The poetry device used here is metaphor.
Metaphor is a poetry device that is used in comparing two unlike things without using words like 'like' or 'as'.
The phrase 'a wave of emotion' is metaphorical because the emotion that is felt at that time is compared to that of a wave without including words such as 'like' or 'as'.
Therefore it is a metaphor.
Hope it is clear ^_^
