and coming back to frequency question: I think this guy from another forum is mostly close to the subject, see below:

Typical power supply for a glass tube laser has two main basic control inputs.

1. TTL 5v signal that turns the laser on and off.

This can be done very rapidly. Example high speed engraving.

The AWC608 has a PPI feature. Whereby it turns the laser on an off while cutting, to produce a pulsed cutting action. Adjustable and called "Pulse Per Inch"

2. The milliamp output of the laser power supply is controlled in one of two ways:

A. 0 to 5V analogue signal. With 0v signal resulting in zero milliamp power supply output. And 5v resulting in maximum milliamp output. This method is usually used with a manually adjusted potentiometer. (Or Laser Power Dial)

B. PWM or "Pulse Width Modulation", sometimes called "Pulse Duration Modulation". Magnitude being the TTL voltage level (5v). Recommended frequency for my power supply is 20khz. The percentage of "on time" controls the power supply output. 0% resulting in zero milliamp output and 99% resulting in maximum milliamp output. This method is usually used by controllers like the AWC608 etc.

This PWM should not be confused with frequency as it relates to RF excited laser tubes as used in major US made lasers. And neither should PPI.

Usually the PWM signal is smoothed internally by the power supply, with a little circuitry, to reproduce the 0 to 5v analogue signal.

Varying the PWM frequency of a glass tube laser power supply should have no effect on the cutting characteristics. Moving too far away from the recommended frequency, will just destabilise the level of power modulation control, that the laser controller has over the laser power supply.

So if you are adjusting the PWM frequency in the belief that you are legitimately adjusting cutting characteristics, then IMO you are fooling yourself.

Again this is all about DC excited glass tube lasers. Not to be confused with ULS, Trotec, Epilog, etc.

Greolt