Pascal Mollier

A micromachined connector for the coupling of optical waveguides and ribbon optical fibers

This paper describes in details the fabrication and tests of a micromechanical connector, which is used for the precise optical self-alignment of multi-waveguide optical integrated circuits (OIC) to ribbon optical fibers, without injecting light in the fiber. Nickel alignment pins are electrodeposited on the OIC using a photolithographic process, and these pins are inserted into suitable openings made on a silicon micromachined platform, on which optical fibers are accurately positioned using V-grooves. A simultaneous fabrication of several microstructures which are used as an assistance for the assembly of the fibers and the waveguides is presented for the first time. Design and fabrication issues are reported, as well as preliminary experimental results which show that excess optical losses on the order of 3 dB per coupling facet can be obtained.

Erbium-doped fiber laser tuning using two cascaded unbalanced Mach-Zehnder interferometers as intracavity filter: numerical analysis and experimental confirmation

We propose a new method for tuning an Er/sup 3+/-doped continuous-wave fiber-ring laser. We present a novel numerical model and confirm the model with experimental results. The numerical model relies on the implementation of the analytical solution of signal propagation over small (elemental) segments of amplifier fiber rather than using the usual Runge-Kutta algorithm. The validity of the model is verified by the good agreement between computer results and experimental data. Experiments demonstrating a 11.2-nm wavelength tuning range have been conducted using an electrooptic intracavity filter composed of two cascaded unbalanced Mach-Zehnder interferometers (MZIs) integrated in lithium niobate. The numerical analysis shows that the tuning range obtained is limited by the combination of gain shape and filter characteristics. Increased tuning range can be obtained by decreasing losses or by using a more selective filter.

Proton exchanged imbalanced Ti:LiNbO3 Mach‐Zehnder modulator

We describe the fabrication process of a LiNbO3 integrated Mach‐Zehnder interferometer featuring a large path‐imbalance between the arms. This path‐imbalance is created by the proton exchange located on one arm. The proton exchange increases the extraordinary refractive index ne of lithium niobate and modifies the effective index of the guided mode. Path‐differences of 80 μm per mm of proton exchange length are obtained with the fabrication process reported here.

A tunable mode-locked erbium-doped fibre laser using a Lyot-type tuner integrated in lithium niobate

In this paper we report the realization of a tunable erbium-doped fibre laser. The intracavity tuner is a filter composed of two cascaded unbalanced Mach-Zehnder interferometers, integrated in a single chip of lithium niobate. Wavelength tuning is achieved electro-optically over a range of 17 nm around 1540 nm. A phase modulator integrated in the same chip allows the tunable laser to operate in a mode-locked regime.

Microconnectors for the passive alignment of optical waveguides and ribbon optical fibers

This paper describes the fabrication of a new mechanical microconnector, which is used for the precise optical self-alignment of multi-waveguide Optical Integrated Circuits (OIC) to ribbon optical fibers, without injecting light in the fiber. Nickel alignment pins are electrodeposited on the OIC using a photolithographic process, and the pins are inserted into suitable openings made on a silicon micromachined platform, on which optical fibers are accurately positioned using V-grooves. Design and fabrication issues are reported, as well as preliminary experimental results which show that excess optical losses on the order of 3 dB can be obtained.

Secrecy improvement in confidential coherence modulation by means of a new keying structure

Abstract In this paper, we present a new keying structure which enhances the secrecy of an already relatively secure coherence modulation method we developed recently. The originality of the method consists in using an encrypting key composed of a large amplitude – low frequency part and a low amplitude – high frequency part. These two components ensure that the spectrum, as well as the signal tapped by an eavesdropper, are efficiently corrupted. When the key is applied simultaneously to both the encoder and the decoder, the signal is correctly restored. Both theoretical aspects and experimental confirmations are presented in this paper.

550-nm emission of erbium-doped Ti:LiNbO3 waveguide pumped at 980 nm

In this paper we demonstrate up-conversion emission at 550 nm into an Er-doped Ti:LiNbO3 waveguide pumped by a 980 nm laser diode. The two main processes of the up-conversion are the sequential two photon absorption (STPA) and the energy transfer (ET). In our case, the fluorescence lifetime of the 4S3/2 energy level of the Er3+ ion is measured as 32 microseconds. The fluorescence spectrum shows two peaks around 550 nm and 558 nm which are strongly polarization dependent. This effect is attributed to the different crystal fields induced by the location of Er3+ ions in the different LiNbO3 crystal lattices. The variations of the fluorescence intensity and the transmitted pump power are studied versus the length of Er-doped waveguide. The fluorescence intensity has a quadratic behavior versus the coupled pump power which demonstrate that the up-conversion mechanism is mainly due to a STPA process.

Mechanical clip-on and flip-chip assembly on silicon submount for self aligned fiber to waveguide coupling

Flip chip bonding by use of solder bumps has been widely developed to hybridize active devices such as lasers, detectors, and amplifiers, onto silicon microbenches. We report here a new method allowing hybridization of any kind of substrate onto a silicon submount with a passive and high precision self alignment process, the substrate being held in three dimensions, allowing coupling of waveguides to multiple fibers. Moreover the system allows a detachable configuration and avoids any additional micromachining of the waveguide substrate. Alignment of the waveguide axis with the V-grooves axis was obtained with an accuracy better than 2 /spl mu/m. Preliminary results indicate that the excess loss during the self-alignment and coupling of a fiber by insertion in a V-groove compared to an active alignment was typically of -3 dB.

Generation of second harmonic in a tunable/Q-switch Nd3+-doped fiber laser

In this paper, we report second harmonic generation in a tunable/Q-switch Nd3+-doped fiber laser using a LiNbO3-integrated optics device. The component is a low-voltage asymmetric Mach-Zehnder Interferometer. Laser emission occurs simultaneously at two wavelengths (lambda) 0 equals 1088 nm et (lambda) 2 equals 544 nm. As a driving voltage is applied to the LiNbO3 component, the lasing wavelengths are tuned by mode hopping. We demonstrate a Q-switch mode operating of that laser.

Modified coherence-modulation techniques for secure transmission

In this presentation, we discuss the security aspect of coherence modulation for telecommunications. Recently, we demonstrated a simple technique for decoding the signal without any decoder interferometer. We now demonstrate a secure alternative method based on the corruption of the interferometers optical path difference. Experimental results at low bit rate using fiber interferometers as well as transmission at high bit rates using large-imbalanced integrated optic interferometers are presented. Considerations about the polarization state of the light are also discussed.