Injection Current-Light Output (I-L) Characteristics of Laser Diodes

If the gain (Gain) obtained by the amplification of the laser diode is higher than the internal loss and the loss of the magnetic mirror, oscillation occurs. That is, there is an oscillation current threshold.

What is the injection current-light output (IL) characteristic?

The graph below is the injection current-light output (IL) characteristic.

If the gain (Gain) obtained by the amplification of the laser diode is higher than the internal loss and the loss of the magnetic mirror, oscillation occurs. That is, there is an oscillation current threshold.

Maximum output is limited by kink (bending of the current-optical output line), COD (photo-destruction at the end), thermal saturation due to temperature, etc.

Injection Current-Light Output (I-L) Characteristics of Laser Diodes
Injection Current-Light Output (I-L) Characteristics of Laser Diodes

Injection Current-Light Output (IL) Characteristics: Measurement Methods

Use an optical power meter when measuring the optical output of a laser diode.

When setting the light-receiving surface, make all the laser beams incident on the light-receiving surface of the optical power meter.

Tilt the light-receiving surface by 5~20° relative to the optical axis to prevent the reflected light from the light-receiving surface of the optical power meter from returning to the laser diode.

The IL characteristic represents the relationship between forward current (IF) and optical output (PO), and the threshold current (Ith) and operating current (Iop) can be read.

The monitor current (Im) is the output current when the built-in photodiode monitors the laser light emitted from the back of the laser chip.

【Measurement diagram】

Injection Current-Light Output (I-L) Characteristics of Laser Diodes

Note:

Since these measurements are greatly affected by temperature, install a heat sink on the laser diode and use a temperature controller to measure while controlling the temperature of the case.

If the gain (Gain) obtained by the amplification of the laser diode is higher than the internal loss and the loss of the magnetic mirror, oscillation occurs. That is, there is an oscillation current threshold.

What is the injection current-light output (IL) characteristic?

The graph below is the injection current-light output (IL) characteristic.

If the gain (Gain) obtained by the amplification of the laser diode is higher than the internal loss and the loss of the magnetic mirror, oscillation occurs. That is, there is an oscillation current threshold.

Maximum output is limited by kink (bending of the current-optical output line), COD (photo-destruction at the end), thermal saturation due to temperature, etc.

Injection Current-Light Output (I-L) Characteristics of Laser Diodes
Injection Current-Light Output (I-L) Characteristics of Laser Diodes

Injection Current-Light Output (IL) Characteristics: Measurement Methods

Use an optical power meter when measuring the optical output of a laser diode.

When setting the light-receiving surface, make all the laser beams incident on the light-receiving surface of the optical power meter.

Tilt the light-receiving surface by 5~20° relative to the optical axis to prevent the reflected light from the light-receiving surface of the optical power meter from returning to the laser diode.

The IL characteristic represents the relationship between forward current (IF) and optical output (PO), and the threshold current (Ith) and operating current (Iop) can be read.

The monitor current (Im) is the output current when the built-in photodiode monitors the laser light emitted from the back of the laser chip.

【Measurement diagram】

Injection Current-Light Output (I-L) Characteristics of Laser Diodes

Note:

Since these measurements are greatly affected by temperature, install a heat sink on the laser diode and use a temperature controller to measure while controlling the temperature of the case.

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