A Stark anomalous dispersion optical filter (SADOF) is an ultra-narrow bandwidth optical filter for applications in laser remote sensing and satellite laser communications. A SADOF consists of an atomic vapor cell between crossed polarizers subject to a dc electrical field transverse to the optical path and oriented 45° relative to the crossed polarizers. When linearly polarized light travels through a rubidium atomic vapor cell, a polarization rotation occurs (Stark induced birefringence). Large rotation angles may be obtained when the input light frequency is near the resonant frequencies of the atomic vapor. The transmission peaks of the SADOF correspond to frequencies that have rotation angles of odd integer multiples of π/2 and low absorption in the vapor cell. The transmission curve depends on the electric field and atomic density, and the optimum conditions for a rubidium SADOF are found through theoretical calculations that include both Stark spectral and polarization rotation. We will present theoretical SADOF transmission curves for several green rubidium transition frequencies.
A Stark anomalous dispersion optical filter (SADOF) is an ultra-narrow bandwidth optical filter for applications in laser remote sensing and satellite laser communications. A SADOF consists of an atomic vapor cell between crossed polarizers subject to a dc electrical field transverse to the optical path and oriented 45° relative to the crossed polarizers. When linearly polarized light travels through a rubidium atomic vapor cell, a polarization rotation occurs (Stark induced birefringence). Large rotation angles may be obtained when the input light frequency is near the resonant frequencies of the atomic vapor. The transmission peaks of the SADOF correspond to frequencies that have rotation angles of odd integer multiples of π/2 and low absorption in the vapor cell. The transmission curve depends on the electric field and atomic density, and the optimum conditions for a rubidium SADOF are found through theoretical calculations that include both Stark spectral and polarization rotation. We will present theoretical SADOF transmission curves for several green rubidium transition frequencies.
A Rb 532 nm Stark anomalous dispersion optical filter consists of an atomic vapor cell between crossed polarizers subjected to an electrical field transverse to the optical path, and a constant magnetic field along the optical path. The color glass filters are used to reject the infrared radiation. The 795 nm optical pumping is needed to populate the lower level of the filter transition. When linearly polarized light travels through a dispersive atomic vapor cell, a polarization rotation occurs. This polarization rotation is mainly due to the resonant Faraday effect.>
The potassium tunable excited state Stark anomalous dispersion optical filter (SADOF) at 532.33 nm was studied theoretically and experimentally. The theoretical model of SADOF was deduced and the transmission of SADOF was calculated. The transmission spectra of potassium SADOF in different electric fields were measured and the experimental frequency shifts of SADOF versus the strengths of the electric field were given. Furthermore, the comparison between the experimental results with the corresponding theoretically simulated results has been completed. The comparison shows that our experimental results agree with the theoretically simulated results in general.
Narrow-band optical filtering is required in many spectroscopy applications to suppress unwanted background light. One example is quantum communication where the fidelity is often limited by the performance of the optical filters. This limitation can be circumvented by utilizing the GHz-wide features of a Doppler broadened atomic gas. The anomalous dispersion of atomic vapours enables spectral filtering. These, so-called, Faraday anomalous dispersion optical filters (FADOFs) can be by far better than any commercial filter in terms of bandwidth, transition edge and peak transmission. We present a theoretical and experimental study on the transmission properties of a sodium vapour based FADOF with the aim to find the best combination of optical rotation and intrinsic loss. The relevant parameters, such as magnetic field, temperature, the related optical depth, and polarization state are discussed. The non-trivial interplay of these quantities defines the net performance of the filter. We determine analytically the optimal working conditions, such as transmission and the signal to background ratio and validate the results experimentally. We find a single global optimum for one specific optical path length of the filter. This can now be applied to spectroscopy, guide star applications, or sensing.
To obtain the weak signal light detection from the high background noise,a study on ultra-narrow bandwidth Faraday anomalous dispersion optical filter(FADOF) at the 87Rb D1 line,5S1/2F=2→5P1/2 F′=1transmission(795 nm) is demonstrated experimentally.A sample cell filled with Rubidium atoms in which the proportion of 87Rb is greater than that of the nature rubidium is placed in a homogeneous magnetic field between two crossed Glan-Thompson polarizers.The incident probe light goes through the sample cell,and interacts with the atoms.Because of the Faraday rotation,the function of the filter can be realized.When the experiment condition changed,the result of transmission spectrum changed accordingly.With the temperature rising from 340 K to 360 K,the variation of the transmission spectrum is recorded particularly.And the reason for the variation is analyzed carefully.At a proper temperature and magnetic field,a transmission spectrum narrowed to ~220 MHz is obtained,and the peak transmission is about 48%.The performance of the87Rb D1 line is better than that of the 85Rb.
The characteristics of a potassium Faraday anomalous dispersion optical filter operating on the blue and near infrared transitions are calculated. The results show that the filter can be designed to provide high transmission, very narrow pass bandwidth, and low equivalent noise bandwidth. The Faraday anomalous dispersion optical filter (FADOF) provides a narrow pass bandwidth (about GHz) optical filter for laser communications, remote sensing, and lidar. The general theoretical model for the FADOF has been established in our previous paper. In this paper, we have identified the optimum operational conditions for a potassium FADOF operating on the blue and infrared transitions. The signal transmission, bandwidth, and equivalent noise bandwidth (ENBW) are also calculated.