Federico Capasso - Biography#

Federico Capasso was one of the inventors of the quantum cascade laser during his work at Bell Laboratories. He is currently on the faculty of Harvard University. He has co-authored over 450 papers, edited four volumes, and holds over 60 US patents.

Federico Capasso received the doctor of Physics degree, summa cum laude, from the University of Rome, Italy, in 1973 and after doing research in fiber optics at Fondazione Bordoni in Rome, joined Bell Labs in 1976. In 1984, he was made a Distinguished Member of Technical Staff and in 1997 a Bell Labs Fellow. In addition to his research activity Capasso has held several management positions at Bell Labs including Head of the Quantum Phenomena and Device Research Department and the Semiconductor Physics Research Department (1987–2000) and Vice President of Physical Research (2000–2002). He joined Harvard on January 1, 2003.

He and his collaborators made many wide ranging contributions to semiconductor devices, pioneering the design technique known as band-structure engineering. He applied it to novel low noise quantum well avalanche photodiodes, heterojunction transistors, memory devices and lasers. He and his collaborators invented and demonstrated the quantum cascade laser (QCL) (Faist, J; Capasso, F; Sivco, DL; Sirtori, C. ; Hutchinson, Al; Cho, AY "Quantum Cascade Laser" Science 264, 553-556 (1994)) . Unlike conventional semiconductor lasers, known as diode lasers, which rely on the band gap of the semiconductor to emit light, the wavelength of QCLs is determined by the energy separation between conduction band quantized states in quantum wells. In 1971 researchers postulated that such an emission process could be used for laser amplification in a superlattice (Kazarinov, RF; Suris, RA (April 1971). "Possibility of amplification of electromagnetic waves in a semiconductor with a superlattice". Fizika i Tekhnika Poluprovodnikov 5 (4): 797–800). The QCL wavelength can be tailored across a wide range from the mid-infrared to the far infrared by changing the quantum well thickness. The mature technology of the QCL is now finding commercial applications.[2]] QCLs have become the most widely used sources of mid-infrared radiation for chemical sensing and spectroscopy and are commercially available. They operate at temperatures in excess of 100 C and emit up to several Watts of power in continuous wave.

Capasso's current research in quantum electronics deals with very high power cw QCLs, the design of new light sources based on giant optical nonlinearities in quantum wells such as widely tunable sources of terahertz radiation based on difference frequency generation and with plasmonics. He and his group at Harvard have demonstrated a new class of optical antennas and plasmonic collimators that they have used to design the near-field and far-field of semiconductor lasers, achieving ultrahigh intensity deep subwavelength size laser spots, laser beams with greatly reduced divergence and multibeam lasers. His group showed that suitably designed plasmonic interfaces consisting of optically thin arrays of optical antennas lead to a powerful generalization of the centuries old laws of reflection and refraction. They form the basis of "flat optics" based on metasurfaces.

Federico Capasso has made major contributions to the study of quantum electrodynamical forces known as Casimir forces. He used the Casimir effect (the attraction between metal surfaces in vacuum due to its zero point energy) to control the motion of MicroElectroMechanical Systems (MEMS). He demonstrated novel devices (Casmir actuators and oscillators), setting limits to the scaling of MEMs technology and with his collaborators Jeremy Munday and Adrian Parsegian was the first to measure a repulsive Casmir force.