The «MARTIN-PUPLETT» is a spectrometer dedicated to THz studies that has been developed at the Néel Institute by the HELFA team (to characterize optical components dedicated to astrophysics studies). The encompass energy ranges from 2 to 100 cm-1 which correspond to  0.2 to 12 meV.

A 3He/4He dilution refrigerator is under construction. Both the detectors and the sample will be enclosed within the cryostat. The detectors will be cooled at 100 mK. The temperature of the sample will be varied from 1K to 50K.



The detectors will be Matrices of Kinetic Inductance Detectors (MKID) [Day et al, Nature 425, 817 (2003)]. Those detectors are RLC resonator circuits with meanders of superconductors which inductance varies owing the incident photons. The low frequency limitation is given by twice the superconducting gap value because photons with lower energy do not affect the circuit while above this energy the photons break the Cooper pairs. The high frequency limitation of the MKID is linked to the heat that the circuit can handle/evacuate while being superconductor. Playing with different superconductor materials and the circuit design (to evacuate the heat) it is possible to play with the low and high limitation frequencies.

Preliminary tests on aluminum-MKID gave the following results. The figure bellow presents four interferogrammes. Each interferogramme corresponds to a 8mn-acquisition time. The last figure shows the spectra obtain by Fourier Transform of the interferogrammes : the aluminum-MKID are sensitive to photons between 100 and 300 GHz (i.e 3 to 10 cm-1). In reality the high frequency limitation is due to filters installed on the cryostat in front of the detectors. The ratio of the first and the last spectra indicates a measurement stability of 2% within the 100-300 GHz range.



  1.     STAKES

  2.     PRINCIPLE

  3.     THE VERTEX