Sf. Lee et al., VOLTAGE-BIASED SUPERCONDUCTING TRANSITION-EDGE BOLOMETER WITH STRONG ELECTROTHERMAL FEEDBACK OPERATED AT 370 MK, Applied optics, 37(16), 1998, pp. 3391-3397
We present an experimental study of a composite voltage-biased superco
nducting bolometer (VSB). The tested VSB consists of a Ti-film superco
nducting thermometer (T-c similar to 375 mK) on a Si substrate suspend
ed by NbTi superconducting leads. A resistor attached to the substrate
provides calibrated heat input into the bolometer. The current throug
h the bolometer is measured with a superconducting quantum interferenc
e device ammeter. Strong negative electrothermal feedback fixes the bo
lometer temperature at T, and reduces the measured response time from
2.6 s to 13 ms. As predicted, the measured current responsivity of the
bolometer is equal to the inverse of the bias voltage. A noise equiva
lent power of 5 x 10(-17) W/root Hz was measured for a thermal conduct
ance G similar to 4.7 x 10(-10) W/K, which is consistent with the expe
cted thermal noise. Excess noise was observed for bias conditions for
which the electrothermal feedback strength was close to maximum. (C) 1
998 Optical Society of America.