The first was a collaboration between Harvard and several European institutions including the Universities of Jena, Gottingen, and Bremen in Germany. The multi-national group engineered a mass-producible on-silicon LED made from zinc oxide nanowires. The LEDs could be see a multitude of uses, from high-density optical interconnects to on-chip chemical sensors.

The second, only a week later, was the development of a room-temperature terahertz frequency laser. This group, led by research associate Mikhail Belkin and professor Capasso, used a specially designed quantum-cascade laser (QCL) with dual emitters to produce a five terahertz beam via difference frequency generation. Though the laser can only operate at several hundred nanowatts at room temperature, commercial thermoelectric coolers would allow it to produce beams in the microwatt range. Terahertz frequency lasers can penetrate many substances and would be useful for medical imaging, inspecting the internal integrity of delicate structures, or detecting chemical and biological agents within sealed containers.

This week's electronic issue of Nature Photonics contains yet another invention by a team co-led by professor Capasso and features work by Harvard and scientists from Hamamatsu Photonics from Hamamatsu, Japan. Capasso and graduate student Nanfang Yu report their work in the form of a new highly directional semiconductor laser.

“Our innovation is applicable to edge-emitting as well as surface-emitting semiconductor lasers operating at any wavelength—all the way from visible to telecom ones and beyond,” explains Capasso in a HarvardScience news release. “It is an important first step towards beam engineering of lasers with unprecedented flexibility, tailored for specific applications. In the future, we envision being able to achieve total control of the spatial emission pattern of semiconductor lasers such as a fully collimated beam, small divergence beams in multiple directions, and beams that can be steered over a wide angle.”

Similar to the previously mentioned terahertz laser, the basic component of the new directional semiconductor laser is a mid-infrared QCL unit. To curb the tendency of commercial semiconductor lasers towards beam divergence, the researchers specially crafted a structure called a plasmonic collimator. The collimator, consisting of an aperture and a pattern of sub-wavelength grooves, is imprinted directly to the facet of the QCL and servers to narrow the beam output significantly.

Again, similar to the terahertz laser, the new directional semiconductor lasers could find application in biological and chemical detection. Their high power capacity and operating wavelength, coupled with the newly gained low-divergence output, would be more suitable for detecting such agents in the atmosphere, however, making them a useful tool for homeland security or environmental monitoring.

The technology could also greatly benefit the telecommunications sector. A highly directional beam output would greatly reduce or eliminate the need for expensive beam coupling lenses currently used in optical networks. Refined lasers could be more easily injected directly into the fiber optics and waveguides of these systems reducing system complexity and cost.

As more and more of the electronics industry finds a way to do the same work with light as it has done with electricity, the work of researchers like professor Capasso and his students at Harvard will find its way into production and use. Photonics is a widely researched field, but it still lies on the bleeding edge of technology and science. Look forward to more inventions and advances from it in the near and far future.