試題詳解

複選題
16. Assume two electromagnetic waves (frequency f_A and f_B) enters a nonlinear material whose polarization field includes a term that is proportional to the square of the clectric field. Which of the following frequencies could one possibly observe at the output of the nonlincar material?
(A) f_A+ f_B
(B) 2f_A
(C) 2f_B 
(D) All of the above.