Lasers

Contrary to popular belief, lasers are not used primarily as torture devices for secret agents who infiltrate evil complexes.  Lasers are one of the most versatile tools in the realm of electronics.  They are essential for a number of photonics applications like fiber optics.  They're also useful as an analysis technique for a wide variety of materials.

The problem with lasers is that they're not that efficient.  Yes, there are some really bright lasers out there, but they happen to draw a lot of power and generate quite a bit of heat.  To complicate matters further, most of our lasers are based on some compound III-V semiconductor mixes like GaAs or InP.  While these are great materials for creating a broad spectrum of frequencies, they are not compatible with a silicon process due to lattice mismatch.

All lasers require quantum confinement in at least one direction.  The modern laser is based on a quantum well that confines electrons into a 2-D plane.  While quantum wells are relatively easy to manufacture, they are not very efficient in terms of quantum efficiency.  Hence, the input-output ratio isn't that high.

New structures in nanotechnology have opened the door for brighter and more efficient lasers.  To start things off, a nanowire offers confinement in two directions.  Large nanowire arrays have already been used to emit coherent light at ultraviolet (and many other) frequencies.  The problem with nanowire lasers is that often they require another laser of a different frequency to 'pump' it with electrons.  From a device standpoint this is not desirable, as we want lasers to work independent of other lasers.

The most exciting development of late has been the quantum dot laser.  The q-dot offers the maximum confinement for the best efficiency.  A number of innovative approaches have also provided new power sources for electron pumping.  The best example of this is a quantum dot laser that is a matrix of quantum dots and an electrically active polymer matrix.  Depending on the laser type, the polymer can either remove or donate electrons from the quantum dots.  This is a critical step for laser operation.

Since lasers are now used in daily life for a variety of optical media, their fabrication in the nanometer scale will ultimately pave the way for a new class of devices and storage media.  A large portion of work has already been completed, but an affordable nanoscale laser is still in development.