Journal of Luminescence 127 (2007) 110–115 Wideband RF spectral analyzer based on spectral-spatial holography in Tm 3þ :YAG achieved with a highly stabilized frequency chirped laser G. Gorju à , V. Crozatier, I. Lorgere´, J.-L. Le Goue¨t, F. Bretenaker Laboratoire Aime´Cotton, C.N.R.S., Univ. Paris Sud, Baˆtiment 505, 91405 Orsay Cedex, France Available online 28 February 2007 Abstract We demonstrate a 10 GHz spectrum analyzer with MHz resolution and a 30 dB dynamic range using the spectral hole burning (SHB) Tm 3þ :YAG crystal working at 793 nm. Thanks to the fast and linear chirping capabilities of the laser used, it has a potential 100% probability of interception and a response time in the ms range. The system is compared to a previously demonstrated SHB spectral analyzer. We also investigate theoretically and experimentally the requirements for the frequency chirped laser sources spectral purity and their influences on the precision of our experiment. r 2007 Elsevier B.V. All rights reserved. Keywords: Rare earth; Thulium; Spectral analysis 1. Introduction Radar signal processing or (sub) millimeter astronomy needs very sensitive processing techniques to analyze signals spanning GHz of bandwidth with 100% probability of interception. Because optoelectronic solutions present broad bandwidth capabilities more naturally than electro- nics, they are under active development for Radio Frequency (RF) signals spectral analysis. At the moment the most widely used optoelectronic spectrometer is the acousto-optic spectrometer (AOS) [1]. However, the bandwidth of this device is currently limited to 2 GHz. Furthermore, these spectrometers must be designed with fixed bandwidth and resolution. Consequently, they are not flexible regarding different kinds of observations. In order to cope with the increasing bandwidth demand, one needs an alternative technology with great potential for future laboratory experiments. The emerging spectral hole burning (SHB) technologies have the potential to treat large bandwidth signals. In particular, the inhomogeneous broadened absorption bands of rare-earth-doped crystals can have bandwidths that exceed tens of GHz together with a spectral resolution well below 100 kHz at cryogenic temperature [2]. A spectral analyzer exploiting the wide bandwidth potentialities of SHB has been first demonstrated by Lavielle et al. [3]. Quite similarly to an AOS, this setup spatially separates different RF spectral components. This architecture has demonstrated 3.3 GHz bandwidth, sub-MHz resolution and zooming capability. However, it suffers from two main drawbacks: (i) its spatial demultiplexing principle makes the channel capacity difficult to increase; (ii) its optical scheme is rather complicated to implement. Recently a more direct and completely different approach called ‘‘photographic scheme’’ based on Tm 3þ :YAG crystal SHB spectrum analyzer has been developed [4,5]. It consists in engraving the optically carried RF signals to be analyzed in the populations of the rare-earth-ions by SHB phenomenon and to read the spectra with a chirped laser. Both systems have demonstrated a 10-GHz band- width with 10 000 channels capacity and a resolution in the MHz range [4,5]. The weakness of the ‘‘photographic scheme’’ spectral analyzer is its dynamic range of 20 dB which is limited by the presence of a large background signal. We consider we are within the dynamic range as long as the signal amplitude varies linearly with the engraving RF power. In order to improve this figure while ARTICLE IN PRESS www.elsevier.com/locate/jlumin 0022-2313/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jlumin.2007.02.015 à Corresponding author. E-mail address: guillaume.gorju@lac.u-psud.fr (G. Gorju).