Ultra-broadband IR and THz generation and detection with ultrashort pulses

摘要

One of the most important techniques in modern optical science is the generation of phase-locked pulses. We review two different approaches to achieve the broadband generation and detection: photoconductive antenna and air-plasma method, and show the application to spectroscopy. We investigated dependences of the detection sensitivity on the growth and annealing conditions of antenna substrate, antenna structure, and the gate pulse duration. We successfully generated ultra-broadband phase-locked pulses in the terahertz and infrared regions (up to ～200 THz) using a combination of organic nonlinear crystals and 5-fs ultrashort laser pulses, which is directly detected by an optimized photoconductive antenna. With a combination of air plasma and intense 10-fs pulses, we also achieved the generation and detection of ultra-broadband phase-locked pulses continuously from the terahertz region to the near-infrared region. The methods are applied to the spectroscopy of superconducting gaps. Our results demonstrate that the broadband phase-locked pulses can easily be generated and detected without explicit carrier envelope phase stabilization, and can be used for broadband spectroscopy.