Atomic optics with tunable dye lasers

Abstract

Many new effects in optical physics and spectroscopy owe their origin to tunable dye lasers. Even if more practical and efficient tunable lasers are developed in the future, the remarkable role of the dye lasers in the advancement of science and technology cannot be overestimated. I would like to illustrate this statement with the example of the discovery of the methods for manipulating atomic motion by means of laser radiation, particularly the methods of the laserinduced optics of atomic beams. Incidentally, this area of laser-atomic physics will also be twenty five in two years. My interest in this problem was aroused in 1968 in connection with the search for new Doppler-free laser spectroscopic techniques. In the sixties, new Doppler-free laser absorption saturation spectroscopic methods were developed on the basis of the Lamb dip [11.1] and the inverted Lamp dip [11.2]. A shortcoming of this powerful technique is that it is capable of eliminating the linear Doppler broadening only in the quantum transition being saturated and in those coupled to it. I was aware of the fact that a principally different method existed to suppress the Doppler broadening, based on the restriction of the particle's motion within an area less than about 2 (radiation wavelength) across. This effect, referred to as the Lamp-Dicke regime [11.3], was successfully realized in the microwave band in the Ramsey hydrogen maser (storage bulb method) [11.4]. To implement such an approach in the optical region of the spectrum, I suggested [11.5] trapping atoms or molecules in small regions of space, less than ~'opt in size, by means of the so-called spatially periodic gradient force in a standing light wave (Fig. 11.1a). Thanks to the restriction (localization) of the atomic motion, there should have taken place a severe distortion of the Doppler profile with a narrow peak in its center, of all spectral lines observed along the axis of the standing light wave. I believed this method to hold much promise for high-resolution laser spectroscopy (in addition to saturation spectroscopy [11.1, 2] and two-photon spectroscopy in counter-propagating waves [ 11.6]) and called it the spectroscopy of trapped particles [11.7]. However, this idea, attractive as it was, could not be carried into effect without tunable lasers. I remember how, at the beginning of my research work at the Institute of Spectroscopy, Dr. O. Kompanets and myself made an attempt to