ANALISA POINTING STABILITY SINAR LASER MENGGUNAKAN QUADRANT PHOTODIODE (QPD)

Abstract

Measurement of pointing stability level of some laser beams has been conducted. The measurement system consists of two different laser types, QPD, QPD amplifier circuit, digital oscilloscope, CCD Camera and image processing software. There ware two measurement quantities that were observed, the stability of beam position on QPD, and the stability of beam size on CCD camera. QPD output was amplifield by QPD amplifield circuit then displayed on digital oscilloscope. The laser beam was pointed to CCD camera. There were three lasers used, one is He-Ne laser 638 nm in wavelenght, two diode laser with 650 nm wavelenght but diffrent in brand. The results showed that the position of beam on QPD representated by frequency fluctuation on the QPD output and the beam size on the CCD camera changed over time. The average position displacement of the Aixiz laser was 0.0048 Hz and it’s diameter displacement was 0.062 mm. Average position displacement of the Roithner’s laser was 0.0016 Hz and it’s diameter displacement was 0.15 mm and He-Ne’s laser, average positon displacement was 0.003 Hz and it’s diameter displacement was 0.288 mm. The value of displacement level of position and diameter of a laser indicated their pointing stability level. So the He-Ne laser unsstable in position stability while Aixiz laser was more stable in diameter . It could be because it’s size bigger than other