Diode-pumped miniature ring lasers1,2 are known as reliable sources of stable single-frequency radiation. Due to their low amplitude noise and high inherent frequency stability they are well suited for high resolution spectroscopy and interferometer-based metrology. An especially high resolution is required for the detection of gravitational waves using Michelson type interferometers. For these systems, a light source with high continuous wave output power in single-frequency operation, excellent frequency stability and extremely low amplitude noise as close to the quantum noise limit as possible is essential. Based on a miniature Nd:YAG ring laser,2 a light source has been developed that has the potential to meet these requirements.3 By injection locking a high power diode-pumped rod laser to a miniature ring laser, a singlefrequency output power of 18 W has been demonstrated. Since the locking range scales with the power ratio of master and slave laser, a high output power of the master laser is desirable for reliable performance. This contribution reports on the substantial progress in power scaling of miniature ring lasers.