How to judge by sound whether the laser's frequency is appropriate

Many laser technicians use the practical technique of judging whether a laser is operating at the proper frequency by the sound it makes.The article will introduce how to combine the characteristics of high-frequency noise and vibration sound effects with laser equipment adjustment techniques, so as to quickly determine whether the frequency is in an optimal state, helping users save on adjustment time and avoid equipment loss.

Why can the sound reflect the laser frequency state?

You might not know that the sound emitted by a laser when it is in operation contains important information. If the frequency is too high or too low, the optical elements or mechanical structures inside the equipment will produce abnormal vibrations or frictional sounds.For example, a high-pitched sound might indicate that the frequency has exceeded the safe limit, while a low-pitched hum might mean that the energy transmission is unstable.The experienced operators usually listen to the sound of the machine before making any adjustments. This is even more direct than looking at the numbers.

Preparations: All of the above are needed.

If you want to make an accurate judgment about a sound, first you have to make sure you hear it clearly.

A quiet testing environment.

Find a room with as little background noise as possible, and turn off air conditioners and fans.If conditions allow, you can even wear ear muffs to block out the noise.

Auxiliary testing tools.

Prepare a sound recording program or a decibel meter for your cell phone. Record sounds that are hard to identify and listen to them repeatedly.Some experienced workers will even use a screwdriver to press against the equipment and listen to the sound transmitted through it. This method is especially useful for judging mechanical vibration.

Three steps to hearing the frequency.

Step 1: Remember what normal sounds like.

When the equipment is running normally, first listen to it carefully for one to two minutes.In good health, a laser will make a steady, uniform hissing sound similar to the noise a teapot makes when it first starts to boil, but quieter.

Step 2: Capture the characteristics of the abnormal sound.

• High frequency squeal: This is a sound like fingernails scratching a blackboard and may be due to overloading the resonant cavity with too high a frequency.

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• A dull humming sound: This may indicate inadequate cooling or a low frequency setting.

Step three: Adjust and listen to verify the effects.

Adjust the frequency parameter by 0.5 % and listen carefully to the change in sound.When the sound gradually weakens and returns to a steady rhythm, the frequency is close to the right one.When the readings on the instruments are checked again at this time, they are usually within ± 0.3 % of the set point.

These are the pitfalls that newcomers are most likely to fall into.

Don't be in a rush to adjust the parameters at the first sign of interference. First, rule out these common sources: 1.

• Dust accumulation on the cooling fan (try taking it apart and cleaning it).

• The platform screws are loose (use a wrench to tighten them).

Unstable voltage (a voltage stabilizer can solve this problem).

When should you trust the instrument over the ear?

Although listening to the sound to determine the frequency is very practical, there are two situations in which professional equipment must be used to test for it.

1. A high-precision scene requiring accuracy to the third decimal place.

2. When handling invisible laser light, such as infrared or ultraviolet, which may not even be audible.

Remember, the sound judgment method is best for quick, everyday adjustments. If you want to be more precise, you still have to rely on scientific data.