Conventionally, LCoS, μ-LEDs, and LBS are the principal micro-displays used in Near-Eye displays. We propose an alternative display concept, which offers increased flexibility for its integration with the optical combiner, resulting in a more efficient energy yield. The concept is based on photonic integrated circuits (PIC) in the visible range, active light extraction components using liquid crystals, and pixelated holograms. The combination of these elements enables the generation of an emissive point, whose properties: position, emission angle, and divergence are adjustable. We describe our concept and compare the expected performances with conventional solutions.
Integrated photonics on glass offers advantages for sensing applications because of its relative low cost and its detection sensitivity. In this paper we discuss the design, fabrication and characterization of a micro device for sorting and sensing dielectric microparticles. The target application is the analysis of bacteria used as sentinel for water pollution. The sorting function, that does not include any functionalization layer, is done by means of dielectrophoretic forces. They are induced by castellated electrodes fed by a low frequency electric signal. The sensing function is obtained by a surface waveguide that is perturbed by the particles collected on top of it by dielectrophoresis. We first discuss the co-integration of the castellated electrodes with an optical waveguide. An efficient interaction of polystyrene beads with the guided light (up to 50% of intensity modulation) is then simulated and observed experimentally. We also showed that this multiphysics device can be used as a sensor, presenting curves of the intensity modulation depending on the concentration of beads. The attenuation in the optical signal varies between 2 and 5 dB with particle concentrations ranging from 136 to 455 beads per μL in the analyte.
Near-eye displays have become a technology of high interest for Augmented, Virtual and Mixed reality due to the unique immersive experience they provide to the user. The majority of these devices use macroscopic optical elements that make them bulky and heavy. Our team has proposed a disruptive near-eye display concept that uses the self-focusing effect to project an image to the user’s retina. To form an image, emissive points are generated from a dense photonic integrated circuit embedded within the lens of a pair of smart glasses. In this work, we present the design of a dense routing architecture that addresses thousands of randomly distributed emissive points from a few hundred inputs. The circuit combines unbalanced waveguide splitter trees with a non-periodical addressing onto a dense waveguide network. We present the design optimization through numerical simulations and estimate the overall device performance based on simulation results. A waveguide interlayer crossing simulation indicates losses better than 0.003 dB/crossing, which guarantees low optical losses over thousands of crossings. By unbalancing correctly the splitter trees, we can obtain homogeneous power profiles over an emissive point distribution. The experimental validation of our design will be a major step towards the elaboration of a first prototype.
We are developing a non-conventional retinal projector for augmented reality (AR) applications. In our concept, light at λ = 532 nm is guided in silicon-nitride (SiN) photonic integrated circuits (PICs) embedded in the lens of a pair of glasses. We use holographic elements to transmit the emissive points towards the user’s retina without using lenses. Pixels are formed in the eye using the self-focusing effect and the eye lens. The transparency of the device is an absolute requirement for our application. In this work, we present the fabrication and the characterization of our latest SiN PICs on transparent substrate. The device was fabricated by transferring the SiN PICs from a silicon to a glass substrate. We characterized the PICs and the free-space optical transmission properties of our device using in-house goniometers and a Modulation Transfer Function (MTF) setup. We found a 76% transparency at our wavelength and no image alteration. However, we measured significant waveguide propagation losses; solutions are discussed to tackle this problem. Our glass-substrate device is a major step towards a future prototype for our AR retinal projector.
Water quality monitoring faces technological challenges such as rapid and in-situ measurements, using reusable, compact and easy-to-clean devices. Glass integrated photonics is an attractive solution: it exhibits a high sensitivity to absorption or interferometric measurements, and glass is chemically compatible with aqueous environments. An innovative idea for pollution detection is to assess the bacterial cellular viability as a global indicator for pollutant toxicity. This study proposes an original concept of integrated opto-fluidic sensor which sorts and quantifies the dead or alive bacteria in a liquid sample. To ensure a robust label-free detection, the cells discrimination is provided by a selective trapping of the bacteria exploiting dielectrophoretic effects. This avoids the use of a functionalization layer. The device comprises a photonic circuit made by silver-sodium ion-exchange on glass. The sensing area co-integrates a single-mode waveguide and aluminum electrodes designed to generate dielectrophoretic forces. Both waveguide and electrodes can be encapsulated inside a polydimethylsiloxane microfluidic channel for the flow of the bacterial suspensions. In this study, charged polystyrene beads (Sigma-Aldrich, CLB9) dispersed in deionized water have been used to model dead bacteria. We observed an intensity modulation of the guided light (up to 8% of the output power) at a wavelength of 1550 nm, by selectively controlling the beads trapping. We also correlated the beads collection by microscopy imaging.
Astrophysical key programs such as exoplanet detection, young stars accretion disk and active galactic nuclei imaging require high angular resolution capability. Today, optical long baseline interferometers are the only instruments to allow such resolutions.
This paper deals with an experimental non-destructive technique for the measurement of polarization behavior of integrated optical waveguides. It is based on a high resolution polarimeter associated to an ellipsometric-type calibration which allows determining the full state of polarization of the output light. A magneto-optic perturbation is also added to generate TE/TM mode beating, whose spatial period is directly linked to the modal TE/TM birefringence. This equipment is first qualified by the measurement of modal birefringence in totally or partially buried ion exchanged waveguides. The results show that the value of the birefringence varies as a function of the diffusion aperture width or with the burying depth. By adding a magneto-optical cover layer, consisting in magnetic nanoparticles doped silica matrix obtained by a sol gel process 1, we evidence a huge increase of the beating magnitude and a decrease of the modal birefringence.
The fabrication of on-chip optical isolators to protect integrated optical sources is one of the major challenges of research in integrated optics. Their operation principle is based on the control of the guided-wave polarization and the most common structures are composed of a polarization splitter, a non-reciprocal rotator based on the Faraday effect, and a reciprocal rotator. The reciprocal rotator is a device that rotates the wave polarization by 45°. This can be achieved by creating a relative phase shift between the waveguide’s two polarization eigen states or by twisting its optics axis thanks to an appropriate shaping of its core. In this work, we propose the design and simulation of a waveguide with optics axes tilted by 45° fabricated by two cascaded field-assisted ion exchanges on a glass substrate and an encapsulation. The dependences of the proposed design on process time, temperature, applied voltage and photolithography over-etching are investigated. The final device exhibits a 45.1° rotation of its optical axes and less than 5% variation on the C+L telecommunication band.
A fully static OCT device is proposed. The glass integrated optic technology is used to have a large Fourier interferogram along an edge of the glass chip bonded on CCD linear detector array without protective glass window. After having described the system principles, first measurements will be presented. For that an optical signal coming from a SLED is divided in two equal parts injected respectively in a reference input and a probe input. It will be demonstrated that an optical phase difference measurement close to 600µm in the air can be achieved with an optical contrast of 30dB.
The integration of magneto-optical materials to realize non-reciprocal functions is still a difficult problem, because
classical magneto-optical materials require an annealing temperature as high as 700°C. In this framework, this study
shows how it is possible to realize efficient magneto-optical mode converter using the association of a magnetic
nanoparticles silica/zirconia composite with an ion-exchanged glass waveguide.
Using a sol gel process, a silica/zirconia matrix is doped by magnetic nanoparticles (CoFe2O4) and coated on a glass
substrate containing straight channel waveguides made by a silver/sodium ion exchange. The extremities of the guides
were previously buried using electric field-assisted burial in order to facilitate light injection. Soft annealing (90°C) and
UV treatment, both compatible with the ion exchange process, have been implemented to finalize the magneto-optical
film.
Depending on the amount of nanoparticles in the composite, on the spatial distribution of the field in the guide and on the
modal birefringence of the hybrid structure, the TE-TM conversion varies from several degrees to several tens of
degrees.
We propose and demonstrate a new integrated polarization splitter made by ion exchange on glass operating at a wavelength of 1.55 μm. The design is based on an asymmetric Y-junction with one output branch supporting only the TE mode. Cross-talk lower than -30.0 dB in TM mode has been achieved over a wavelength range of 80 nm. Values lower than -10.0 dB for the TE mode were demonstrated over the same bandwidth with an optimum of -19.8 dB at 1.54 μm. The experimental results are in good agreement with simulations. We measured insertion losses of 6.5 dB in both modes.
High power single-mode pump laser diodes operating around 980nm are key components for Erbium-doped
devices. Much effort is still currently devoted to improve both their wavelength stability and their achievable
output power, while maintaining a stable single-mode operation.
Usually, the emission wavelength is stabilized by an external Fiber Bragg Grating (FBG). This configuration
requires free-space optics between the laser diode output facet and the fiber or a lensed fiber to ensure an
efficient coupling efficiency. This constraint increases fabrication costs, dimensions and mechanical instabilities.
Moreover, the maximum achievable output power is limited because a high optical power density can damage
the laser facets. To increase the achievable output power, a solution consists in using Broad-Area Laser Diodes
(BALD), which are multimode emitters that are composed of large active ribbons with width of some hundreds
of micrometers. The objective is then to improve the beam quality by locking the BALD emission on its
transverse fundamental mode. We propose in this article to insert an integrated adiabatic transition between the
multimode laser and a single-mode FBG. This taper, made by ion-exchange in glass, provides a coupling
efficiency of -22.0dB from the multimode laser emission to the single-mode fiber. An optical feedback of -34dB
demonstrates the stabilization of the BALD spectrum at the Bragg wavelength. The spectrum of the device is
characterized by a maximum side-mode suppression ratio of 35dB, a RMS spectral width of (0.16 ± 0.04) nm
and a frequency shift with current of -12GHz/100mA.
The integration of magneto-optical materials with classical technologies being still a difficult problem, this study
explores the possibility to realize a mode converter based on a hybrid structure. A composite magneto-optical layer made
of a silica/zirconia matrix doped by magnetic nanoparticles is coated on the top face of ion-exchanged glass waveguides.
Optical characterizations that have been carried out demonstrated the efficiency of these hybrid structures in terms of
lateral confinement. Furthermore, TE to TM mode conversion has been observed when a longitudinal magnetic field is
applied to the device. The amount of this conversion is analysed taking into account the magneto-optical confinement
and the modal birefringence of the structure.
To overcome the difficult problem of the integration of magneto-optical materials with classical technologies, our group
has developped a composite magneto-optical material made of a hybrid organic-inorganic silica type matrix doped by
magnetic nanoparticles. Thin films of this material are obtained through a soft chemistry sol-gel process which gives a
full compatibility with an integration on glass substarte. Due to an interesting magneto optical activity (Faraday rotation
of 310°/cm) several magneto-optical functionnalities have been realized. A thin film of such composite material coated
on a pyrex™ substrate acts as non-reciprocal TE/TM mode converter. An hybrid stucture made of a composite film
coated on an ion-exchanged glass waveguide has been realized with a good propagation of light through a hybrid mode.
Finally, the sol gel process has been adapted in order to obtain 3D inverse opals which should behave as magnetophotonic
crystals. Transmittance curves reveal the photonic band gap of such opals doped with magnetic nanoparticles.
Ion-exchanged devices on glass have been successfully used to realize passive and active integrated optic devices for sensor and telecom applications. Nowadays, research is focused on the reduction of the chip dimensions with an increase of the number of different function integrated. In this paper we present how the use of two stacked optical layers can allow realizing efficient and compact pump duplexer for ion-exchanged hybrid erbium doped waveguide amplifier. Indeed our complete theoretical study of the device shows that excess losses lower than - 0.1 dB and crosstalk lower than -20 dB can be achieved.
Ion-exchange technology on glass has been successfully used for more than twenty years to manufacture dependable and
low cost integrated optics active and passive devices on silicate or phosphate glasses substrates in the telecommunication
wavelengths operation range (from λ = 0.8 to 1.7 μm). However, the recent developments of integrated optics
instruments for astronomical interferometers or biological sensors have lead to an increase of the devices operation range
towards the mid-infrared. For these reasons, we present in this paper the realization of both surface and buried
waveguides by means of ion-exchange on a glass which is transparent until λ = 5 μm. In this study, the choice of
germanate glass BGA-G115 from Kigre Inc. has been made because of both its similarity with silicate glass, its content
of Na+ ions and its excellent transparency in the considered operation range. A complete study of the silver ion diffusion
on this new glass matrix has been performed allowing the determination of silver and sodium ion-diffusion coefficients
at working temperature and silver concentration. Using theses data, simulations have shown that an ion-exchange of
90 min in a 0.03AgNO3-0.97NaNO3 molten salt at a temperature of 330°C can lead to the realization of surface single
mode channel waveguides at either λ = 1.55 μm or λ = 3.39 μm depending on the diffusion window width. To
demonstrate channel waveguides on BGA-G115, a specific technological process based on the deposition of a
polycrystalline silicon masking layer has been implemented. Single-mode channel waveguides, with a 2.5 μm diffusion
window width, have thus been realized and characterized at the wavelength of 1.55 m. Modal size has been measured to
be 10 μm ± 1 μm x 7 μm ± 1 μm for propagation losses of 1.2 dB/cm ± 0.5 dB/cm for a 2 cm ± 0.1 cm long device. As
for buried waveguides, their feasibility has been demonstrated on multimode ones where a burying depth of 25 μm ± 2
μm has been measured.
Ion-exchange on glass has been successfully used for more than twenty years to realize integrated optics devices such as
wavelength multiplexers, splitters, optical amplifiers, lasers or sensors. One of the major issue is today to integrate more
functions on a single chip which is usually realized be reducing the dimensions of the waveguides. Nonetheless this
reduction is intrinsically limited by the maximum index variation achievable. For this reason, we propose and investigate
in this article the realization of 3D structures where waveguides are integrated vertically instead of horizontally. Based
on the selective burial of ion-exchanged waveguides and the cascading of multiple ion-exchanges, the realization of
"vertical" asymmetric and symmetric Y-junctions have been investigated theoretically.
Broadband wavelength (de)multiplexers play a key role in different fields of integrated optics. In particular, the development of Erbium Doped Waveguide Amplifiers (EDWA) requires efficient integrated pump/signal multiplexers. In this article, the design and the realization of a 980 nm/1550 nm wavelength multiplexer based on a segmented asymmetric Y junction made by silver/sodium ion exchange on glass is discussed. We first present the behavior of an asymmetric Y junction, in order to describe its use as a wavelength (de)multiplexer. Then, the index averaging principle of a segmented waveguide is detailed, as well as its application in the design of one of the asymmetric Y junction branches. The design of a segmented asymmetric Y junction is then described, as well as its BPM simulations results. They show isolation of 33 dB at 980 nm and 25.6 dB at 1550 nm with excess losses of 2.6 dB at 980 nm and 1.3 dB at 1550 nm. In a second time, we present the realization of this component using a Silver/Sodium ion-exchange on glass. For λ = 980 nm, the isolation measured is (31 ± 1) dB, and in the third communication window, the isolation increases from (11.5±0.25) dB at λ = 1500 nm to (15.5±0.25) dB at λ = 1600 nm. The broadband operation is only limited by the modal characteristics of the waveguides composing the junction and ranges from 1500 nm to 1650 nm. Total insertion losses measured at 980nm are (2.63±0.1) dB. Around 1550 nm, losses vary from (3.6 ± 0.1) dB at the 1500 nm wavelength to (4.6 ± 0.1) dB at 1600 nm.
In this paper, the realization and characterization of periodic segmented waveguides made by ion-exchange on glass is presented as well as their application to polarizers and wavelength duplexers. Segmented waveguides are of major interest for integrated devices because they allow tailoring the refractive index without changing the technological parameters. Indeed, a segmented waveguide, which is composed of a periodic succession of guiding and non-guiding zones, can be considered as a classical waveguide with a core refractive index that ranges from the segmented core to the substrate ones, depending on the segmentation ratio. Through this way, it is thus possible to avoid the use of more complex techniques that require a double-step lithography process.
In the first part of the article, surface segmented waveguides made by ion-exchange on glass are studied and a linear relationship between the segmentation duty cycle and the maximum core refractive index of an equivalent continous waveguide is demonstrated.
A simple correction on the duty cycle is needed to take into account the longitudinal diffusion.
After a presentation of its principle of operation, in the second part of the article, we propose the realization and characterization by means of segmented waveguide of a polarizer with more than 30dB of extinction ratio at λ=1550nm. Finally, the design and first results obtained on a duplexer based on an asymmetric segmented Y-junction are presented.
We present the design of an innovating integrated planar structure adapted for intensity or phase measurements. It is based on the evanescent prism decoupling of the optical signal from a waveguide used as the sensing element. The device is formed by successive thin film sputtering deposition. A TiO2 crystalline layer forms the gas sensing element from which light is coupled out by a planar high refractive index prism. We experimentally validate the structure.
These last years, the growth of data traffic has increased the interest for broadband integrated optic devices. Their applications include, for example, the fiber communications on a single fiber by adding the transmission capacity of two optical telecommunication windows for Local Area Networks (LAN) and Wide Area Networks (WAN) or by combining pump and signal wavelenghts in rare earth doped intergrated optical amplifiers. A promising technology to realize those devices is ion-exchange on glass. Indeed, it allows the integration of different functions in a glass substrate with efficient results and a better compatibility in fiber systems with a low cost. We propose in this paper an original broadband duplexer based on a leaky structure. First, the physical principle of the component is explained. The core of the structure is a leaky zone which involves a non-resonant coupling and ensures a broadband spectral behavior to the component. Then, the broadband duplexer is presented and the focus is specially made on the improvement of the outputs crosstalk through the suppression of parasitical back reflections. Theoretical optimization and validation by simulations are presented. Finally, perspectives of this work are proposed.
With the increase of optical communications bit rate, the interest for broad-band integrated optic Wavelength Demultiplexers Multiplexers (WDM) devices is growing. Their applications include, for example, the fiber communications on a single fiber by adding the transmission capacity of both optical telecommunication windows at the wavelengths 1.31μm and 1.55μm. They also achieve to combine pump and signal wavelengths in rare earth doped integrated optical amplifiers and lasers. A promising technology to realize those devices is ion-exchange on glass which allows the integration of different functions in a glass substrate with efficient results and an excellent compatibility with fiber systems. In this paper, an original design of a broad-band duplexer is presented. The principle of the device is first explained. Then numerical and experimental results confirming good performances are shown. Instead of using phase-matched coupling as it is usually done, we propose a structure based on distributed coupling. This particularity entails a low sensitivity to technological parameters and a broad-band behavior. As a validation, a test device has been realized by ion-exchange on glass.
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