A novel, 9XX nm fiber-coupled module using arrays of highly reliable laser diode bars has been developed. The module is capable of multi-kW output power in a beam parameter product of 80 mm-mrad. The module incorporates a hard-soldered, isolated stack package compatible with tap-water cooling. Using extensive, accelerated multi-cell life-testing, with more than ten million device hours of test, we have demonstrated a MTTF for emitters of >500,000 hrs. In addition we have qualified the module in hard-pulse on-off cycling and stringent environmental tests. Finally we have demonstrated promising results for a next generation 9xx nm chip design currently in applications and qualification testing
The scalability of semiconductor diode lasers to multi-kilowatt power levels has increasing importance in direct diode material processing applications. These applications require hard-pulse on-off cycling capability and high brightness achieved using low fill-factor (FF) bars with a tight vertical pitch. Coherent uses 20%FF bars operated at <60W/bar packaged on water-cooled packages with a 1.65mm vertical pitch in the Highlight D-series, which achieves <8kW of power in a < 1mm x 8mm beam line at a working distance of ~ 280mm. We compare thermal measurement results to thermal fluid flow simulations to show the emitters are cooled to low junction temperatures with minimal thermal crosstalk, similar to single emitter packaging. Good thermal performance allows for scaling to operation at higher power and brightness. We present accelerated life-testing results in both CW and hard-pulse on-off cycling conditions.
Our goal is to develop a rectifying antenna (rectenna) applicable to solar spectrum energy harvesting. In particular, we
aim to demonstrate viable techniques for converting portion of the solar spectrum not efficiently converted to electric
power by current photovoltaic approaches. Novel design guidelines are suggested for rectifying antenna coupled
tunneling diodes. We propose a new geometric field enhancement scheme in antenna coupled tunneling diodes that uses
surface plasmon resonances. For this purpose, we have successfully implemented a planar tunneling diode with
polysilion/SiO2/polysilcon structure. An antenna coupled asymmetric tunneling diode is developed with a pointed
triangle electrode for geometric field enhancement. The geometrically asymmetric tunneling diode shows a unique
asymmetric tunneling current versus voltage characteristic. Through comparison with crossover tunneling diodes, we
verified that the current asymmetry is not from the work function difference between the two electrodes. Results of RF
rectification tests using the asymmetric diode demonstrate that our approach is practical for energy harvesting
application. Furthermore, we describe how surface plasmons can enhance the electric field across the tunnel junction,
lowering the effective "turn-on" voltage of the diode, further improving rectification efficiency.
The need for efficient detection of biochemical agents is becoming more compelling. High sensitivity chemical and biological sensors, based on etched core fiber Bragg gratings that detect change in the index of refraction of surrounding solutions, were developed to measure the index of refraction of different solutions. A sensitivity of 1394 nm/riu was achieved for a core diameter of 3.4 μm. Assuming an experimental wavelength resolution of 0.01 nm, we were able to detect an index change of 7.2⋅10-6. These chemical sensors, properly sensitized using common glutaraldehyde chemistry, can be effectively used as biosensors. A 20 base single stranded DNA of concentration of 0.7 μg/ml was successfully detected. Some ideas are also proposed for sensitivity improvement of the sensor, like using the higher order modes. It is shown that the higher order modes can also provide information about the cause of the fundamental shift, whether it is due to refractive index change or due to external effects like temperature and stress.