This is my "NanoMeter Receiver".  It consists of an IR passing objective lens, and a photodiode mounted inside a PVC pipe cap which is fastened to the rear of the lens assembly by using aluminum tape.  The leads from the photodiode enter the metal MiniBox attached to the back of the pipe cap with four sheet metal  screws.  The box contains several terminating resistors for the photodiode, and a switch to select the proper resistor, depending on the intensity of the light source being observed.  A BNC coaxial cable connector is visible below the box.  A coax cable connects the detector unit to an oscilloscope for measurements.  The optical system formed by the objective lens and the attached lens on the photodiode package forms a 20X telescope. This allows for inspection of any particular section of the Rife/Bare tube as small as 2" in diameter while keeping the detector unit at least 6 feet away from the tube.  This eliminates RF interference problems, and furnishes excellent rejection of potentially interfering light sources.