Spectral narrowing broadens applications

Yanhong Xiao

Electromagnetically induced transparency (EIT) can make an otherwise opaque medium transparent by utilizing quantum coherence. EIT has attracted great interest since the 1990s for its wide applications in metrology, nonlinear and quantum optics, and quantum information science. We present a review on spectral line narrowing mechanisms in EIT-related systems, accounting for linewidths much narrower than expected from the standard mechanisms of Doppler broadening, transit time broadening, magnetic field inhomogeneity and power broadening. Topics covered include Dicke narrowing, atomic-motion-induced Ramsey narrowing, motional narrowing, density narrowing, laser induced narrowing and power-broadening-free resonance. Intuitive pictures are provided to describe the essential physics of each mechanism.

Yoav Sagi, Rami Pugatch, Ido Almog +1 more

A.L.J. Burgmans, Martin F. H. Schuurmans

Urs P. Wild, Alois Renn

The lowest electronic transitions of many absorbing centers in solid hosts consist of extremely narrow zero phonon lines distributed over a broad spectral range. Frequency selective modification of such inhomogeneously broadened bands has several potential applications. In very dilute samples inhomogeneous broadening provides a key for spectroscopic isolation of single absorber resonances.

Aloïs Würger

Xiuji Lin, M. T. Hartman, Philippe Goldner +3 more

We explore the properties of ultra-narrow spectral holes in ensembles of solid-state emitters in crystals over a range of sub-kelvin temperatures, with a focus on their potential application in frequency stabilization schemes as an alternative to ultrastable cavities. We investigate how the parameters used to burn the spectral hole impact its shape, and how these factors determine the minimum achievable linewidth. In addition to the stability of the hole's center frequency, the linewidth and contrast play a crucial role in frequency locking. At sub-kelvin temperatures, the temperaturedependent T^7 broadening from two-phonon Raman scattering is expected to be negligible, and the spectral hole's linewidth should therefore remain constant in this interval. We observe however a linear broadening with increasing temperature, highlighting the need for further investigation into the mechanisms governing the linewidth at ultra-low temperatures.