Passive temperature compensation of a coolerless 1.55-μm diode laser mounted on a bimetallic heatsink

Stability of the threshold current and differential efficiency, in the presence of environmental temperature changes, are important in all-optical communication systems, and wavelength stability will become critical in dense WDM systems. Because thermoelectric coolers used to provide temperature control consume excessive power and are unreliable, coolerless lasers have been developed for low-cost systems. By using strained MQW active regions with wide band gap barriers, and effective facet coatings, the drop in efficiency with rising temperature has been eliminated, and the degradation of threshold current reduced, although there is still room for improvement, particularly at 1.55 μm. Very little work has been reported for wavelength stabilization. We have previously demonstrated that temperature-dependent hydrostatic stress, arising from differential thermal expansion, can be used to reduce wavelength drift. We demonstrate here that temperature-dependent uniaxial stress can be used to reduce degradation of the threshold current and efficiency, as well. We fabricated a stress-inducing heatsink from the low-expansion alloy Invar, with an insert made from aluminum