  We present a study of the response to pulsed infrared radiation of Fe-layer
shunted pnictide thin film microstructures. The thin film multilayer consisting
of 20 nm thick Fe-buffer, 50 nm thick Ba(Fe,Co)2As2 film and gold protection
layer were deposited on heated MgO and MgAl2O4 substrates by pulsed-laser
deposition. The multilayers were patterned into 5 to 8 um wide and 5 um long
microbridges by electron-beam lithography and ion-milling technique. The
microbridges show Tc up to 20 K and a critical current density up to 2.56
MA/cm2 at T = 10 K. The photo-response of Fe-shunted Ba(Fe,Co)2As2 thin film
microbridges to infrared radiation was studied in a wide range of incident
optical power, operation temperature and bias current. We have found that the
electron energy relaxation in studied multilayers is dependent on substrate
material and is 1.75 times faster in case of MgAl2O4 characterized by lattice
matching to pnictide film in comparison to MgO substrate.
