The attractive source of IR coherent radiation based on СО2-laser and frequency converters with Tl3AsSe3 monocrystals is proposed. The source is capable of covering spectral region 2 to 17mm and operating at room temperature. The second harmonic generator was experimentally investigated. The phase matching angle and its angular and temperature widths are 18°, 1.8° and 6° respectively. The doubling efficiency exceeded 2% for a 4,65 mm long crystal.