Yann Boucher

Spectral properties of amplified spontaneous emission in semiconductor optical amplifiers

We present a theoretical investigation of the spectral properties of spontaneous emission in semiconductor optical amplifiers. We use an extended (3/spl times/3) transfer matrix formalism to derive in the spectral domain an expression for the total longitudinally averaged internal field, which is valid regardless of the levels of optical input and bias current. The material parameters are saturated not only by the monochromatic signal, but also by the amplified spontaneous emission, filtered into the resonance modes of the structure, and integrated over its whole spectral range.

Additional modal selectivity induced by a localized defect in quarter-wave-shifted DFB lasers

The effects of a localized impurity upon the threshold spectral properties of quarter-wave-shifted distributed feedback (QWS-DFB) lasers are analyzed. The singularity, which can exhibit absorbing, dephasing, as well as reflecting properties, is mathematically described by a transfer matrix so that its inclusion in the usual matrix formalism of coupled-wave equations is easy. The exact location of the singularity, its strength, as well as the grating phase with respect to the origin are found to affect greatly the modal behavior of the structure. The localized defect interacts differently with each mode due to their intracavity stationary field pattern, so that a modally selective center is produced. A correct optimization of the singularity parameters thus enables an enhancement of the laser performance.

Radio frequency spectral characterization and model parameters extraction of high Q optical resonators

A microwave domain characterization approach is proposed to determine the properties of high quality factor optical resonators. This approach features a very high precision in frequency and aims to acquire a full knowledge of the complex transfer function (amplitude and phase) characterizing an optical resonator using a microwave vector network analyzer. It is able to discriminate between the different coupling regimes, from the under-coupling to the selective amplification, and it is used together with a model from which the main resonator parameters are extracted, i.e. coupling factor, intrinsic losses, phase slope, intrinsic and external quality factor.

Guided photoluminescence study of Nd-doped silicon rich silicon oxide and silicon rich silicon nitride waveguides

Planar waveguides made of Nd3+-doped silicon rich silicon oxide (SRSO) and silicon rich silicon nitride (SRSN) have been fabricated by reactive magnetron sputtering and characterized with special emphasis on the comparison of the guided photoluminescence (PL) properties of these two matrices. Guided fluorescence excited by top surface pumping at 488 nm on planar waveguides was measured as a function of the distance between the excitation area and the output of the waveguide, as well as a function of the pump power density. The PL intensity increased linearly with pump power without any saturation even at high power. The linear intensity increase of the Nd3+ guided PL under a non-resonant excitation (488 nm) confirms the efficient coupling between either Si-np and rare-earth ions for SRSO or radiative defects and rare earth ions for SRSN. The guided fluorescences at 945 and 1100 nm were observed until 4 mm and 8 mm of the output of the waveguide for Nd3+ doped SRSO and SRSN waveguides, respectively. The gu...

Quasi-periodic complex-coupled distributed-feedback structures with an exponential-like gradient of coupling

We investigate theoretically the linear properties of quasi-periodic complex-coupled distributed-feedback (DFB) structures in which the coupling constants experience a longitudinal variation along the propagation axis according to an exponential-like relationship (exp, sh, ch, /spl middot//spl middot//spl middot/). The results of the simulations are in good accordance with what could be expected at first sight from the particular form taken in this case by the coupled-wave equations. In particular, the gradient of coupling can provide a shift, either of the apparent average absorption (respectively, gain) or of the detuning from Bragg resonance, depending upon its exact form, Moreover, we show that this shift is asymmetric with respect to the direction of propagation, leading to a nonreciprocal behavior in reflection. We extend our analysis up to the laser modes at threshold.

Modal Analysis of Graded-Index Porous Silicon Slab Waveguides

We investigate the modal properties, for TE polarization, of graded-index porous silicon slab waveguides with linearly varying dielectric permittivity. Using transfer matrix formalism, we derive all-analytical expressions, in terms of special functions of the Bessel class, for the propagation constant and the transverse profile of each mode.

Wavelength and Bandwidth Tunable TPA Semiconductor Microcavity Detector for High-Speed Signal Processing in WDM Systems

We propose a novel design for a semiconductor microcavity nonlinear detector, based on two-photon absorption, for high-speed signal processing applications in future wavelength division multiplexing (WDM) systems. By inserting a phase section and a gain section in the resonant cavity, we could achieve wavelength and bandwidth tunability of the nonlinear detector. Theoretical investigation is carried out in the frame of an extended transfer matrix formalism, leading to the self-consistent calculation of the device properties. We model the design and characteristics of a GaAs/AlGaAs microcavity suitable for selective processing of different WDM channels, operating at various data rates and modulation formats.

SiO2-SnO2:Er3+ transparent glass-ceramics: fabrication and photonic assessment

This work focuses on the fabrication processes and photonic assessment of SiO2-SnO2:Er3+ monoliths. To obtain the crack-free and densified system, the sol-gel derived synthesis protocols and heat-treatment processes were optimized. The absorption measurements were employed to assess the effect of the heat-treatment on the samples and specially to estimate the –OH content. The XRD patterns were used to investigate the crystallization as well as the structure of the monoliths. The emission spectra, performed at different excitation wavelengths, evidence the presence of Er3+ in the SnO2 nanocrystals and the energy transfer from SnO2 to the rare earth ions. In addition, the efficient role of SnO2 nanocrystals as Er3+ sensitizers are also experimentally confirmed in this system.

Fabrication by rf-sputtering and assessment of dielectric Er3+ doped monolithic 1-D microcavity for coherent emission at 1.5 um

All Er3+ doped dielectric 1-D microcavity are fabricated by RF sputtering technique. The microcavity is composed of half wave Er3+ doped SiO2 active layer inserted, between two Bragg reflectors consisting of seven pairs of SiO2/TiO2 layers also doped with Er3+ ions. The morphology of the structure is inspected with scanning electron microscopy. Transmission measurements show the third and first order cavity resonance at 530 nm and 1535 nm, respectively. The photoluminescence measurements were obtained by optically exciting at the third order cavity resonance using 514.5 nm Ar+ laser with an excitation angle of 30°. The Full Width at Half Maximum of the emission peak at 1535 nm decrease with the pump power until the spectral resolution of the detection system of 2.3 nm. Moreover, the emission intensity presents a non-linear behavior with the pump power and a threshold at about 4 μW.

Optical resonators metrology using an RF-spectrum approach

A Microwave domain characterization technique is proposed to measure the optical properties of high quality factor optical resonators, featuring a very high precision in frequency which can be as good as 1 Hz. It aims to acquire a full knowledge of the complex transfer function (amplitude and phase) characterizing these resonators. It is shown that the amplitude response gives access to the measure of several parameters like the free spectral range and the quality factor. Moreover the phase transition at the resonance is used to define the coupling regime and to calculate the resonator parameters: transmission coefficient and intra-cavity losses.