A line of mid- and far-IR long-pass filters based on porous silicon technology has been introduced by Lake Shore Cryotronics Inc. The company says that the patent-pending all-silicon design has good thermal and mechanical properties, even at cryogenic and elevated temperatures, and will not delaminate under harsh conditions. Wide and flat spectral response is above 200 µm, with cut-on wavelengths from 4 to 100 µm. Diameters from 0.5 to 4 in. are available, as are standard and custom designs. Applications include Fourier transform infrared spectroscopy, astronomy and IR detector research.