Control of the responsivity and the detectivity of superconductive edge-transition YBa2Cu3O7-x bolometers through substrate properties

The detectivity D* limits of YBa2Cu3O7-x bolometer on 0.05-cm-thick crystal line substrates are investigated, and a method to increase D* to greater th an 10(9) (cm Hz(1/2))/W at a 20-mu m wavelength is proposed. Because the re sponse increases proportionally with the bias current I-b, whereas the nois e near T-c (the transition or critical temperature) of our MgO and SrTiO3 s ubstrate samples does not, an increase in D* of these samples is obtained b y an increase in I-b. Another limiting factor is the de thermal conductance G(0) of the device, which, although controlled by the substrate-holder the rmal boundary resistance for our samples, can be changed by means of thinni ng the substrate to increase D*. The optimal amount of thinning depends on the substrate's thermal parameters and the radiation modulation frequency. D* in our samples is also found to follow the spectral-radiation absorption of the substrate material. (C) 1999 Optical Society of America.