| 摘要 |
PURPOSE:To facilitate observing differential efficiencies (etaf, etam) and a threshold current Ith with a high accuracy and monitor the aging variation of a semiconductor laser output device with a high accuracy and in a short time by a method wherein a modulation signal whose current value is known is superposed on a driving current and the modulation output characteristics and the modulation signal are observed. CONSTITUTION:The amplitude DELTAPf of the light output Pf of a light output end is measured and a light output end differential efficiency etaf can be calculated from the amplitude DELTAi of a known modulation signal (i) by a formula etaf=DELTAPf/DELTAi. The amplitude DELTAIm of the monitoring current Im of a monitor output end is measured and a monitor output end differential efficiency etam can be calculated from the amplitude DELTAi by a formula etam=DELTAIm/DELTAi. Further, a threshold current Ith can be calculated by a formula Ith=IB-Pfo/etaf (wherein Pfo denotes a light output when the current is IB). Then the required monitoring is performed in accordance with the calculated results. |
