<title>Ultrahigh Resolution Laser Spectroscopy</title>

Abstract

Today, we have a new generation of spectroscopic tools that have such extremely high resolution capabilities that we are no longer limited by the so called "instrumental linewidth." In today's optical spectroscopy, the limit is more likely to be the natural or, in certain cases, the transit-time linewidth. To perform ultrahigh resolution spectroscopy one generally requires a tunable laser with a narrow spectral width, a means of reducing any mechanism that tends to broaden the spectral line under observation (e. g. , Doppler and collisional broadening) and, finally, a precise method of calibrating the tuning range of the laser. This paper will review the design of low-FM jitter lasers that can be precisely tuned, line-narrowing techniques including saturation, molecular beam and two-photon methods; and possible schemes for calibrating precisely the visible and infrared regions of the electromagnetic spectrum. Recent data in ultrahigh resolution spectroscopy will be presented.