J.B. Electronics designed the first LaserBee™ LPM product back in 2007 under BAUER Electronics Inc.
Since then we have continually improved our products to be as accurate as possible by investing in new commercial and professional grade NIST traceable Laser Power Meters and additional laboratory electronic test equipment to calibrate and assure an as accurate as possible LaserBee™ LPM product. Since our first LaserBee™ LPM debut we have also added numerous new LaserBee™ LPM products and features to meet the changing needs of the hobbyist's Laser Power Meter market in the past years.
We have recently found to our dismay that some hobbyist LPM competitor's specifications of power density seem to have been calculated or tested incorrectly or their rating claim was in error. Needless to say their Power Density claim is definitely quite misleading. How can a laser hobbyist technician know what the real power density of a specific Laser Power Meter or Sensor actually is ?
We rely on the honesty and integrity of the seller.
WHAT IS POWER DENSITY ???
When you stand out in the Sun for a short time you can feel the heat of the sun and the heat does not really burn or char your skin.
On the other hand if you take a Magnifying Glass and capture only the rays falling on the magnifying glass's diameter and focus the same Sun to a pinpoint you will definitely burn and possibly char your skin. That is due to a higher power density when the sun is focused onto a smaller area. This is true for any light source.
Pertaining to Laser Power Meter Sensors and their Coating... Maximum Power Density refers to how much laser power per area that can be applied to the Sensor's coating before you degrade or damage the sensor's coating.
Usually Laser Power Density is expressed in Watts per square Centimeter or W/cm2 .
For example if a sensor with a claimed maximum power density of 20W/cm2 is expressed we can find the amount of laser power that we can safely apply to this sensor before causing any damage to the sensor. In this example case if we have a laser with a beam that is 4mm in diameter the beam will cover 12.566 mm2.
At 20W/cm2 the power density per square millimeter would be 20000 / 100 = 200mW/mm2. Therefore your Laser with the 4mm diameter beam that you want to test can not be more powerful than 12.5 X 200 = 2500mW (rounded off safely) or you will damage the sensor's coating.
For the above example J.BAUER Electronics would specify a Minimum beam diameter of 4mm and a Maximum Laser Beam power of 2500mW or 2.5W. This is safe for that sensor if respected.
To find the safe maximum Power Density in W/cm2 of a LaserBee Thermopile Sensor's coating with the above power specs you can use this formula....
Max Rated power / Min area of Laser beam / 10 or (2500) / (12.5) = 200 / 100 = 20 W/cm2
J.BAUER Electronics has not used direct Power Density figures that require some calculations on the customer's part for our LaserBee™ LPM products. We instead state a Minimum acceptable diameter of Laser beam that can be used and at what Maximum Power Rating of the specific LaserBee™ product in question. This is much simpler and easier for the novice technician or customer to understand and use.
We test all our different Thermopile Sensor broadband coatings using the same established in-house procedure. We use a water cooled high power variable adjustable output power laser with a known and adjustable beam diameter in conjunction with our Lab quality LPMs and test our coatings to destruction.
Recently we did a test on a competitors "X4" Laser Power Meter rated at 3700mW only to find that when tested in similar proceedures we test our LaserBee USB 3.7W (3700mW) Sensors the competition's sensor smoked at ~1700mW and was damaged at ~1900mW yet was rated by the seller at 3700mW. This is less than 50% of the claimed max power of this product compared to a LaserBee™ product with same claimed power.
In a nutshell... Be careful of the stated and claimed max power of hobbyist's Laser Power Meters. Be sure to ask what the Minimum Laser beam diameter is for the stated Maximum Power claimed.