抄録
We investigated the relationships of the sensitivity of laser microphones to the oscillation mode of LDs
using two types of them. A VCSEL has a side mode power ratio that ranges from 12 to 66 %, and for
DFB-LD the side mode power ratio that is less than 5 %. The sensitivity is affected by the side modes
and decrease more greatly with an increase of the side mode power ratio. When it exceeds 50%, the
sensitivity of the laser microphone decreases greatly. Although the sensitivity of a laser microphone
using VCSEL is 1.87 mV/Pa at most, the one using DFB-LD is 2.12 mV/Pa. We conclude that, the side
oscillation mode negatively affects to the sensitivity, which increases with an LD that has a lower side
mode and higher laser power. Therefore, DFB-LD is suitable for laser microphones.
