Purely electronic zero-phonon line as the foundation stone for high-resolution matrix spectroscopy, single-impurity-molecule spectroscopy, and persistent spectral hole burning. Recent developments

Abstract

A few examples of recent progress in the study and applications of purely electronic zerophonon line (ZPL) and its offshoots are briefly considered: new experimental values of the narrowest ZPL; time-and-space-domain holography in the femtosecond domain, and the realization of a femtosecond Taffoli gate by it; single-impurity-molecule spectroscopy, its relation to single-photon interference and to the realization of quantum computing; the promises of quantum computing compared to what has already been done in holography. PACS: 33.70.JgThe purely electronic zero-phonon line (ZPL) is a remarkable feature of low-temperature spectra of the absorption and luminescence of quite a number of various impurity centers in various solid hosts (see [1][2][3][4][5] and references therein). ZPLs can be very narrow and have very high peak absorption cross sections. These valuable properties, as well as several other features, are in close correspondence with features of the Möss-bauer g-resonance line. Because of this correlation, originating from the symmetry of the harmonic oscillator Hamiltonian in coordinate and momenta [6], J.F. Gross called the ZPL the optical analog of the Mössbauer line [7], helping considerably to popularize optical ZPLs.I must note that two main features of the optical ZPL were pointed out in [8], five years before the first publication by Mössbauer [9]. That result of this early paper, however, was not given due attention.ZPLs, as sharp and intense features in the low-temperature spectra of some impurities in solids (without detailed explanation of their properties), were found and fruitfully studied experimentally years before the Mössbauer effect. ZPL widths of around 1 cm -1 were measured in the spectra of rare-earth impurity ions introduced in proper ionic single-crystal hosts and also ruby (see [10,11] and references therein). The new wave of theoretical studies brought the understanding that even the very narrow widths of around 1 cm -1 are essentially inhomogeneous widths [1,2,5,12,13]. It was predicted that for dipole-allowed transitions the homogeneous lines should be, at liquid helium temperatures, another 3-4 orders of magnitude narrower still, i.e., the homogeneous linewidth is 10 -3 --10 -4 cm -1 » 10-100 MHz (see [5,[12][13][14] and references therein), and even a few orders of magnitude narrower yet for forbidden ones. The theoretical point, later confirmed experimentally [12,14] was that the ZPL's homogeneous width, G hom (T), tends in the limit T ® 0 to the value determined by the lifetime of the excited electronic state.This theoretical prediction stimulated experimentalists to search for methods of how to eliminate or use the inhomogeneous broadening and to utilize the precious properties of ZPLs in the frequency domain.ZPL became the foundation stone for three novel fields of modern optics and spectroscopy [3,4,15]: (1) very high spectral resolution ZPL studies of atoms and molecules as impurities in low-temperature solids (very high spectral resolution matrix isolation spectrosco...

Theoretical modeling of single-molecule fluorescence with complicated photon statistics

“…Soon after work on single-molecule spectroscopy (SMS) was published [1,2], it became clear that the optical line of a single chromophore molecule embedded in an amorphous matrix such as a polymer or glass can serve as an effective tool for studying the quantum dynamics of the environment of the guest molecule. It is well known that the optical spectrum of a single chromophore consists of a narrow zero-phonon line (ZPL) and a phonon sideband (PSB) [3]. The spectral position of the ZPL is sensitive to the quantum state of the environment of the dopant molecule.…”