High-Rate Deposition Of Rare-Earth Doped Silicate Nanoparticles For Porous & Dense Optical Films
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High-Rate Deposition Of Rare-Earth Doped Silicate Nanoparticles For Porous & Dense Optical Films Craig R. Horne1,2, Pierre de Mascarel2, Russell Blume2, Jesse Jur2, Cecile Cohen-Jonathan2, Michael Chapin2, Jonathan Posner2, Wei Cho Foo2, Christian Honeker2, Qing Zhu2, Shiv Chiruvolu1,2, Ronald Mosso1,2, and William McGovern1,2 1. NanoGram Corporation, 2911 Zanker Rd., San Jose, CA 95134 2. NeoPhotonics Corporation, 2911 Zanker Rd., San Jose, CA 95134 ABSTRACT A novel deposition process has been developed for manufacturing of high quality rare-earth doped glass films with complex composition. This process, Laser Reactive Deposition (LRD™), comprises photothermal laser pyrolysis using an aerosol feedstock coupled with deposition of the resulting nanoparticle product onto Si substrates with our without an underlying glass film. This paper describes this novel process as well as the structure, properties and performance of the Erdoped, multicomponent silicate glass films produced to date with this process. INTRODUCTION Integrated planar lightwave circuits (PLCs) are required for low-cost telecommunication components. Integration requires advanced circuit and device designs that are enabled by the multi-functional properties of complex materials. An example of desired complex materials are alkali, alkaline earth, and rare-earth (RE) containing glasses for amplification [1,2]. Amplification within integrated PLCs is necessary to overcome insertion and propagation losses inevitable within multifunctional devices. Therefore, realization of integrated PLCs requires the ability to develop and manufacture high quality RE doped films. Laser Reactive Deposition™ (LRD) is based on laser pyrolysis (LP), a method in which a feedstock stream containing precursors of the desired product and an absorbing species or sensitizer is introduced into a reaction chamber whereupon it intersects a laser beam. A photothermal laser-reaction zone (LRZ) is initiated through the coupling of the laser beam and absorbing species along with subsequent energy transfer to the precursor species in the feedstock plume. The combination of feedstock stream velocity and planar beam cross section create LRZ residence times on the order of microseconds. Consequently, the LRZ is a well-defined region of high temperature where homogenous nucleation of particles takes place but growth is mediated by thermal gradients on the order of 103 to 105 oC/cm. An elongated precursor delivery nozzle extends the LRZ parallel to the axis of the laser beam, creating a curtain of nanoparticles entrained by the flow of process gases through the reactor. Nanoparticles comprising elements from every chemical group of the periodic table and complex stoichiometry (e.g. quintary compounds) have been successfully synthesized by NanoGram’s commercial LP process, Nano Particle Manufacturing (NPM™), for a variety of applications, including batteries, electronics and optics [3,4]. The LRD™ process combines LP with a deposition mechanism in which the nanoparticles impinge upon and
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