NOISE MEASURING DEVICE OF SEMICONDUCTOR LASER

摘要

PURPOSE:To measure the noise level of a semiconductor laser when high frequency is superimposed by a simple method, by obtaining difference in driving currents when DC current driving is performed and when the high frequency is superimposed at the same optical output. CONSTITUTION:A DC driving current (B) corresponding to a specified optical output of a semiconductor laser and a driving current (C) when a high frequency current is superimposed are noted. Then, the relationship between the difference between both values (B-C)/B and the noise intensity of the laser light at the optical output level when the high frequency is superimposed shows high correlation. The lower the difference, the lower the noise level. The semiconductor laser 10 is driven by a DC power source 11 and a high frequency power source 12. The power of the laser light is measured by a light detecting element 14, which is provided in front of the laser. The value of the DC driving current is measured by a voltmeter 13. The noise level can be evaluated by the measured value based on the presence or absence of the high frequency current at the same optical output.