Most CO2 laser power meters are very expensive and are equipped with capabilities far beyond what the common laser machine operator/owner needs. These instructions show a sub-$100 laser power meter probe at work, taking quick laser power measurements in less than a minute, with minimal setup time.
The Mahony laser power meter fits CO2 lasers and YAG lasers. It works with lasers that operate at 10.6 microns and 1.06 microns. At 1.06 microns it works for YAG, fiber, diode side pumped, and diode end pumped lasers and any additional laser technology operating at this wavelength.
Step 1: Put on Your Laser Safety Glasses With Side Shields.
Put on your laser safety glasses that are designed for the wavelength of your laser. Remember that a laser beam can easily be reflected so do not perform this test without safety glasses or goggles. Be careful not to permit the laser beam to reflect off of any of the stainless steel parts.
If you do not have laser safety glasses, then the LIA, or Laser Institute of America is an official body that has complete safety information available.
Step 2: Set the Pointer to the Zero Value
Set the dial face pointer to the zero value. It may not be at zero because the room temperature has changed. Use a screwdriver or wrench to adjust it. The adjustment is located on the back side of the stainless steel dial beside the word reset.
Step 3: Decide Where You Would Like to Take the Measurement - Example: Directly From the CO2 Laser
The photograph shows the laser power meter directly in front of the laser. Therefore, this test does not include the laser power measurement after the mirrors (which absorb a portion of the laser energy).
Depending upon your needs, you can decide where to take the measure. Several common needs for CO2 laser power measurements for laser engraving and cutting machines are listed below.
1. Measure laser output power for laser settings over time. Whether you own an RF (Radio Frequency) powered laser such as a Synrad or Coherent used in an Epilog brand or Universal Laser Systems brand laser engraving system, or if you own a Chinese high voltage glass tube laser, all gas lasers reduce power over time because of internal gas consumption. Therefore, your power settings for materials will change over time. By using the laser power probe you can measure results and set the same power everytime, no matter how your laser tube has degraded.
2. Spot check for bad optics. Sometimes, the optics go bad, and absorb much too much energy. So, even though the laser may be performing as usual, when you enter your laser settings on your laser engraving or laser cutting machine, the results are not as good as in previous jobs. By using the laser power probe before and after the mirror, you can measure the power loss, and if it is significant then change out the optic for a new one.
3. Measure maximum CO2 laser output power to certify purchased lasers perform per the warranty. Whether the laser is newly purchased, or near the end of its warranty period, the laser power meter probe is commonly used to measure laser output power. If the laser power is below the specified value, then you can do a warranty claim to have it replaced or receive a partial discount (as offered by some laser manufacturers).
4. To determine good beam alignment, a quick spot check on power in the four corners of the laser engraving and cutting table will let you know if losses are present and the laser machine needs aligning. This saves frustration in trying to guess why the laser is not performing as when first purchased.
Step 4: Decide Where You Would Like to Take the Measurement - Example: After All the Mirrors on a Laser Engraving Machine
To test if an optic is no longer functioning properly, place the probe in front of the optic to take a measurement. The subsequent measurement will be after the optic. When you calculate the power loss, then you will know if there is a problem with the mirror.
Step 5: Place the Black Body in the Path of the Unfocused Laser Beam
After you have decided the location for the laser measurement, then place the black body of the laser probe in the path of the unfocused laser beam. This can be done in the following manner:
Firmly hold the laser power probe by the dial. Place the black absorbing block in front of the unfocused laser beam. Be sure that the unfocused laser beam does not hit the reflective stainless steel because this is a safety hazard.
Step 6: Turn on the Laser Beam for 15 Seconds.
Turn on the laser for 15 seconds. The time is important, so use a stop watch, or some laser machines have a timer that can be used. If the time is 16 seconds or 14 seconds it will impact the accuracy of the reading.
Step 7: After the Laser Is Turned Off, Wait for the Dial to Hit It Maximum or Peak Value
After the laser is turned off, the pointer on the dial will continue to move. At the point it stops, note the measurement. This measurement value is the laser output power at the location of measurement.
The pointer will dwell at the maximum or peak value for ten seconds or more, before decreasing in value.
Step 8: For More Than One Reading, Cool the Black Body Back to Room Temperature
For more than one reading, such as when testing if a mirror has gone bad, cool the black body back to room temperature. This is typically done in one of two ways. One method is to wait for the pointer on the dial to return to zero. The second is to use a container of water to cool the probe more quickly.
This concludes the simple method to take laser power readings using a simplified, low cost device.
CO2 Laser power meter probes can be found for sale online, such as Amazon.com.