6:00pm: Networking/pizza social
7:00pm: Presentation
8:00pm: Adjourn

Cost: Free

Title

Molecularly Engineered Semiconductor Cluster Nanocomposites for Advanced Photonics

Speaker

Dr. Ron Kubacki, Ionic Systems

Abstract

From a systems level it is impossible to differentiate efficiency in the electrical domain from the optical domain if photonics are incorporated. Planar waveguide devices and active components, such as modulators, that require high operating powers, waveguide structures that dissipate more optical energy than they transport, and materials/processes that are incapable of presenting an efficient path to higher levels of integration present significant challenges. Molecular engineering enables materials with lower propagation losses and higher performance/more energy efficient active photonic devices to be fabricated. Dr. Kubacki previously reported on work using plasma enhanced chemical vapor deposition (PECVD) for active and passive photonics. This presentation will update work in two key areas: 1) material and process development for ultra low loss photonic waveguides and 2) results in material development for active device fabrication, particularly large χ² effects. Results presented in both areas are believed to represent the current state of the art for loss and electro optic activity produced by any material.

The approach is a self assembled silicon quantum cluster (SQC) nanocomposite which possesses unique applicability to the construction of microphotonic circuits. Through exposure to deep ultraviolet radiation, large changes in as deposited index of refraction can be induced (i.e. > 1.0). The high contrast possible with the process permits core and cladding index contrast optimization. Reduction of losses in the SQC material focused on investigation of precursors and binding matrix formation. Non linear optical properties were researched by altering the size and density of semiconductor clusters and stroichiometry changes to the binding matrix. Upon exposure to deep ultraviolet radiation in the presence of oxygen, as supplied by air for example, surface states of semiconductor quantum clusters are altered producing a reduction in index of refraction. The large index contrast a permits local trimming of index of refraction to optimize photonic structure fabrication. No other material set has demonstrated the index contrast range of the SQC nanocomposite. Losses measured here were studied relative to index contrast between core and cladding. The process investigated further examined host matrix formation using a lower loss halogenated material. Ron will update work that has produced on chip waveguides with losses of 0.445 dB/m and their use in integrated photonic devices.

Small semiconductor clusters of silicon have been the subject of a number of theoretical and experimental studies. Several of the smaller silicon clusters are calculated to be polar, with dipole moments of several tenths to several Debye. Si3 exhibits suitable weak polar nature to explore optical nonlinearities, and was self assembled into the binding matrix in the PECVD reactor. No cluster alignment was used during deposition for results presented here although it is available to increase the effect. SQC alignment impact on r33 was studied by applying a DC bias during r33 measurement. Initial r33 measurements were 342.16 pm/V. Dr. Kubacki will report on the current development which has produced r33 of 1285.73 pm/V. Ron will briefly discuss applications, primarily for the military /aerospace customer, that combine both the ultra low loss waveguide with the active NLO material. Theoretical calculations predict that larger clusters, up to Si19, can have an order of magnitude greater response than Si3 and are currently under investigation. The computed polarizabilities per atom tend to decrease with increasing cluster size beyond approximately twenty atom cluster size and represents the upper theoretical limit at this time.

Biography

After receiving his doctorate in Physics from the University of Surrey in 1976, Dr. Kubacki held positions at Bell & Howell, NASA, Armorlite, and Tencor before founding Ionic Systems in 1979. He has worked in semiconductor processing equipment development and thin film research including PECVD apparatus and materials development for nearly 30 years. He has guided research programs in materials and device development undertaken by Ionic Systems for commercial and government customers including Northrop Grumman, Raytheon, Hughes Radar Systems Group, Lockheed Missiles and Space, Missile Defense Agency, Defense Threat Reduction Agency, DARPA, US Air Force, US Navy, U.S. Army, SPAWARS, and Department of Energy. His current focus is on the use of PECVD to molecularly engineer materials and develop manufacturing processes to enable innovative devices for photonics, microelectronics, and their monolithic integration. He has published over 25 technical papers, holds over ten sole inventor patents and received multiple certificates of recognition from NASA while a Visiting Executive from Industry employed by Bell and Howell. He is a member of IEEE, SPIE, OSA, and MRS. He chaired the Integrated Optoelectronics Session at the 2006 Annual IEEE LEOS meeting, Montreal, CN.