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Laser Diodes: Astigmatism (As) and Precautions for Using LD

The apparent focal position of the laser diode junction is different in the vertical direction and the horizontal direction. The distance between these two foci is defined as astigmatic difference (As).

What is Astigmatism (As)?

The apparent focal position of the laser diode junction is different in the vertical direction and the horizontal direction. The distance between these two foci is defined as astigmatic difference (As).

Laser Diodes: Astigmatism (As) and Precautions for Using LD

Astigmatism (As): Measurement Method

Astigmatism through[图1]Knife edge measurement shown.

The beam of the semiconductor laser is cut off from one side with a knife edge.

Laser Diodes: Astigmatism (As) and Precautions for Using LD
[图1]

The integral value of the laser beam can be obtained by plotting the amount of light passing through the edge and the position (X) of the edge.[图2]

Laser Diodes: Astigmatism (As) and Precautions for Using LD
[图2]

By differentiating it, the beam diameter (full angle at half value) can be measured.[图3]

Laser Diodes: Astigmatism (As) and Precautions for Using LD
[图3]

Move the end face position (Z) of the semiconductor laser to measure the beam diameter.

Plot the beam diameter and end face position in each direction perpendicular to the bonding direction of the semiconductor laser and horizontal.[图4]

The astigmatic difference can be obtained from the position of the minimum value of the two beam diameters.

Laser Diodes: Astigmatism (As) and Precautions for Using LD
[图4]

LD usage precautions

1) Since the ESD level is very low compared to other discrete products, if a surge is added to the forward direction, excessive light will be emitted, the end face will be damaged, and the laser will not be able to oscillate.

Laser Diodes: Astigmatism (As) and Precautions for Using LD

ESD: Abbreviation for Electro Static Discharge, which means electrostatic discharge.

2) When using, please do not touch the end surface that functions as a lens.

(Other discrete products can often use the end face as a “cutting allowance”.)

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