[Show abstract][Hide abstract] ABSTRACT: High power diode laser arrays offer a variety of applications in pumping of solid state laser systems
for industry, scientific research, entertainment display and medical treatment etc, due to their higher electrical-optical conversion efficiency, compact size and long lifetime. Currently, most of commercial high power semiconductor laser array/bar products use single quantum well (SQW) construction in the active region. In order to achieve higher optical power at lower driving current without altering the radiation characteristics of the laser diodes, a new laser chip constructed by double quantum well (DQW) active region has been developed. For the DQW laser, two layers of individual emitters are stacked on top of each other. The two layers of emitters in a DQW are in serial connection. Hence, compared with the conventional SQW laser, a doubled output power from DQW under the same drive current could be obtained. However, the transient/peak thermal density generated from these lasers is very high, especially for the up layer in the active region of DQW laser. Therefore, the DQW can more suitably operate in quasi-continuous wave (QCW) mode. It is a challenge to dissipate the heat generated from the up layer of DQW laser. In this work, a double-side cooling technology was developed and the packaging of high power density DQW semiconductor laser array using that technology was presented. Finite element numerical analysis based simulations to analyze the transient thermal behavior of a water-cooled-packaged semiconductor lase
r array operating at QCW mode was also presented in this paper. Based on the numerical simulation and analysis, a series of DQW semiconductor lasers with high performances were fabricated. The performances of laser diode arrays operating at QCW mode, including the characteristics of Power-Current-Voltage (LIV), spectrum, near-field, and lifetime were characterized.
[Show abstract][Hide abstract] ABSTRACT: High power semiconductor laser arrays have been widely used in many fields, such as pumping solid state laser aerospace, industry, medicine and display. For many applications, high power semiconductor lasers operating quasi-continuous wave (QCW) mode are demanded. For QCW laser, the output peak power is higher and average power is low. Therefore, the transient thermal density is very high. The most common method of removing the large amounts of waste heat in a semiconductor laser package is by using commercially-available copper micro-channel coolers (MCC). However, due to the coefficient of thermal expansion (CTE) mismatching between copper and laser chip, hard-solder cannot be directly used. On the other hand, indium solder has the problem of electro-thermal migration when the temperature grads were high in QCW mode. Furthermore, copper material is susceptible to erosion and corrosion. To overcome these hurdles in many applications, a novel macro channel cooler (MaCC) was presented in this work. The thermal behavior of MaCC-packaged high power semiconductor laser arrays in QCW mode was studied using finite element analysis (FEA). A high power of >250W QCW semiconductor laser array/bar using hard solder was fabricated. The performances of laser arrays, including output power, slope efficiency, threshold, conversion efficiency, spectral width, near field, lifetime etc. were characterized. The measured results indicated that the output power of a MaCC- packaged high power semiconductor laser array was very close to that of copper micro-channel cooler. Based on MaCC-packaged single laser array/bar, multiple-bar stack and two dimension area array lasers with output powers of several kilowatts and several tens of kilowatts were fabricated.