all Federico Capasso stories

Researchers see exotic force for first time

404132862 — Tue, 06 Jan 2009 18:09:52 -0500

For the first time, researchers have measured a long-theorized force that operates at distances so tiny they’re measured in billionths of a meter, which may have important applications in nanotechnology as scientists and engineers seek new ways to create devices far too small for the eye to see.

The advance, by researchers by Harvard and National Institutes of Health (NIH) researchers, used a novel combination of materials to create a repulsive Casimir force, which pushes apart certain materials when separated by distances so tiny — between 20 nanometers and 100 nanometers — that they’re nearly touching.

Scientists demonstrate highly directional semiconductor lasers

404132862 — Thu, 24 Jul 2008 13:42:02 -0400

Applied scientists at Harvard collaborating with researchers at Hamamatsu Photonics in Hamamatsu City, Japan, have demonstrated, for the first time, highly directional semiconductor lasers with a much smaller beam divergence than conventional ones. The innovation opens the door to a wide range of applications in photonics and communications. Harvard University has also filed a broad patent on the invention.

Creating semiconductor lasers

404132862 — Thu, 24 Jul 2008 13:45:57 -0400

Lasers are often considered to be highly directional light sources:
their beams are able to propagate over long distances without
substantial spreading. This, however, is not always the case.
Semiconductor lasers, the most commonly used among all lasers, suffer
from a large beam divergence. Such divergence is governed by the
principle of diffraction, which predicts bending and spreading of light
around small obstacles or apertures. Light beams endure strong
diffraction when emerging from the small light-emitting regions of
semiconductor lasers (the dimensions of which are comparable to the
laser wavelength). This leads to a beam divergence angle of tens of
degrees for most semiconductor lasers.

Researchers develop new technique for fabricating nanowire circuits

404132862 — Thu, 26 Jun 2008 12:11:39 -0400

Scientists at Harvard's School of Engineering and Applied Sciences (SEAS), collaborating collaborating with researchers from the German universities of Jena, Gottingen, and Bremen, have developed a new technique for fabricating nanowire photonic and electronic integrated circuits that may one day be suitable for high-volume commercial production.

Compact, wavelength-on-demand Quantum Cascade Laser chip created

404132862 — Tue, 05 Feb 2008 16:10:50 -0500

Engineers at Harvard's School of Engineering and Applied Sciences have demonstrated a highly versatile, compact and portable Quantum Cascade Laser sensor for the fast detection of a large number of chemicals, ranging from infinitesimal traces of gases to liquids, by broad tuning of the emission wavelength. The potential range of applications is huge, including homeland security, medical diagnostics such as breadth analysis, pollution monitoring, and environmental sensing of the greenhouse gases responsible for global warming.

Laser advance could open up new markets

Fri, 13 Jul 2007 10:40:24 -0400

Applied scientists from Harvard University have, for the first time, demonstrated high-power continuous wave (cw) room-temperature quantum cascade (QC) lasers made by a well-established mass production semiconductor synthesis technique. The breakthrough could soon lead to the large-scale commercialization of QC lasers and open up new markets for laser-based chemical sensors.

The new generation of QC lasers relies on a layer deposition technique known as Metallorganic Vapor Phase Epitaxy (MOVPE), one of the most common and versatile methods for mass-producing technology for semiconductor lasers, circuits, and other photonics components for communications.

Harvard scientists develop 'plug and play' laser

50443248 — Wed, 25 Jul 2007 12:46:53 -0400

Engineers and applied physicists have demonstrated the feasibility of a new type of plug-in laser that could lay the groundwork for wide-ranging security applications.
Their Raman injection laser, described in the most recent issue of the journal Nature, combines the advantages of nonlinear optical devices and semiconductor injection lasers with a compact "plug and play" design.

"While our paper merely demonstrates proof of concept, one day it may lead to the sort of security experts dream of having: a portable device that you could use to detect things like weapons or explosives simply by shining an invisible light to see what someone might be hiding," says Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering in Harvard University's Division of Engineering and Applied Sciences. "The work also represents an important advance in quantum design since we are now able to engineer, from the bottom-up, a new Raman material and laser, and tailor its property for a given application."

While Raman lasers have been used for a long time, they have generally required a large and powerful pump to compensate for the beam's weakening as it propagates through a material. In their work, Capasso and his colleagues were able to combine the pump and the material itself in a single device.

Conventional Raman lasers depend on a fundamental phenomenon in physics called the Raman effect: the change in the frequency of monochromatic light, such as that found in a laser, when it passes through a substance. When light from an intense laser beam, known as the "pump," deflects off the molecules of certain materials, some of the incident photons lose part of their energy. As a result, a secondary laser beam, with a frequency shifted from that of the first, emerges from the material.

By combining the power source and the Raman material together, literally creating a laser-within-a-laser, the team has created the first current-driven Raman laser. The current generates an internal laser beam within a material, which, in turn, generates the Raman laser radiation. Because the pump laser is now self-generated, the device is highly efficient, reducing the standard decline that happens when an external power source is used.