SC301 Quantum Cascade Lasers: From Band Structure Engineering to Commercialization

Sunday, May 4, 1:30 p.m. - 4:30 p.m.
Federico Capasso; Harvard Univ., USA

Course Description
Quantum Cascade Lasers (QCLs), first demonstrated in 1994 at Bell Labs, are fundamentally different from diode lasers due to their physical operating principle, which makes it possible to design the wavelength over a wide range by simple tailoring of active region layer thicknesses, and to their unipolar nature. These features have revolutionized the field of semiconductor lasers particularly in the mid-infrared region of the spectrum (where molecules have their absorption fingerprints) and in the far-infrared or so called Terahertz spectrum. In these regions until the advent of QCLs there were no semiconductor lasers capable of room temperature operation in pulsed or cw, as well as high output power and stable/wide single mode tunability. The unipolar nature of QCL, combined with the capabilities of bandstructure engineering leads to unprecedented design flexibility and functionality compared to other lasers.

The physics of QCLs, design principles, supported by modeling, will be discussed along with the electronic, optical and thermal properties. State-of-the-art performance in the mid-ir and Terahertz will be reviewed. A broad range of applications (chembio sensing, trace gas analysis, atmospheric chemistry, medical and combustion diagnostics, THz imaging, etc.) and their ongoing commercial development will be discussed. Finally, the course will cover exciting developments such as new light-sources that uses the giant resonant nonlinear susceptibilities of quantum engineered structures to achieve high conversion efficiency at satellite wavelengths, ultrabroadband lasers, ultrashort pulse operation, photonic crystal QCls, optofluidic QCLs as well as QCL incorporating optical antennas on the laser facets to achieve well below wavelength spatial resolution for near field applications.

Benefits and Learning Objectives
This course should enable you to:

• Study intersubband transitions and underlying QC Laser physics, operating principles and fundamental differences between standard semiconductor lasers and QC lasers.
• Understand the rudiments of band structure engineering, including the quantum design of the key types of QC lasers, which have entered real world applications.
• Discuss experimental device performance, including physical limits, design constraints and comparison with theory.
• Discuss the basics of QC laser device technology: fabrication process, materials growth options.
• Illustrate the basics of a chemical sensing system.
• Discuss applications of state-of the-art mid-infrared QC lasers to sensing and present several examples of QC laser commercialization.
• Discuss the current research frontier of QC lasers: multiwavelength and broadband devices, nonlinear optical QC lasers; TeraHertz QC lasers, ultrashort pulse QC lasers, optofluidic and photonic crystal QC lasers.
• Summarize a comprehensive future outlook on QC laser physics, device performance and system applications. Assessment of QC laser technology market.

Intended Audience
Researchers in industry, academia and government labs; technical managers. Graduate students; qualified undergraduates (mostly senior level) majoring in EE or physics/applied physics.

Instructor Biography
Federico Capasso is the Robert L. Wallace Professor of Applied Physics and the Vinton Hayes Senior Research Fellow in Electrical Engineering at Harvard. Previously he held positions at Bell Labs as a member of technical staff, department head and physical research vice president. He and his group invented and first demonstrated QC lasers. He has been active in this field for 12 years, including collaborations with industry and tech transfer. His many honors include the King Faisal Prize, the APS Schawlow Prize, the IEEE Edison Medal, the OSA R. Wood Prize and membership in NAS and NAE.