Elise Ghibaudo

Realization of a 980-nm/1550-nm Pump-Signal (De)multiplexer Made by Ion-Exchange on Glass Using a Segmented Asymmetric Y-Junction

In this letter, the fabrication and characterization of a broadband 980-nm/1550-nm wavelength (de)multiplexer is described. This device is adapted for pump/signal multiplexing in erbium-doped waveguide amplifiers. The structure chosen is a segmented asymmetric Y-junction, which can be fabricated with one masking level using silver-sodium ion-exchange on a silicate glass substrate. The nonresonant behavior of the Y-junction allows a wideband multiplexing with isolations increasing from (9.7plusmn0.1) dB at 1500 nm to (15plusmn0.1) dB at 1630 nm and (26plusmn1) dB at 980 nm. The total insertion losses are (2.8plusmn0.1) dB at 980 nm and (3.3plusmn0.2) dB between 1500 and 1630 nm

Vertically Integrated Broadband Duplexer for Erbium-Doped Waveguide Amplifiers Made by Ion Exchange on Glass

The hybrid integration of optical amplifier modules requires the development of a new kind of pump/signal duplexers. In this letter, a new structure highly compatible with pump diode waveguides (λ = 0.98 μm), optical fibers (λ = 1.55 μm), and hybrid erbium-doped waveguide amplifiers is proposed. The device, based on a vertically integrated asymmetric Y-junction, has been realized by cascading three ion exchanges on a glass substrate. Bandwidth of more than 200 nm around the two working wavelengths has been demonstrated with isolations between the two outputs reaching (21 ± 0.4) dB at λ = 0.98 μm and (44 ± 0.4) dB at λ = 1.55 μm and low losses.

Birefringence Measurements in Optical Waveguides

This paper deals with an experimental nondestructive technique for the measurement of modal birefringence of integrated optical waveguides. The method is based on a magneto-optical perturbation technique combined with a highly sensitive polarimeter. Magneto-optical modal conversion, through the Verdet constant of the waveguides, and its dependence on the perturbation length are discussed. In this paper, the practical application of this equipment is proposed for the measurement of modal birefringence in totally or partially buried ion exchanged waveguides.

980nm-1550nm vertically integrated duplexer for hybrid erbium- doped waveguide amplifiers on glass

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.

Broad-area laser diode with stable single-mode output and wavelength stabilization

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.

Fully compatible magneto-optical sol-gel material with glass waveguides technologies: application to mode converters

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.

Efficient magneto-optical mode converter on glass

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.

Optical properties of TiO2-x thin films studied by spectroscopic ellipsometry: substrate temperature effect

Titanium oxide thin films were obtained by reactive dc-magnetron sputtering. A target of titanium (Lesker; 99.9% pure) and a mixture of argon and oxygen gases were used to deposit titanium oxide films onto silicon and glass substrates. The substrate temperature was varied between 200 and 400°C. Optical constants have been determined by spectroscopic ellipsometry and by using the optical transmittance data from UV-Vis spectrometry. The effect of substrate temperature on the optical properties is analyzed. Results indicate an increase in the refractive index of the films with substrate temperature, which is attributed to changes in the oxygen content, density and degree of crystallization of the films.

Birefringence measurement of glass ion-exchanged waveguides: burying depth or cover layer influence

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.

Design of a waveguide with optics axes tilted by 45° and realized by ion-exchange on glass

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.