Yannick Deshayes

Silver clusters embedded in glass as a perennial high capacity optical recording medium.

[∗] Dr. A. Royon , Dr. M. Bellec , G. Papon , Dr. B. Bousquet , Prof. L. Canioni Centre de Physique Moleculaire Optique et Hertzienne University of Bordeaux 351 Cours de la Liberation, 33405 Talence (France) E-mail: l.canioni@cpmoh.u-bordeaux1.fr K. Bourhis , Dr. T. Cardinal Institut de Chimie de la Matiere Condensee de Bordeaux University of Bordeaux 87 Avenue du Docteur Schweitzer, 33608 Pessac (France) Dr. Y. Deshayes Laboratoire de l ′ Integration du Materiau au Systeme University of Bordeaux 351 Cours de la Liberation, 33405 Talence (France)

Effects of silicone coating degradation on GaN MQW LEDs performances using physical and chemical analyses

This work presents a physics of failure (POF) methodology coupling failure signatures with physico-chemical analyses. The aim is to work out electro-optical failure signatures located in packaged InGaN/GaN Multiple Quantum Wells Light Emitting Diodes (MQW LEDs). Electrical and optical characteristics performed after accelerated ageing tests (30 mA/85 °C/1500 h), confirm a 65% drop of optical power and an increase of one decade of leakage current spreading at the silicone oil/chip interfaces. Through measurements of silicone coating fluorescence emission spectra, we demonstrate that the polymer enlarges the LED emission spectrum and shifts central wavelength. This shift is related to silicone oil spectral instability and the central wavelength of packaged LED appears to be temperature insensitive. In this paper, we discriminate the degradation of bulk silicone oil responsible for optical losses from the polymer/chip interface inducing larger leakage current.

Three-dimensional FEM simulations of thermomechanical stresses in 1.55 μm Laser modules

Abstract The purpose of this study is to present three-dimensional simulations using finite element method (FEM) of thermomechanical stresses and strains in 1550 nm Laser modules induced by Nd:YAG crystal Laser welds and thermal cycles on two main sub-assemblies: Laser submount and pigtail. Non-linear FEM computations, taking into account of experimental σ(e) measured curves, show that Laser welding process can induce high level of strains in columns of the Laser platform, bearing the Laser diode, responsible of an optical axis shift and a gradual drop of the optical power in relation with relaxation of accumulated stresses in the sub-assembly. In the case of thermal cycles, stresses can occur on elements sensitive to coefficient of thermal expansion mismatches such as solder joint between the Laser platform and thermoelectric cooler and as fiber glued into the pigtail leading to crack propagation with sudden drop of optical power. The main objective of the paper is to evaluate thermomechanical sensitivity and critical zones of the Laser module in order to improve mechanical stability after Laser weld and reach qualification standards requirements without failures. Experimental analyses were also conducted to correlate simulation results and monitor the output optical power of Laser modules after 500 thermal cycles (−40 °C/+85 °C VRT).

Proton effects on low noise and high responsivity silicon-based photodiodes for space environment

A series of proton irradiations has been carried out on p-n silicon photodiodes for the purpose of assessing the suitability of these devices for the European Galileo space mission. The irradiations were performed at energies of 60, 100, and 150 MeV with proton fluences ranging from 1.7×1010 to 1×1011 protons/cm2. Dark current, spectral responsivity, and dark current noise were measured before and after each irradiation step. We observed an increase in both dark current, dark current noise, and noise equivalent power and a drop of the spectral responsivity with increasing displacement damage dose. An analytical model has been developed to investigate proton damage effects through the modeling of the electro-optical characteristics of the photodiode. Experimental degradations were successfully explained taking into account the degradation of the minority carrier diffusion length in the N-region of the photodiode. The degradation model was then applied to assess the end-of-life performance of these devices ...

High-power diode laser bars and shear strain

The emitters at the edges of high-power laser bars tend to produce less power than emitters that are near the center of the bar. We suggest that shear strain, which owes to strain induced by bonding, creates through a photoelastic effect a weak birefringence that rotates the plane of polarization of the light. A rotation of the plane of polarization reduces the net gain for the lasing modes and hence leads to a lower output power for the emitters at the edges of the bars, where the shear strain is dominant.

Simulations of Thermomechanical Stresses and Optical Misalignment in 1550-nm Transmitter Optoelectronic Modules Using FEM and Process Dispersions

Expertise of packaging for optoelectronic components requires the solution of optical, mechanical, and electrical problems in the same way. The purpose of this paper is to present three-dimensional simulations using finite-element method (FEM) of thermomechanical stresses and strains in 1550-nm laser modules induced by Nd:YAG crystal laser welds and thermal cycles on main subassembly laser submount. Nonlinear FEM computations, taking into account of experimental sigma(epsiv) measured curves, show that the laser welding process can induce high level of strains in columns of the laser platform, bearing the laser diode, responsible of an optical axis shift and a gradual drop of the optical power in relation with relaxation of accumulated stresses in the subassembly (W. M. Sherry et al., ldquoHigh performance optoelectronic packaging for 2.5 and 10 Gb/s laser modules,rdquo in Proc. Electron. Compon. Technol. Conf., 1996, pp. 620-627). Typical stresses are close to 160 MPa with drift about 5 MPa with the dispersion of energy level of the laser Nd: YAG beam. The introduction of both material and process dispersion in order to evaluate their impact on product lifetime distribution has been taking into account. In the case of thermal cycles, stresses can occur on elements sensitive to coefficient of thermal expansion mismatches such as solder joints between the laser platform and thermoelectric cooler and as fiber glued into the pigtail leading to crack propagation with sudden drop of optical power. A previous paper demonstrated that laser submount is the most sensitive part of optical system (Deshayes, et al., ldquoThree-dimensional FEM simulations of thermal mechanical stresses in 1.55 mum laser modules,rdquo Microelectron. Rel., vol. 43, no. 7, pp. 1125 -1136, Jul. 2003). Experimental analyses were also conducted to correlate simulation results and monitor the output optical power of laser modules after 500 thermal cycles ( -40degC/ + 85degC VRT).

Correlation between forward-reverse low-frequency noise and atypical I–V signatures in 980 nm high-power laser diodes

Highlights • We observe atypical laser diode (LD) signatures in reverse I-V measurement identified as microplasma discharges. • Correlation between reverse I-V signatures and LFN measurements appears as a complementary tool for improvement of screening methodology for LD. • Reverse and forward noise spectra especially exhibit 1/f noise. • Some lasers reveal g-r noise component in bias voltages corresponding to reverse I-V slope changes and around ITH. • Presence of g-r noise leads to believe that point defect can be localized near the active zone.

Durability study of a fluorescent optical memory in glass studied by luminescence spectroscopy

Thermal stress at 100 °C for more than 3168 h of a fluorescent optical memory composed of laser written silver nano clusters embedded in glass has been performed. Measurements of luminescence spectra have been carried out at different times, showing a decreasing and an increasing evolution of the red and the blue part of the spectrum, respectively. This evolution has been attributed to the diffusion and the reorganization of different silver species inside the matrix, altering the internal electric field. Stark effect based modeling enables the degradation mode of the memory.

Failure Mechanisms in Packaged Light-Emitting Diodes Under Gamma Radiations: Piezoelectric Model Based on Stark Effect

Degradation of packaged light-emitting diodes (LEDs) under gamma irradiations has been investigated using usual electro-optical characterizations. Failure mechanisms have been revealed by an accurate degradation model taking into account the Stark effect in electroluminescence spectrum and piezoelectric field in the active zone. Gamma irradiations have induced an additional mechanical stress close to 0.25 MPa in the active layer resulting from the change of the polymer mechanical properties used on the LED package.

Stark Effects Model Used to Highlight Selective Activation of Failure Mechanisms in MQW InGaN/GaN Light-Emitting Diodes

This paper demonstrates the feasibility of creating specific defects in double-heterostructure InGaN/GaN commercial light-emitting diodes by neutron irradiation. Using controlled neutron energy, only one failure mechanism can be activated. Defects are located on the side of the chip and increase the leakage current driven by the well-known Poole-Frenkel effect with E c - E T = 130 meV electron trap energy level. The maximal amplitude of the optical spectrum also reveals a drop of about 20% associated with the rise of the leakage current. The Stark effect model highlights the origin of the degradation.