Ultranarrow line filtering using a Cs Faraday filter at 852 nm

Abstract

To achieve quantum-noise-limited performance, background-limited laser receivers require narrow-band optical filters. We measured and modeled the ultranarrow-band transmission spectrum of a Cs Faraday filter at 852 nm. The transmission spectrum consisted of passbands on either side of the 6 (2)S((1/2))-6 (2)P(3/2) hyperfine doublet lines, making a total of four. The passbands may be simple peaks or highly modulated, depending on the operating parameters. We observed peaked passbands of near-unity transmission with a 0.6-GHz bandwidth and modulated bands with features as sharp as 100 MHz. Excellent agreement with our calculations at 852 nm allows us to predict confidently a 0.7-GHz transmission band for Cs at 455 nm.

A gigahertz-bandwidth atomic probe based on the slow-light Faraday effect

“…Appropriate choice of atomic species and laser wavelength opens up the possibility of submarine (at ∼ 450 nm) [17] and fibre-optic (at ∼ 1.53 µm) communications at the large bit rates required for rapid data transfer.…”

“…Large rotations of above π rad are seen close to resonance, and even at detunings of many GHz the difference in transmission is noticeable. The rapid oscillation in the polarisation as a function of frequency has a number of applications such as a polarisation switch, optical isolator or narrowband filter [17]. By using isotopically pure Rb cells one could use one isotope to realise a device that works on resonance for the other isotope.…”

“…A magnetic field applied to such a medium can produce rotations of greater than π/2 rad without significant absorption. As the rotation is controlled by the applied field the effect can be used as a tunable frequency filter [17]; and for pulsed light it can lead to pulse splitting [18].…”

The Faraday filter-based spectrometer for observing sodium nightglow and studying atomic and molecular oxygen associated with the sodium chemistry in the mesopause region

“…Subsequent studies using a variety of atomic species have been performed (Dick and Shay, 1991;Menders et al, 1991;Chan and Gelbwachs, 1993). For Na, filters were developed by Agnelli et al (1975) and Chen et al (1993), with further studies into cell transmission by Hu et al (1998).…”

Atomic Faraday filter with equivalent noise bandwidth less than 1 GHz

“…These atomic Faraday filters are imaging filters [9] with a large field of view [10], and can be engineered to be low loss at the signal frequency [11]. This makes them the filter of choice for many applications, for example, they are used in atmospheric lidar [11][12][13][14] [9,24,25,[31][32][33][34], potassium [18,35,36], rubidium [37][38][39], and cesium [23,40,41]. A Faraday filter on the cesium D 1 line (894 nm) could be useful for quantum optics experiments which utilize the the Cs D 1 line [42], and could aid filtering degenerate photon-pairs at 894 nm in a similar way to that shown for 795 nm [21].…”