The share price of Emcore Corp. has fluctuated in recent weeks. The Alhambra-based semiconductor manufacturer for the aerospace and defense industries saw its share price decrease by 21% from its close of 52 cents on Dec. 12 – the day it released its fiscal fourth-quarter earnings – to a close of 41 cents the following day on almost 2.2 million shares traded, or its third-highest volume of the past year.