A single-mode external cavity diode laser using an intra-cavity atomic Faraday filter with short-term linewidth <400 kHz and long-term stability of <1 MHz

Abstract

We report on the development of a diode laser system - the "Faraday laser" - using an atomic Faraday filter as the frequency-selective element. In contrast to typical external-cavity diode laser systems which offer tunable output frequency but require additional control systems in order to achieve a stable output frequency, our system only lases at a single frequency, set by the peak transmission frequency of the internal atomic Faraday filter. Our system has both short-term and long-term stability of less than 1 MHz, which is less than the natural linewidth of alkali-atomic D-lines, making similar systems suitable for use as a "turn-key" solution for laser-cooling experiments.

ElecSus: Extension to arbitrary geometry magneto-optics

“…In this subsection we consider the application of field gradients to Faraday filtering. In reference [9], a Faraday filter with high peak transmission was demonstrated with an approximately uniform axial magnetic field, produced by placing the 5 mm vapour cell between two NdFeB ring magnets, separated by a large distance compared to their extent, and the extent of the vapour cell. For applications development, using a smaller, single magnet system to generate the field is attractive for mechanical simplicity, miniaturisation purposes and cost-saving.…”

“…9: field maximum/minimum over the cell: 222 G / 178 G), when compared with the filter profile used in ref. [9] (dashed line in fig. 9).…”

“…The fundamental interaction between atoms and light continues to underpin a great deal of scientific research. In atomic vapours, understanding and control over this interaction has enabled a vast array of applications, including compact atomic clocks [1], magnetometers [2,3], magnetoencephalography [4,5], thermometry [6], laser frequency stabilisation both on [7] and off-resonance [8,9], enhanced frequency up-conversion [10], trans-spectral orbital angular momentum transfer [11] and quantum memories [12].…”

A Faraday laser operating on Cs 852 nm transition

“…In recent years, the concept of Faraday laser is formally proposed and named [57][58][59][60]. The Faraday laser system uses the ARLD as the gain medium and the Faraday optical filter as the frequency selective device.…”

Optimized ultra-narrow atomic bandpass filters via magneto-optic rotation in an unconstrained geometry

“…These optimized filters could find use in many of the areas where Faraday filters are currently used, with little modification to the optical setup, allowing for improved performance with relatively little change. Magneto-optic effects in atomic media continue to be used in a vast array of applications, such as magnetometry [1,2], quantum hybrid systems integrating quantum dots with atomic media [3], microwave detection and imaging [4,5], optical isolators [6], and self-stabilizing laser systems [7][8][9]. Of particular interest are narrow optical bandpass filters [10][11][12][13][14][15], which is the subject of this Letter.…”