Dear Shaban,

         You can prefer over one of the Ph.D. subjects of physics

-Astronomy

-Quantum mechanics

-Atomic

-Electronics

-Optical instrumentation

-Photonics

-Molecular Biophysics

-Plasma physics

-Nuclear physics

and there are many other Ph.D. degrees in physics. Choose one on your interest.

Pursue it in a well-reputed university or

join MSc in the IITs or IISER, clear GATE, then join Ph.D. 

Go for research.

All the best.....!!!