Frank Roeske

Preliminary Radiation Hardness Testing Of LiNbO 3 :Ti Optical Directional Coupler Modulators Operating At 810 Nm

Integrated optics have the potential to replace conventional electronics in many instrumentation applications; in many cases the integrated-optics approach is the only one that will achieve the necessary bandwidth and information-density goals. Thus far, has been done to address the prompt hardness of these devices to intense ionizing-radiation fields. We present preliminary data on the response of optical directional coupler modulators (ODCMs) to radiation from a Febetron. The Febetron produces energetic electrons in the 300-700 keV range in tilde 3-ns FWHM pulses, with a maximum dose rate of tilde 1014 rad/s. The operation of the ODCM is monitored during and promptly after the Febetron pulse impinges the device. Long-term effets are also monitored. These data are analyzed with respect to the operation of such devipes in a harsh inonizing-radiation environment.

Analog High-Bandwidth Single-Shot Data Link Using Integrated Optical Modulators And A High Fidelity Optical Streak Camera

We present preliminary data on the fidelity of an analog optical data link operating at 830 nm. This data link encodes an electrical signal on an optical carrier by the action of a commercially available integrated-optic modulator, a 2x2 switch, from Crystal Technology, Inc.(CTI) An optical streak camera is used to record the modulated optical carrier. With this single-shot system a precision of 2-5% is realized. The dynamic range of the system is approximately 30 dB (power). The present system bandwidth is limited to 3 Ghz by the CTI modulator. New modulator designs using travelling wave structures will soon extend the system bandwidth to around 10 Ghz. We discuss the potential for development of a high-fidelity multichannel analog link based upon this technology and the potential impact on instrumentation for the measurement of ultra-fast single-transient phenomena.

LiBbO3:Ti Directional-Coupler Modulators For High-Bandwidth, Single-Shot Instrumentation Systems Operating At 800 Nm

We update our work on optical directional-coupler modulators (ODCMs) for single-shot, analog instrumentation systems operating at 800 nm. We can now fabricate directional-coupler devices that have one input and two output pigtails, with insertion losses of 8.9 dB on average. Data for the ODCMs indicate an impulse response of less than 40 ps. We have implemented these devices in an ultrafast, x-ray measurement system. We discuss our data from this implementation and their implications for continued ODCM development.

Gallium Arsenide Integrated Optical Devices For High-Speed Diagnostic Systems

We discuss the design, fabrication, and evaluation of waveguide electro-optic modulators in gallium arsenide for application to high-speed diagnostic systems. We focus specifically on high bandwidth, single event analog modulation, and radiation susceptibility of these devices.

Overview of photonics research at Lawrence Livermore National Laboratory

We will describe research being conducted in the following areas: high-speed, 50 ohm, phased-matched modulators and their applications to digital links; promising new research on flat-panel displays that will be full color, fast response, very thin, and have a very high resolution; all optical switches that are extremely fast, integrable and do not have the latency problems that exist with current optical switches; semiconductor optical amplifiers that are monolithically integrable, more flexible and less expensive than existing fiber amplifiers; novel, semiconductor waveguide devices; and automated packaging techniques that will lower the cost of photonics components.

4-GHz analog data acquisition system using high-frequency guided-wave modulators

High-frequency modulators have been used to record very fast analog voltage pulses in the Nuclear Test Program at LLNL. A system consisting of 810 nm laser diode carrier sources, 7 GHz H-branched, balanced bridge modulators (YBBM), a kilometer of single-mode optical fiber and a streak camera recorder has been successfully fielded. The total system -3 db bandwidth is 4 GHz with a slow roll-off allowing the recoverable data capabilities of the system to approach 10 GHz. This system has provided us with a diagnostic tool that allows us to resolve high-frequency structure in our signals which has been calculated but never measured because of limitations in the resolution of previous measuring systems. A description of the system will be given with particular emphasis given to the YBBM modulator characteristics and performance. Fast pulse data recorded by the system will be shown and an indication of the accuracy with which the pulse can be reproduced will be provided. We expect this system to be a valuable tool that will be used regularly to study the physics of materials at extremely high temperatures and densities. Plans for upgrading the system to have a -3 db bandwidth of 7 - 8 GHz will also be discussed.

Radiation Effects On Gallium Arsenide Integrated Optical Devices

We discuss gallium arsenide integrated optical devices for high speed diagnostic systems. Specifically, we focus on the effect of radiation exposure on the performance characteristics of these devices.