The 5000W-LP2-50 is a water cooled thermal power/energy laser measurement sensor for high power density and long pulse lasers. It has a 50mm aperture and can measure power from 20W to 5000W. Its high damage threshold LP2 coating covers the spectral range 0.35 - 2.2. The sensor comes with a standard 1.5 meter cable for connecting to a meter or PC interface.
- Ø146 W x 47D (mm)
- 3 s
I see Ophir has released some new thermal sensors with an absorber called “LP2”. What is it?
The new “LP2” type sensors are specially designed for beams having high power and high power density (and for pulsed beams, high energy density). The LP2 sensors are replacing the equivalent LP1 sensors; as impressive as the LP1 is, the LP2 was developed with the following improvements:
- Very high damage threshold, for both power density and energy density, for long pulse and CW beams;
- Spectrally flat; since its absorption remains constant at widely differing wavelengths, this means that sensors based on the LP2 can be used for "white light" or polychromatic beams;
- Very high level of absorption (as high as 96%, depending on wavelength), meaning much less light is scattered back, which for high power beams is an important benefit;
- The absorption is also largely independent of incident angle, which means it can be used for divergent beams too.
Do I need to recalibrate my instrument? How often must it be recalibrated?
Can a laser measurement depend on the distance from the laser to the sensor?
In theory, if a beam is completely parallel and fits within the aperture of a sensor, then it should make no difference at all what the distance is; it will be the same number of photons (ignoring absorption by the air, which is negligible except in the UV below 250nm). If, nevertheless, you do see such a distance dependence, there could be one of the following effects happening:
- If you are using a thermal type power sensor, you might actually be measuring heat from the laser itself; when very close to the laser, the thermal sensor might be “feeling” the laser’s own heat. That would not, however, continue to have an effect at more than a few cm distance unless the light source is weak and the heat source is strong.
- Beam geometry – The beam may not be parallel and may be diverging. Often, the lower intensity wings of the beam have greater divergence rate than the main portion of the beam. These may be missing the sensor's aperture as the distance increases. To check that you'd need to use a profiler, or perhaps a BeamTrack PPS (Power/Position/Size) sensor.
- If you are measuring pulse energies with a diffuser-based pyroelectric sensor: Some users find that when they start with the sensor right up close to the laser and move it away, the readings drop sharply (typically by some 6%) over the first few cm. This is likely caused by multiple reflections between the diffuser and the laser device, which at the closest distance might be causing an incorrectly high reading. You should back off from the source by at least some 5cm, more if the beam is not too divergent.
Needless to say, it’s also important to be sure to have a steady setup; a sensor held by hand could easily be moved around involuntarily, which could cause partial or complete missing of the sensor’s aperture at increasing distance, particularly for an invisible beam.Close
Is there a coolant pressure specification for Ophir water-cooled sensors?
Yes. Please reference the chart below:
Minimum Flow Rates for Water-Cooled Sensors
|Sensor||Recommended flow rate at full power1
|Minimum flow rate at full power1
|Absolute minimum flow rate
|pressure drop across sensor
(bar, at maximum flow rate)
|Pressure drop across sensor
Note: The coolant pressure should not exceed the minimum by more than 2.5 times.
What is the best water to use in the Water Cooled Sensors?
Corrosion is caused by interactions between the metallic components of the sensor and the cooling water, which may contain a variety of dissolved ions. Many factors affect the risk of corrosion forming, but the most important are the pH and the mixture of ions in the water. For this reason, we recommend using neutral deionized water in a closed circulating system (pH between 6 and 8). Please note that deionized water is usually slightly acidic (pH 5.65) due to absorption of CO2 from the atmosphere. The cooling water can be neutralized by adding 5 ml of a 10 mM solution of NaOH for each liter of water in the cooling system. Commercial additives such as Optishield Plus are also recommended for systems such as ours that have copper and aluminum in them. Optishield has the additional benefit of having biocide to prevent buildup of organic contamination.
To prevent corrosion it is also crucial to not allow standing water to evaporate inside the sensor when it is not in use. When disconnecting a sensor from the cooling system, the water channel should be cleared by blowing compressed air through it.
For those customers still experiencing problems with corrosion, we recommend the new thermal sensor 1000WP-BB-34 which has a special design in which all materials that come into contact with the cooling water are either copper or nonmetallic.Close
Once and for all: Is DI (deionized) water good or bad for water-cooled sensors? Does it help prevent corrosion, or does it actually increase the risk?
Many factors affect the risk of corrosion forming, but the two most important are:
- the mixture of ions in the water
- the water’s pH
Our current recommendation is to use DI water – but of a neutral pH. DI water is usually slightly acidic; it can be titrated to a neutral pH, using a bit of sodium hydroxide for example. There are also commercial additives that can help prevent corrosion, for instance Optishield Plus. For a more detailed discussion, see the FAQ at http://www.ophiropt.com/laser--measurement/knowledge-center/faq/7805
The sensor I need uses water cooling. Can you recommend a water cooling system?
We don’t supply chillers, nor insist on specific models; the only important thing from our point of view is to simply keep to the requirements specified for the cooling water of the specific model of sensor, such as minimum flow rate at full power, water temperature range, and - more important than the actual water temperature - water temperature stability. The temperature of the water should not be changing by more than 1 deg/min (because changes in water temperature could cause heat flow in the sensor which would be detected as if it were laser power, and cause errors in the reading).
We also have a video on our site at http://www.ophiropt.com/laser-measurement-instruments/laser-power-energy-meters/knowledge-center/water-cooled-sensors-youtube, which discusses various issues and tips about water cooling. There is a short discussion of coolant pressure requirements in our FAQ section at http://www.ophiropt.com/laser--measurement/knowledge-center/faq/2404Close
In this video, you will learn about some critical issues you need to consider when using water cooling, such as water temperature, water flow rate, and corrosion prevention.
Even higher damage threshold…flat spectral response…absorption up to 96%...
These are some of the characteristics of the new “LP2” type laser power sensors from Ophir.
Learn more in this video.
How to use water cooled Ophir sensors
Protective Housing with shutter for Ophir 5000W, 10K-W and 15K-W sensors
Metric water fittings for all water cooled sensors except 30K-W with quick connection to 10mm plastic tubing. Replaces standard fitting connecting to 3/8" tubing
Protective Cover with Target Pattern for 1000W, L1500W, 5000W, 10K-W and 15K-W sensors (1 unit supplied with 5000W, 10K-W, and 15K-W)
3m cable to connect sensor to power meter or interface. Order along with sensor to receive this instead of the standard 1.5m cable.
5m cable to connect sensor to power meter or interface. Order along with sensor to receive this instead of the standard 1.5m cable.
10m cable to connect sensor to power meter or interface. Order along with sensor to receive this instead of the standard 1.5m cable.
12m cable to connect sensor to power meter or interface. Order along with sensor to receive this instead of the standard 1.5m cable.
Allows connection of smart sensors to voltage measuring device for measurement of raw voltage output