Figure 1
From: Single molecule DNA detection with an atomic vapor notch filter
![Figure 1](http://media.springernature.com/full/springer-static/image/art%3A10.1140%2Fepjqt%2Fs40507-015-0033-1/MediaObjects/40507_2015_33_Fig1_HTML.gif)
Experimental configuration. (a) Single stranded DNA under study, labeled at the 5’-end with the organic dye ‘Atto590’. (b) Confocal and wide-field microscope. The filter configuration can be changed in approx. 1 s. WF = wide-field configuration; APD = avalanche photo diode; LP-filter = long-pass filter; CCD = charged coupled device, camera; (c) Laser emission and filter function of the commercial long pass filter. OD = optical density; (d) Spectrum of the sodium reference cell scanning over the D2 resonance frequency. The purple line shows the Doppler-free difference laser lock signal. The blue line shows the measured absorption spectrum of the atomic vapor cell at 200°C. The block band is approx. 6 GHz broad and shows an optical rejection of more than 6 orders of magnitude (measured). The calculated optical density is much higher (OD 100).