The idea of using laser interferometer for detecting gravitational waves was first proposed in 1962 (shortly after inventing lasers) by M. Gertsenshtein and V.

The idea of using laser interferometer for detecting gravitational waves was first proposed in 1962 (shortly after inventing lasers) by M. Gertsenshtein and V. Pustovoit [1]. So it took more than 50 years from the idea to its implementation. [1] http://www.jetp.ac.ru/cgi-bin/dn/r_043_0605.pdf http://www.jetp.ac.ru/cgi-bin/dn/r_043_0605.pdf (in Russian, Abstract in English at the end).