Stress Photonics (United States)

Optical Power Delivery (OPD), also known as Power By Light (PBL), shows great potential as a solution for energy transfer in situations where traditional methods are impractical or infeasible. This includes delivering electrical energy wirelessly or through fiber over long distances, or in scenarios requiring electromagnetic isolation. Optical Wireless Power Transfer (OWPT) delivers power to distant autonomous sensors and ensures efficient electrical and electromagnetic isolation. This technology is applicable in space exploration for beaming power to satellites or solar generated power from satellite to ground. In industrial settings, it provides power access in remote or hard-to-reach locations and facilitates the charging of robots and other autonomous devices. Additionally, it can be used for underwater energy transmission. This talk will explore the transformative applications of this emerging technology, as well as the various technological, safety, and economic challenges that need to be addressed for it to achieve commercial success.

Red laser diodes were fabricated on GaAs and GaAsP metamorphic-superlattice-substrates. The tensile strained QW on GaAs emitted 45% PCE, 638nm, TM-polarized light at 880mW CW. The compressively strained QW on the metamorphic structure emitted 639nm TE-polarized light with Tq=90K and Tj=300K.

The infrared grey-field polariscope (IR-GFP) has been developed to provide rapid, full-field stress analysis for infrared-transparent materials. Grey-field photoelastic theory is outlined and the advantages of this implementation for microelectronic materials inspection highlighted. The capabilities of this scientific tool are proven using standard sample geometries fabricated from single crystal silicon substrates and the general applicability of the instrument demonstrated on bonded devices and silicon wafer geometries. Stress resolution in silicon wafers is better than 0.1MPa at wafer inspection speeds of 10s for a 100mm wafer. Initial applications of the IR-GFP have shown that the tool provides improvements in defect detection and stress quantification when compared to conventional infrared transmission imaging while also providing several important advantages over other currently utilized inspection technologies.

Thermal methods have been recognized above other NDI methods for rapid inspection of large structures. Thermal methods are safe, convenient and relatively inexpensive. Coating tolerant thermography is specifically designed to meet the demands of more challenging field conditions.The technique's ability to differentiate between chipped paint and structural flaws is essential to field performance. However, equally important is the packaging of the system. The system must be lightweight, safe and inexpensive to maintain. This technique utilizes thousands of watts of radiant energy emanating from a hand held system. Inefficiencies in the projection optics can result in heating of the system itself, which then would necessitate significant cooling. This paper describes a unique projection system that can efficiently convert the energy emitted by an inexpensive incandescent line source into several projected stirpes for coating tolerant thermography.

A new thermographic technique, Forced-Diffusion Thermography (FDT), is described. Forced-Diffusion Thermography uses a continuously projected dynamic heat pattern to set up appropriate combinations of lateral and through-depth heat flow in structures. A synchronous imaging IR camera is used to measure the structures thermal response to a patterned heat flux in order to find flaws such as cracks and delaminations. A numerical model of the technique is used to describe the thermal responses to cracks and delaminations. Experimental data is presented for the case of a fatigue crack in a 2 mm thick aluminum skin.