Radiant power measurement detector equipped with a compact size 16mm diameter integrating sphere for small size sources with divergent beam light emittance like laser diode dyes & optical fibers. The small footprint detector can be placed directly in front of the light source to collect the entire light beam through its 3mm measurement port. The standard detector is built with a silicon photodiode to measure over a spectral range from 400 to 1100nm. An alternative model with a FC connector added allows connection of a spectrometer. The FC connector is located opposite the measurement port to collect the maximum amount of light signal for high resolution spectrometers with limited sensitivity. The detector head is traceably calibrated and certified to international standards. The ISD-1.6-Si-1 and ISD-1.6-Si-FC-1 detector head can also be supplied in a near-infrared version with an InGaAs photodiode to cover the 800nm to 1700nm spectral range.