# Sum-Frequency Generation Spectroscopy
Author: Dylan Clark
Date: 2020/5/7
# Heterodyne detection
Hetero， 古希腊语 héteros, 意思是 “other, another, different”， heterodyne detection 就是指外差测量. Heterosexuality 是指异性恋。
Homo, A clipping of words formed from Ancient Greek ὁμο- (homo-, “same”).
Homodyne Detection: measure the intensity of the signal field.
Heterodyne Detction: measure the magnitude and phase of the signal field.