Radiometer for detecting and measuring low levels of pulsed laser sources

摘要

A radiometer the calibration of collimated pulsed laser sources. In one embodiment the laser sources have wavelengths of 1064 nm and 1540-1570 nm wavelengths at irradiance levels of 7×10−5 to 5×1010 Watts/cm2, with pulse widths of 5-400 ns. A lens system used to focus beams from the laser sources includes two piano convex lenses and one aspheric lens, all with 1.5 micron and 1.06 micron anti-reflection coatings. An InGaAs avalanche photodiode (APD) detector and a linear amplifier generate an output voltage which represents the pulse and power of the input laser. The output voltage is captured on a fast oscilloscope and converted to irradiance through NIST calibration factors. The detector is kept at a constant predetermined temperature with a heater ring and feedback circuit. The detector is mounted on a translation stage for placing the detector at the proper position for the 1064 nm and 1540-1570 nm wavelengths.