loss arising from sidewall roughness can be significantly reduced without compromising the high-index-contrast condition by inserting thin GRIN cladding layers with refractive indices intermediate between the core and topmost cover of a strip waveguide.

International audience; Homogeneous amorphous films in the GeS2-GeO2 system have been deposited by a rf sputtering technique. Optical characterizations have shown that the cut-off wavelength and the linear indices increase with an increase in the S/O ratio. Raman spectroscopy indicates the presence of new modes that can be assigned to intermediate germanium oxysulfide structural units. Photo-sensitivity of the oxysulfide films has been demonstrated for irradiation near the band-gap. Diffraction gratings inscribed using 488 nm exposure displayed a limited diffraction efficiency (≤3%) that weakens with a corresponding decrease in the glass S/O ratio.

The nonlinear refractive index ( n 2 ) of new germanium-based sulfo-selenide glasses has been measured at 1064 nm using Z-scan technique, with picosecond pulses emitted by a 10 Hz Q-switched mode-locked Nd:Yag laser. We have determined the impact of the progressive replacement of S by Se on the nonlinear properties of these glasses. The value of n 2 strongly increases with the substitution of S by Se, up to 350 times the n 2 for fused silica. X-ray photoelectron spectroscopy (XPS) indicates that the increase of Ge–Se bond units in the glass network is responsible for the increase of n 2 . The suitability of these glasses for optical switching at telecommunication wavelengths based on such nonlinear properties has been also confirmed.

Fs MR exposure has been used to induce refractive index change in bulks in the As0.42-x-yGexSbyS0.58 system. Photo- induced Deltan has been investigated as a function of laser dose by measuring diffraction efficiency of buried gratings.

Refractive index modifications of film Ge0.23Sb0.07S0.7 induced by 800 nm femtosecond laser irradiation are studied for laser repetition rates of 1 kHz and 80 MHz. Measurements are taken using an interferometric method and analysis of the transmission spectra.

Chalcogenide glasses are an ideal material candidate for evanescent biochemical sensing due to their mid and far-infrared transparency. We have fabricated and tested, to the best of our knowledge, the first microfluidic device monolithically integrated with planar chalcogenide glass waveguides. High-index-contrast channel waveguides have been defined using plasma etching in thermally evaporated Ge23Sb7S70 films, followed by microfluidic channel patterning in photocurable resin (SU8) and channel sealing by a polydimethylsiloxane (PDMS) cover. Using this device, N-methylaniline can be detected using its well-defined absorption fingerprint of the N-H bond near 1496 nm. Our measurements indicate linear response of the sensor to varying N-methylaniline concentrations and a sensitivity of this sensor down to N-methylaniline concentration of 0.7 vol. %. Thermal reflow has been employed as an effective method to smooth chalcogenide waveguide sidewall roughness from 6.1 nm to 0.56 nm. Given the low-cost fabrication process and robust device configuration, our integration scheme provides a promising device platform for infrared chemical sensing applications.

We report n2 measurements of selected chalcogenide glasses using a modified Z-scan technique. Measurements were made with picosecond pulses emitted by a 10 Hz Q-switched, mode-locked Nd:YAG laser at 1064 nm under conditions suitable to characterize ultrafast nonlinearities. The nonlinear index increases significantly up to 246 times the n2 for fused silica with an increase of SbS3 units and also very slightly with the replacement of Ge by Ga or S by Se. We have attributed the variation of n2 to the total number of electronic lone pairs and to the position of the absorption band gap, which are induced by the presence of GaS4 units or Se-Se bonds in the glass structure.

We describe the fabrication of waveguides in optical materials using a femtosecond laser. The direct laser writing technique has the unique advantage of allowing volume structures to be fabricated. We investigate several writing schemes in non-oxide glasses and characterize the photo-induced modifications of the optical properties. These changes are linked to structural changes in the glass matrix, as revealed by Raman spectroscopy.

Rapid progress has been made in the last few years in the development direct-write, femtosecond laser micro-structuring and waveguide writing techniques in various materials, particularly semiconductor and other photo-sensitive glasses. There is considerable potential for this becoming a disruptive technology in photonic device fabrication, perhaps even leading to the development of devices that are difficult to fabricate by any other technique. We will review these developments, and with an optimistic eye, offer some perspectives on the future of this technology for opto-electronic systems.

This paper reviews ongoing progress in the design and fabrication of new, on-chip, low loss planar molecular sensors. We report the details of device design, material selection and manufacturing processes used to realise high-index-contrast (HIC), compact micro-disk resonators. These structures have been fabricated in thermally evaporated As- and Ge-based chalcogenide glass films with PDMS (polydimethylsiloxane) micro-fluidic channels using standard UV lithography. Discussed are findings that demonstrate that our novel chalcogenide-based micro-fluidic device can be used as highly sensitive refractive index sensors.

High-index-contrast compact microdisk resonators in thermally evaporated As2S3 and Ge17Sb12S71 chalcogenide glass films are designed and fabricated using standard UV lithography and characterized. Our pulley coupler configuration demonstrates coupling of the resonators to monolithically integrated photonic wire waveguides without resorting to demanding fine-line lithography. Microdisk resonators in As2S3 support whispering-gallery-mode with cavity quality factors (Q) exceeding 2 x 10(5), the highest Q value reported in resonator structures in chalcogenide glasses to the best of our knowledge. We have successfully demonstrated a lab-on-a-chip prototype sensor device with the integration of our resonator with planar microfluidic systems. The sensor shows a refractive index sensitivity of 182 nm/RIU (refractive index unit) and a wavelength resolution of 0.1 pm through a resonant peak fit. This corresponds to a refractive index detection limit of 8 x 10(-7) RIU at 1550 nm in wavelength, which could be further improved by shifting the operating wavelength to a region where water absorption is reduced.

The Raman gain spectra of millimeter thick As(2)S(3) and As(24)S(38)Se(38) glasses and Ge((23 - x))Ga(x)Sb(7)S((70 - y))Se(y) with x = 0 and 5 and y = 0, 2, 5 have been measured using a direct nonlinear optics technique. The pump light originated from a picosecond Nd:YAG laser operating at 1064 nm and a tunable optical parametric generator and amplifier (OPG/OPA) was used as a source for the probe light. A peak material Raman gain coefficient of (155 +/- 11) x 10(-13) m/W has been measured for the As(24)S(38)Se(38) glass. A reversible photodarkening effect which responds to picosecond pulses is also reported. Finally, surface optical damage threshold measurements were found to be less than 9 GW/cm(2) for the reported samples, values which are comparable to some TeO(2)-based glasses with lower nonlinearities.

This paper reviews ongoing progress in the development of novel on-chip planar molecular sensors in infrared-transparent chalcogenide glasses. We demonstrate on-chip cavity-enhanced refractometry and infrared absorption spectroscopy for sensitive detection of proteins and small molecules.

We show the possibility to control the Cu and the Au nanoparticles to precipitate/dissolve selectively in a SiO2 glass matrix using UV/TR light sources with micron resolution. The fabricated/dissolved structures have been characterized using UV-Vis-NIR spectroscopy. A micro- Thermal-analyzer has been used to verify the presence of nanoparticles in the film.

Chalcogenide glasses are widely used in device applications which capitalize on their unique linear and nonlinear optical properties, and infrared transparency. The role of the glass’ photosensitivity in device fabrication and eventual use, is discussed.

A rapid thermal reflow technique is applied to high-index-contrast, sub-micron waveguides in As 2 S 3 chalcogenide glass to reduce sidewall roughness and associated optical scattering loss. Up to 50% optical loss reduction after reflow treatment is achieved.

We demonstrate the preparation of Ge 23 Sb 7 S 70 films by spin-coating techniques with good surface and compositional homogeneity. The films exhibit a large photo-induced refractive index change, which have great potential for photonic device tuning.