QCLs are becoming the most important sources of laser radiation in the midwave infrared (MWIR) and longwave
infrared (LWIR) regions because of their size, weight, power and reliability advantages over other laser sources in the
same spectral regions. The availability of multiwatt RT operation QCLs from 3.5 μm to >16 μm with wall plug
efficiency of 10% or higher is hastening the replacement of traditional sources such as OPOs and OPSELs in many
applications. QCLs can replace CO2 lasers in many low power applications.
Of the two leading groups in improvements in QCL performance, Pranalytica is the commercial organization that has
been supplying the highest performance QCLs to various customers for over four year. Using a new QCL design
concept, the non-resonant extraction , we have achieved CW/RT power of >4.7 W and WPE of >17% in the 4.4 μm -
5.0 μm region. In the LWIR region, we have recently demonstrated QCLs with CW/RT power exceeding 1 W with
WPE of nearly 10 % in the 7.0 μm-10.0 μm region. In general, the high power CW/RT operation requires use of TECs to
maintain QCLs at appropriate operating temperatures. However, TECs consume additional electrical power, which is
not desirable for handheld, battery-operated applications, where system power conversion efficiency is more important
than just the QCL chip level power conversion efficiency. In high duty cycle pulsed (quasi-CW) mode, the QCLs can be
operated without TECs and have produced nearly the same average power as that available in CW mode with TECs.
Multiwatt average powers are obtained even in ambient T>70°C, with true efficiency of electrical power-to-optical
power conversion being above 10%.
Because of the availability of QCLs with multiwatt power outputs and wavelength range covering a spectral region from
~3.5 μm to >16 μm, the QCLs have found instantaneous acceptance for insertion into multitude of defense and homeland
security applications, including laser sources for infrared countermeasures for protecting aircraft from MANPADS,
testing of infrared countermeasures, MWIR and LWIR lasers for identify-friend-or-foe (IFF) personnel beacons, infrared
target illuminators and designators and tunable QCL applications including in-situ and standoff detection of chemical
warfare agents (CWAs) and explosives. The last of these applications addresses a very important and timely need for
detection of improvised explosive devices (IEDs) in combat environments like Iraq and Afghanistan.