On a normal AM transmission, you get upper and lower sidebands. So for a 1,000KHz transmitter AM modulated by a 1KHz tone you would get three outputs - the carrier at 1,000KHz, the upper sideband at 1,001KHz, and the lower sideband at 999KHz. The complete information is contained in either one of the two sidebands, the carrier and other sideband are only wasting power - so SSB (Single Side Band) transmissions only transmit one sideband, putting all the transmitter power into that (which gives the much greater range).
However, your IR beam isn't modulated in the same way, it's simply pulsed on and off - so you will get 'carrier' then 'no carrier', more like morse code than AM. Morse code is commonly known as CW, for Carrier Wave.