Systems, methods, and devices of the various embodiments may provide a fast and precise methods for continuously monitoring and measuring the absolute wavelength of monochromatic radiation sources, such as lasers, etc., irrespective of the temporal profile of the source (i.e., continuous wave, modulated, or pulsed). Radiation power measurement may also be enabled by the various embodiment methods. The various embodiment methods may utilize high-speed low-noise detection to enable fast and accurate measurements. High-precision wavelength and power measurement may be achieved in the various embodiments to monitor radiation source jitters and fluctuations, without relying on frequency transforms or dispersive optics. Both wavelength and power may be measured simultaneously or sequentially in various embodiments.