Fiber combining multiple pump sources for fiber lasers has enabled the thermal and
reliability advantages of distributed architectures. Recently, mini-bar based modules have been
demonstrated which combine the advantages of independent emitter failures previously shown in
single-stripe pumps with improved brightness retention yielding over 2 MW/cm<sup>2</sup>Sr in compact
economic modules. In this work multiple fiber-coupled mini-bars are fiber combined to yield an
output of over 400 W with a brightness exceeding 1 MW/cm<sup>2</sup>Sr in an economic, low loss
As GaAs based laser diode reliability improves, the optimum architecture for diode pumped
configurations is continually re-examined. For such assessments, e.g. bars vs. single emitters, it is
important to have a metric for module reliability which enables comparisons that are the most
relevant to the ultimate system reliability. We introduce the concept of mean time between emitter
failures (MTBEF) as a method for characterizing and specifying the reliability of multi-emitter
pumps for ensemble applications. Appropriate conditions for an MTBEF model, and the impact of
incremental changes of certain conditions on the robustness of the model are described.
In the limit of independent random failures of individual emitters as the dominant failure mechanism
it is shown that an ensemble of multi-emitter modules can be modeled to behave like an ensemble of
single emitter modules. The impact of thermal acceleration due to failed emitters warming other
emitters on a shared heat-sink is considered. Data taken from SP built multi-emitter devices bonded
with AuSn on CTE matched heat-sinks is compared with the MTBEF model with and without
correction for the thermal acceleration effect.
Cavity ring-down spectroscopy (CRDS) can provide high sensitivity, high precision, and absolute calibration in a wide range of environments. We report on a compact cavity ring-down spectrometer that can measure atmospheric toxic industrial compounds such as hydrides and hydrazines. The ring-down spectrometer is fully contained in two 5 ¼" tall, 19" wide rack mount enclosures and utilizes a robust, near-infrared, fiber-coupled tunable diode laser. The instrument has a baseline sensitivity of 8 x 10<sup>-11</sup> cm<sup>-1</sup>/Hz<sup>½</sup>. We will present the results of this study, which demonstrates the capability to detect toxic gases such as arsine, silane, and hydrazine (simulated using ammonia) in air at parts per billion (ppb) concentrations in less than 1 minute. We will also present results on CRDS instrument performance, including zero drift, precision, absolute accuracy, and linearity over a wide range of environmental operating conditions.
In the past, the interferometric fiber optic gyro (IFOG) has generally been viewed as an angular rate sensor. This may appear true on a coarse time scale. However, a study of its behavior within the transit time of light through the fiber optic coil shows that, in reality, the IFOG is a rate integrating gyro with a very short memory. Making use of fast sampling and accumulation, the rate integrating characteristic can be retained. Mechanized that way Litton IFOG exhibits an output response which is similar to