Creating stable gravitational waves requires a tremendous amount of energy and extremely precise instrumentation. Currently, the most successful method for detecting gravitational waves is using interferometric detectors like the Laser Interferometer Gravitational-Wave Observatory (LIGO). These detectors employ high-energy particles, specifically lasers, to measure the minuscule distortions caused by passing gravitational waves.
While using lasers or microwave frequencies as an energy source may seem appealing, they are not suitable for directly generating gravitational waves. Gravitational waves are produced by the acceleration or oscillation of massive objects, such as black holes or neutron stars. The energy involved in creating gravitational waves is immense, and it requires the interaction of massive bodies undergoing extreme conditions or events.
In the case of LIGO's detectors, the lasers are used to measure the changes in distance caused by gravitational waves. The interference pattern of the laser beams is carefully analyzed to detect these minute fluctuations. Microwaves or other frequency sources do not possess the necessary characteristics to directly generate or detect gravitational waves.
To generate gravitational waves, you would need astronomical events or extreme astrophysical systems, such as binary neutron star mergers or black hole collisions. These events involve the acceleration of massive objects and generate ripples in the fabric of spacetime, which propagate as gravitational waves.
In summary, stable gravitational waves require the interaction of massive objects undergoing significant accelerations or violent events. Lasers and microwave frequencies, while useful for measurement and detection in interferometric detectors like LIGO, are not suitable for directly generating gravitational waves.