A new material, calcium-doped-yttrium iron garnet (Ca:YIG), which proves very promising in room-temperature thermistor bolometer applications, has been used to construct a continuous planar bridge structure which works as a thermistor bolometer detector (YIGTB). Experimental results concerning the electrical response of the bridge as a function of the position of the incident laser light beam are in perfect agreement with those predicted by computer simulation. Since the Ca:YIG has a relatively low thermal capacity and is highly adsorbing from the visible to the infra-red, YIGTB has proved highly responsive and faster than other commercial thermistors.