This paper reviews recent progress of high-power 14xx-nm pump lasers using AlGaInAs/InP material. This material has superior temperature characteristics to conventional InGaAsP/InP. As a result, it is more suitable for high current and high efficiency operations as well as uncooled applications for the high power 14xx-nm lasers, which are required for advanced optical amplifications. The laser module consists of a laser chip coupled to a fiber lens and mounted on a thermoelectric cooler in a standard butterfly package. The wavelength of the laser can be stabilized with an external fiber Bragg grating (FBG). We have demonstrated a maximum module fiber output power of 550mW at 1.75A and characteristic temperatures of T<sub>0</sub> = 99K and T<sub>1</sub> = 348K over a range of chip heat-sink temperatures from 15°C to 50°C. To the best of our knowledge, these are the highest efficiency and temperature characteristics from a single-mode 14xx-nm semiconductor laser module capable of over 0.5W fiber output power. At a chip heat-sink temperature of 70°C, a power of 360mW was obtained for a laser module with FBG, which is the highest reported to date for any wavelengths from 1300nm to 1600nm and would enable uncooled applications of the 14xx-nm lasers in the future.
The dynamics of two mutually coupled semiconductor lasers is studied experimentally and numerically for weak coupling. The two lasers are pumped at different levels and have dissimilar free-running relaxation oscillation frequencies and intensities. We have found that the two lasers exhibit large amplitude intensity oscillations for one laser and small amplitude intensity oscillations for the other laser. In our previous work, we studied the effect of the coupling strength. In this paper, we keep the coupling strength fixed and examine the effect of the detuning between the optical frequencies. As the detuning comes close to a multiple of the relaxation oscillation frequency of one of the two lasers, we observe the amplification of the intensities due to resonance and synchronization. Our experimental observations of the laser spectra are in good agreement with the numerical spectra and bifurcation diagrams computed from the semiconductor laser rate equations.
The dynamics of two mutually coupled but non-identical semiconductor lasers are studied experimentally, numerically and analytically for weak coupling. The lasers have dissimilar relaxation oscillation frequencies and intensities, and their mutual coupling strength is asymmetric. We find that the lasers may entrain to the relaxation oscillation frequency of either one of the lasers. The form of entrainment is a special form of synchronization, called localized synchronization, where one laser exhibits strong oscillations and the other one weak oscillations. We perform a bifurcation analysis to explain the mechanism of entrainment by taking advantage of the inherently large parameters in a semiconductor laser, the linewidth enhancement factor (alpha) and the ratio of the carrier and photon lifetime T.