The Spectral Hole Burning (SHB) technology is considered for >10 GHz instantaneous bandwidth signal processing applications. In this context we report on the first demonstration of a SHB microwave spectrometer. The present setup is confined to narrow bandwidth operation.optical processing since it offers outstanding performance in terms of bandwidth and time-bandwidth product. Various optical functions, such as time-domain correlation[2, 31, real-time data routing[4, 51 and truetime delay generation for radar application [6], have been demonstrated recently that illustrate SHB signal processing potential.Much attention has been dedicated to far infrared and sub-millimeter spectroscopy in recent or planned space observatories[ 11. In a sub-millimeter system the input signal undergoes frequency downshifting before reaching the back-end spectral analyzer. The most widely used spectrometers in radio astronomy are the acousto-optic spectrometer (AOS), auto-correlation spectrometer (ACS) and the filterbank spectrometer (FBS). Spectrometers based on all types of technology, except the autocorrelation type, must be designed with fixed bandwidth and resolution, i.e. they are inflexible for different kinds of observations. The autocorrelation spectrometer is in this regard flexible, but can suffer from a comparably high power consumption when processing very wide bandwidths. To be able to process extremely wide bandwidth signals (1-4GHz), most spectrometers must use a prefiltering stage to reduce the wide signal band into several narrower subbands, thus using a hybrid technique. The bandwidth of the filters can be 1-1.5 GHz for the AOS and 0.2-1 GHz for the ACS. We report on the frst experimental demonstration of a radio frequency (RF) spectrum analyzer based on Spectral Hole Burning (SHB). The ultimate goal of this investigation is to devise a RF spectrometer with a bandwidth in excess of 10 GHz and more than 1000 simultaneous spectral channels. A single-unit bandwidth of this device would outdo that of AOS and ACS by a factor better than 10. As an optoelectronic system, the SHB spectrometer would feature consumption requirements similar to those of the AOS. It would exhibit the additional benefit of resolution and bandwidth flexibility.Efforts to promote SHB technology were focused for a long time on large capacity data storage applications, thus masking the spectral specificity of the SHE3 process. Confronted with dominant conventional storage techniques, these efforts proved unsuccessful. Th'e SHB technology is more likely to emerge in the field of Fig. 1: overall beam arrangement, with the spectrometer principle in the insert. The modulator (M) transfers the RF signal (S(t)) on the monochromatic carrier delivered by the laser (DL). The carrier frequency v combines with the RF components at frequency in the two side bands. Each component at frequency v+b is diffracted in a specific direction by the gratings engraved in the SHB plate.The. SHB spectrometer concept relies on the engraving of monochromatic gratings in a ra...
