  Optical power measurements are needed in practically all technologies based
on light. Here we report a general-purpose optical power detector based on the
photoacoustic effect. Optical power incident on the detector's black absorber
produces an acoustic signal, which is further converted into an electrical
signal using a silicon-cantilever pressure transducer. We demonstrate an
exceptionally large spectral coverage from ultraviolet to far infrared, with
the possibility for further extension to the terahertz region. The linear
dynamic range of the detector reaches 80 dB, ranging from a noise-equivalent
power of 6 nW to 600 mW.
