Analysis of origin of measured 1/f noise in high-power semiconductor laser diodes far below threshold current

The 1/f noise is measured under the bias one tenth the threshold current of the InGaAs quantum well high-power semiconductor laser diodes (LDs). The noise origin is analyzed using the current and voltage 1/f noise and dynamic resistance characteristics. Then the relationship between the noise and the internal defect is analyzed according to the differences of LDs in the noise intensity and the fluctuation near the initial electrical derivative peak. The result shows that with currents 0.13 mA–1 mA, the dynamic resistance of the LDs is in the magnitude of hundreds of ohms, when the changing rates of both the noise intensity and the resistance reflect the typical features of the active region, while with currents 8 mA–32 mA, the dynamic resistance drops under 10 Ω and its changing rate slows down, when the 1/f noise intensity trend shows the features of the contact resistance. Moreover, the electrical derivative of LDs with weaker noise fluctuates milder and has more conspicuous initial peaks, while the electrical derivative of other LDs fluctuates acuter and hardly shows distinct initial peaks. The results indicate that the 1/f noise from the active region can be measured under bias currents far lower than the threshold currents of the LDs, and it can indicate the defects in the active region and further the reliability of the device.