Hello Verghese, MSc Photonics is a very promising branch in physics, but if you really want to pursue career as a researcher, scientist or university professor in this field, you have to pursue a PhD after your MSc.

But according to me CUSAT doesnt offer specialisation in Photonics , but it offers Nanostructured electronics of which photonics is part. 

If you want direct placement after MSc, you will have to settle for Tech and IT companies that visit the campus.

your future Prospects are:

• PhD leading to future research and univeristy positions and prospects
• DRDO, ISRO, or any other PSUs after Gate (PhD is preferred at ISRO and DRDO too)
• Bank PO, SSC, UPSC if you no longer want to continue in Physics
• School teacher after TET exams (and or B.Ed) 
• Campus placements in companies like TCS, VAROC, HELLA etc