nullThe following is information on QCL lifetime assessment and testing.

The first level of testing is at the wafer level. When a new wafer is manufactured, several devices are tested at various levels  (bar-testing and mounted laser  characterization) before a laser is to be sold. This ensures that there are no generic  conditions that would affect all of the lasers that were produced.  

Additionally, each laser is then tested individually multiple times and the results of these tests are recorded on a datasheet that is unique to each laser. Each laser is re-tested prior to shipment. Thus, every shipped laser will have been tested more than once and on different days before you receive it to ensure quality.

Once in a while, some lasers are selected for long-time testing. Some have been tested for up to 32’000 hours of continuous operation at Alpes with no degradation of maximum performance. This external study has operated various types of QCLs for over 1.5 million device-hours and  has found that the mean time to failure of quantum cascade lasers operating at a heat-sink temperature of 25°C is expected to be 809’000 hours or 92 years of continuous operation. Furthermore, Alpes users have reported operating lasers in the field for extended periods of time.  A specific example can be found in this paper which describes an experiment that ran for 4 years uninterrupted with no degradation in performance.

In addition to the laser chip MTTF,  a typical laser package contains other parts that can degrade with time. In particular, the Peltier cooler will see its performance degrade with time and the coldest reachable temperature will slowly increase. Furthermore, the soldering of the chip to the submount may degrade which will affect the effective temperature of operation to reach a specific wavelength. These effects are slow and can be reversed by re-encapsulating the chip if the specifications are no longer reached within the warranty period. By design, packaged lasers should remain within their specifications for up to 5 years.