Complex sentence: Initially PLT was proposed to overcome the difficulties in injecting sufficient laser power in high-Q optical cavities, and it was assumed that the cavity would be very sensitive to the stability of the mirrors and other optical parameters as in the passive cavities.
Split into simpler sentences: Initially PLT was proposed to overcome the difficulties in injecting sufficient laser power in high-Q optical cavities. It was assumed that the cavity would be sensitive to the stability of the mirrors and other optical parameters as in passive cavities.