The physics department has a broad program in Laser Physics including investigation of semiconductor lasers for communication and spectroscopy, high power diode lasers, ultrashort optical pulses, new optical materials and nonlinear optical processes. The program is closely interwoven with other departmental research, particularly the AMO Physics program described in an earlier section of this brochure.
A coordinated theoretical and experimental investigation of semiconductor lasers for optical communication, mid-infrared semiconductor lasers for spectroscopy, and high-power semiconductor lasers for fiber amplifiers is being carried out. Current research on semiconductor lasers for communication includes high-speed surface emitting laser research, 100 Gb/s pulse generation using mode-locking and optical multiplexing, investigation of integrated laser modulator structures and investigation of wavelength conversion using optical nonlinearities in semiconductor amplifiers. The high-speed transmission research is in collaboration with Bell Laboratories.
The research on mid-infrared lasers is aimed at spectroscopy for the detection of certain molecules. Current research is focused on the calculation of band structure parameters, and radiative and Auger recombination rates in semiconductor materials with the aim of understanding the high-temperature characteristics of these lasers. Very sensitive optoacoustic spectroscopic methods are under development in collaboration with Lincoln Labs.
A class 100 clean room for the fabrication of semiconductor lasers is being built jointly with the Photonics Research Center and Electrical Engineering Department. The clean room is equipped with dielectric deposition systems, metal deposition systems, a photolithography system, and cleaving and dicing equipment for laser fabrication. The fabrication facility also has a state-of-the-art molecular beam epitaxy (MBE) growth machine which is currently configured for the growth of GaAs and AlGaAs based materials.
The technology required to produce ultrashort laser pulses (< 50 fsec) with reasonable energy (1 mJ) has advanced rapidly over the past few years. We are actively engaged in further developing these laser systems with the goal of making them simpler and more reliable in order to extend their already broad range of applications. Most notably, we hold the record for the most energy extracted from an ultrashort pulse oscillator using the technique of cavity-dumping. This effort supports our work on studying the behavior of molecules in strong laser fields.
Current research on laser systems includes investigation of optical materials and of nonlinear optical processes. A coordinated theoretical and experimental effort is devoted to the study of loss mechanisms in transition-metal and lanthanide ions incorporated as impurity dopants in solid-state laser materials. A collaboration with the Research Laboratory for Crystal Physics of the Hungarian Academy of Sciences focuses on single crystals of paratellurite, zinc tungstate, and several bismuth oxides. A CO2 laser is used for laser-heated pedestal growth to synthesize new materials with novel optical properties. In nonlinear optics, research includes the investigation of nonlinear optical interactions in some of the materials just mentioned, as well as an extensive effort to develop new methods for generating and calibrating narrowband far-UV laser radiation. Improved laser amplifiers are under development in the Department, based both on solid state materials and broadly tunable laser dyes.