Optical Delay Modulator for Ultrafast Measurements
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
A technique is described whereby optical delay modulation is implemented in pumping or probing beam ultrafast measurement applications, so as to eliminate undesirable side effects of conventional beam chopping. Also discussed is a retro-reflector used to stabilize the angles of reflection. The delay modulation technique is compatible with standard lock-in techniques. In many optical ultrafast measurement applications, the standard method of increasing the signal-to-noise ratio is to chop the repetitively pulsed pumping beam at a fixed rate and to use a lock-in amplifier to detect changes in the probing beam, as the time delay between the pumping and probing pulses is varied. However, in some applications, chopping of the pumping beam produces undesirable false signals at the lock-in amplifier.