1. A method for early diagnosis of Alzheimer, comprising: a) transmitting femtosecond pulsed laser light through a fiber carrier; b) splitting the femtosecond pulsed laser light into a pump light beam and a reference light beam; c) inserting into the pump light optical path a MOEMS rapid scanning delay line to generate wide bandwidth and rapid controllable optical delays; d) inserting the output of the MOEMS rapid optical delay lines to an optical chopper for improving signal processing; e) Inserting the output of the chopper to a terahertz transmitter; and f) illuminating the eye-lens with pulses of terahertz waves.