Complete hyperfine Paschen-Back regime at relatively small magnetic fields realized in Potassium nano-cell

A one-dimensional nano-metric-thin cell (NC) filled with potassium metal has been built and used to study optical atomic transitions in external magnetic fields. These studies benefit from the remarkable features of the NC allowing one to use $\lambda/2$- and $\lambda$-methods for effective investigations of individual transitions of the K D_1 line. The methods are based on strong narrowing of the absorption spectrum of the atomic column of thickness L equal to $\lambda/2$ and to $\lambda$(with \lambda = 770\un{nm} being the resonant laser radiation wavelength). In particular, for a $\pi$-polarized radiation excitation the $\lambda$-method allows us to resolve eight atomic transitions (in two groups of four atomic transitions) and to reveal two remarkable transitions that we call Guiding Transitions (GT). The probabilities of all other transitions inside the group (as well as the frequency slope versus magnetic field) tend to the probability and to the slope of GT. Note that for circular polarization there is one group of four transitions and GT do not exist. Among eight transitions there are also two transitions (forbidden for $B$ = 0) with the probabilities undergoing strong modification under the influence of magnetic fields. Practically the complete hyperfine Paschen-Back regime is observed at relatively low (\sim 1\un{kG}) magnetic fields. Note that for K $D_2$ line GT are absent. Theoretical models describe the experiment very well.Comment: 6 page

Giant modification of atomic transitions probabilities induced by magnetic field: forbidden transitions become predominant

Magnetic field-induced giant modification of probabilities for seven components of 6S1/2 (Fg=3) - 6P3/2 (Fe=5) transition of Cs D2 line forbidden by selection rules is observed experimentally for the first time. For the case of excitation with circularly-polarized laser radiation, the probability of Fg=3,mF=-3 - Fe=5,mF=-2 transition becomes the largest among 25 transitions of Fg=3 - Fe=2,3,4,5 group in a wide range of magnetic field 200 - 3200 G. Moreover, the modification is the largest among D2 lines of alkali metals. A half-wave-thick cell (length along the beam propagation axis L=426 nm) filled with Cs has been used in order to achieve sub-Doppler resolution which allows for separating the large number of atomic transitions that appear in the absorption spectrum when an external magnetic field is applied. For B > 3 kG the group of seven transitions Fg=3 - Fe=5 is completely resolved and is located at the high frequency wing of Fg=3 - Fe=2,3,4 transitions. The applied theoretical model very well describes the experimental curves.Comment: 7 pages, 8 figure

Figure 1: Direct Conversion Receiver DC OFFSET SUPPRESSION IN DOUBLE BALANCE DIRECT CONVERSION RECEIVERS

Abstract The double balance mixer scheme in-phase signal input and double-quadrature Local Oscillator (LO) is suggested for application on IQ direct conversion receivers. The influence of the gain and phase mismatches of splitters is investigated. It is shown that a similar scheme using square-law detectors is promising on optical applications

PECULIARITIES OF RESONANT ABSORPTION AND FLUORESCENCE IN EXTREMELY THIN CELL FILLED WITH Rb AND BUFFER GAS.

Recently unique extremely thin cells (ETC) containing atomic vapour of alkali metals with the column thickness L of an order and much less than optical light wavelength λ have been developed. It has been demonstrated that these ETC are a very promising tool for a fundamental study of atom-light, atom-atom, atom-surface and atom-external magnetic field interactions. Particularly, a dramatically different behaviour of resonant absorption, fluorescence and resonant magneto-optical processes compared to that obtained with the help of cm-long ordinary cells has been demonstrated. Possible applications based on ETC are described, such as magnetometers with nanometric spatial resolution and tunable atomic frequency references. For the study of buffer gas influence, a multi-region cell (MRC) has been developed. MRC consists of an ETC cell having a wedged thickness of the gap between the windows that allows one to form atomic vapour column thickness in the range of 0.1 ÷ 4 μm. The ETC is connected through a sapphire tube with a 1cm-long sapphire tube having sapphire windows. The 1cm-long cell has a sapphire side-arm containing Rb metal. MRC's are filled with 6 Torr and 20 Torr Neon gas, thus there is Rb vapour and buffer gas inside the MRC. The construction of the MRC allows one to compare absorption and fluorescence processes simultaneously in the case of the ETC use as well as in the case of 1cm-long ordinary cell use. The comparison of the resonant absorption and fluorescence in the extremely thin cell (ETC) filled with pure Rb with another one filled with Rb and Neon gas with the pressures of 6 Torr and 20 Torr is provided. The effect of the collapse and revival of Dicke-type narrowing is still observable for the thicknesses L = λ/2, and L = λ, with λ being the resonant laser wavelength 794 nm (D1 line of Rb), i.e. the spectra of the resonant absorption and fluorescence demonstrate strong sub-Doppler narrowing for the thickness L = λ/2 and broadening for the thickness L = λ. It is important to note that in an ordinary Rb cell with the thickness L in the range of 1mm - 10 cm filled with buffer gas, with the pressure higher than 1 Torr, in the well-known Saturation Absorption scheme, any sub-Doppler features are absent. For L = λ the so called velocity selective optical pumping/saturating resonance (VSOP) located at the atomic transition is still observable when Ne pressure is 6 Torr, while the linewidth is increased by 4 times in comparison with that obtained in a pure Rb ETC. It is also demonstrated that the use of the fluorescence spectra at L = λ/2 allows one to use ETC for the buffer gas pressure measurements. Comparison with the theory will be presented