100K-W | Laser Thermal Power Sensors | Power Sensors - Ophir



The 120K-W is a water cooled thermal power/energy laser measurement sensor for very high powers with a 200mm aperture. It has dimensions 520 x 545 x 750mm. The 120k-W laser power meter can measure power from 10,000W to 120,000W and is designed for a beam expanded to 100mm diameter to hit its deflecting cone and is calibrated at 1.07µm. Applications include laser weapon measurements and laser measurement for semiconductor lithography processes. The sensor comes with a 10 meter cable for connecting to a meter or PC interface


  • N.A.
  • Ø200mm
  • 0.9-1.1µm
  • 10kW - 120kW
  • N.A.
  • Less than 1%
  • 520 L x 545 W x 750 D (mm)
  • N.A.
  • N.A.
  • N.A.
  • N.A.
  • N.A.
  • N.A.
  • N.A.
  • CE, UKCA, China RoHS
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How should I clean my sensor?

First, clean the absorber surface with a tissue, using Umicore #2 Substrate Cleaner, acetone or methanol. Then dry the surface with another tissue. Please note that a few absorbers (Pyro-BB, 10K-W, 15K-W, 16K-W and 30K-W) cannot be cleaned with this method. Instead, simply blow off the dust with clean air or nitrogen. Don't touch these absorbers. Also, HE sensors (such as the 30(150)A-HE-17) should not be cleaned with acetone.
Note: These suggestions are made without guarantee. The cleaning process may result in scratching or staining of the surface in some cases and may also change the calibration.

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Must I use a particular sensor only with the meter it was ordered with?

Ophir meters and sensors are calibrated independently. Each meter has the same sensitivity as the other within about 2 tenths of a percent. Each sensor is calibrated independently of a particular meter with its calibration information contained in the DB15 plug. When the sensor is connected to the meter, the meter reads and interprets this information. Since the accuracy of our sensors is typically +/-3%, the extra 0.2% error that could come from plugging into a different meter is negligible and therefore it does not matter which calibrated meter we use with a particular calibrated sensor.

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When an accuracy spec is given, what exactly is meant?

The Ophir specification on accuracy is in general 2 sigma standard deviation. This means, for instance, that if we list the accuracy as +/-3%, this means that 95% of the sensors will be within this accuracy and 99% will be within +/-4%. For further information on accuracy see https://www.ophiropt.com/laser-measurement-instruments/laser-power-energy-meters/tutorial/calibration-procedure and https://www.ophiropt.com/laser--measurement/knowledge-center?search=calibration&=SEARCH

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How do you calculate the power and energy density of a laser beam?

If the power is P and the diameter of the beam is D then the power density is P /(.785 * D2) . If it is a pulsed laser and the energy is E, the repetition rate is R and the diameter is D then the power density is E*R/(.785 * D2), The energy density is E/(.785 * D2). The sensor finder will automatically calculate the power and energy density.

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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 (at maximum flow rate) pressure drop across 8 meter of tubing (at maximum flow rate)
liters/min) (liters/min) (liters/min) Bar MPa Bar MPa
L250W 3 3 3 0.3 0.03    
L300W 3 3 3 0.3 0.03    
1000W 6 3 3 0.3 0.03 0.5 0.05
L1500W 6 3.5 3 0.3 0.03 0.5 0.05
L2000W 6 3.5 3 0.6 0.06 0.5 0.05
5000W 8 5 3 0.6 0.06 0.5 0.05
6K-W-200x200 6 6 5 0.5 0.05 0.3 0.03
10K-W 8 8 3 1 0.1 0.5 0.05
15K-W 12 12 3 2 0.2 1 0.1
16K-W 12 12 3 1 0.1 0.8 0.08
30K-W 25 25 6 2 0.2 3 0.3
120K-W 60 60 30 4 0.4 3.5 0.035

You can find a lot more information about the correct use of water-cooled sensors in the article "How to use water cooled Ophir sensors", here.

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Does the damage threshold depend on power level?

The damage threshold of thermal sensors does depend on the power level and not only the power density because the sensor disc itself gets hotter at high powers. For instance, the damage threshold of the Ophir broadband coating may be 50KW/cm2 at 10 Watts but only 10KW/cm2 at 300W. The Ophir specifications for damage threshold are always given for the highest power of use of a particular sensor, something which is not done by most other manufacturers. This should be taken into account when comparing specifications. The Sensor Finder takes the power level into consideration when calculating damage threshold.

 Watch the 'FAQ: Does damage threshold depend on power level?' video

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Do I need to recalibrate my instrument? How often must it be recalibrated?

Unless otherwise indicated, Ophir sensors and meters should be recalibrated within 18 months after initial purchase, and then once a year after that.

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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.

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For the 120K-W sensor, what is the maximum power density? It is not given as such in the specification.

The spec was designed around the way such lasers are typically used. Since these lasers are normally used with focusing optics, the spec of the 120K-W does not give a maximum power density; rather, it defines the assumed focusing-lens focal length and position such that the beam will end up having a 100mm diameter at the cone, and defines the assumption of a near Gaussian beam under those conditions so we can define a baseline number. This is defined briefly in the spec, and in a bit more detail in the User Note that comes with the sensor.

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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 https://www.ophiropt.com/laser--measurement/knowledge-center/faq/7805


You can find a lot more information about the correct use of water-cooled sensors in the article "How to use water cooled Ophir sensors", here.

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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 https://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 https://www.ophiropt.com/laser--measurement/knowledge-center/faq/2404

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To help ensure correct alignment of my beam in my 120K-W sensor, can I insert the laser head (the QBH connector) into the opening of the 120K-W “beam dump” cylinder?

We would not recommend doing that. Besides possibly affecting the correct performance of the sensor, there is a risk of potential damage to the laser if a small percentage of the beam is reflected (off the sensor’s reflective cone) back into it.

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  • WaterFlowMeter PC Application

    Software: WaterFlowMeter PC Application
    Power measurement based on water temperature and flow rate

    Firmware: Firmware of sensor can be upgraded via WaterFlowMeter PC application.
    To download the firmware file go to: "Help/New Firmware" screen in WaterFlowMeter PC Application
    Note: When running the WaterFlowMeter PC Application, the Water Flow Meters (6K-W & 120K-W) are connected directly to the PC via supplied RS232 cable. If you want to use the Water Flow Meter with an Ophir power meter or with an Ophir interface with StarLab, the sensor operates as a standard thermal sensor measuring power only.


FAQ: Thermal Sensors for Measuring Low, Medium & High Laser Powers FAQ: Thermal Sensors for Measuring Low, Medium & High Laser Powers
FAQ: Sensors for Measuring Laser Power FAQ: Sensors for Measuring Laser Power FAQ: Sensors for Measuring Laser Power

In this short “Basics” video we review in general how one goes about measuring laser beam power, so that you’ll have a clear basic understanding of what the different sensor types are, and when you would use which type.

Measuring Very High Power Laser Beams: Challenges and Solutions Measuring Very High Power Laser Beams: Challenges and Solutions Measuring Very High Power Laser Beams: Challenges and Solutions

Laser beams with powers of many tens of kilowatts are becoming more and more common in today's applications. This video will discuss the technical challenges in measuring such lasers, and will show you a range of solutions now available

Water Cooled Sensors: Things to Look Out For Water Cooled Sensors: Things to Look Out For Water Cooled Sensors: Things to Look Out For

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.

In this short “Basics” video we review the use – and selection - of thermal sensors for measuring low, medium and high laser powers.



Tutorials and Articles

Laser Power Sensors introduction

As described in the general introduction, the thermopile sensor has a series of bimetallic junctions. A temperature difference between any two junctions causes a voltage to be formed between the two junctions. Since the junctions are in series and the «hot» junctions are always on the inner, hotter side, and the «cold» junctions are on the outer, cooler side, radial heat flow on the disc causes a voltage proportional to the power input. Laser power impinges on the center of the thermopile sensor disk (on the reverse side of the thermopile), flows radially and is cooled on the periphery. The array of thermocouples measures the temperature gradient, which is proportional to the incident or absorbed power. In principle, the reading is not dependent on the ambient temperature since only the temperature difference affects the voltage generated and the voltage difference depends only on the heat flow, not on the ambient temperature.


Common Reasons for Thermal Sensor Damage or Out of Tolerance Conditions

This document was created to assist our valued customers in the proper care and maintenance of Ophir thermal laser power sensors. The following information is for reference only. If you have any reason to believe that the sensor is no longer performing within the original specifications,we always recommend that you send it in for repair and/or recalibration by our trained technicians to bring the unit back to the proper NIST traceable standards. We believe that Ophir thermal sensors can be used for many years without any repairs when used with the proper laser optical setup. We hope that this document will enable you to also enjoy the long life and reliable results for which Ophir-Spiricon is known.


How to Properly Select a Laser Power or Energy Sensor

The selection of a sensor to accurately measure the power of a laser or energy of a pulsed laser can seem like a simple and easy procedure. However, many times the selection process is limited to choosing a sensor that only meets the range of power or energy to be measured, leaving out several other essential criteria of the laser specifications; that without their consideration, can allow the wrong sensor to be selected, the laser to be measured inaccurately and likely to cause the sensor to fail prematurely.

Watch Our Laser Measurement Video


Calibration Accuracy of Ophir’s High Power Sensors

An explanation of how we do this is provided below (A). In addition, a recent check of Ophir’s 5000W head by PTB in Germany shows excellent agreement between our calibration and their standards. The details of the correspondence between our sensor and their standard at powers up to 1400W is included here (B).

A. High Power Measurement Calibration Method and Estimated Accuracy of Models 5000W and 10K-W


How Much of the Power Sensor Aperture Can My Laser Fill Up?

The entire aperture senses power, so you can use the whole head. That said, a beam in the inner 50% of the surface area (about 70% of the diameter) is specified by Ophir to be uniform within +/-2%. The sensitivity around the edges might be a little less, but generally the sensitivity doesn’t vary by more than +/-2% over the entire aperture.


Effect of Ambient Conditions on Laser Measurements

We are often asked about the specified ranges of various ambient conditions (temperature, humidity, etc.) for Ophir instruments. In this article we will clarify the effects of these conditions on laser measurements, so you’ll be able to use your Ophir laser measurement instrument effectively.


How to Use Water Cooled Ophir Sensors

Ophir water cooled sensors are designed to measure high powers in a relatively compact package. In order for the sensor to operate properly, the water flow rate, temperature and temperature stability have to be in the right range. For best performance of the sensor, the water flow rate should be the recommended rate. If the user system is not able to reach the recommended rate, then the minimum rate can be used and the sensor will meet spec but there may be some degradation of response time and linearity... Read more...

Ophir Power/Energy Meter Calibration Procedure and Traceability/Error Analysis

This document discusses the interpretation and basis for stated measurement accuracy of Ophir Laser Power/Energy meters.
1. General Discussion
2. Combination of Errors and Total Error
3. Analysis of Power and Energy Calibration Errors
4. Detailed Analysis of Power and Energy Calibration Errors


Laser Measurements in Materials Processing: How and When They Absolutely, Positively Must Be Made

19th century British physicist and engineer William Thomson, 1st Baron Kelvin, was the first to say, “If you can’t measure it, you can’t improve it.” When applying this principle to improving laser-based processes, there are a variety of parameters that must be measured. Given the continuously rising power of laser systems in material processing, the requirements for measurement systems are more challenging than ever. Which technologies are available to measure high-power lasers? How often should they be measured? What measurements should be tracked? When this data is collected, what should be done with it? Read more...

How do I know what range, or scale, to set my power/energy meter to? And what happens if I go over range?

Each given range represents one level of gain of an internal amplifier. The electronics, as always, have a limited Dynamic Range. If the measured signal is too low, in other words near the bottom of the range, then it may be lost in the noise and the reading will be inaccurate and noisy. If it’s too high – there may be saturation issues. To give an instrument a usefully wide dynamic range, multiple scales or ranges are used. Switching from range to range can be automatic (“Autorange”), or manual. Autoranging simply starts automatically at the least sensitive range and works its way down the ranges, sampling the signal as it goes, till it finds a range at which the signal is properly detected. Note, by the way, that only in POWER mode is Autoranging available. If we are working in Single Shot Energy mode, there is no Autoranging – simply because when we are measuring a single pulse, the instrument has no opportunity to work its way down the ranges as in Power mode.


Types of power / Energy Laser Sensors General Introduction

Power and Single Shot Energy Sensors
Ophir provides two types of power sensors: Photodiode sensors and Thermal sensors. Photodiode sensors are used for low powers from picowatts up to hundreds of milliwatts and as high as 3W. Thermal sensors are for use from fractions of a milliwatt up to thousands of watts.
Thermal sensors can also measure single shot energy at pulse rates not exceeding one pulse every ~5s.

Repetitive Pulse Energy Sensors
For higher pulse rates, Ophir has pyroelectric energy sensors able to measure pulse rates up to tens of KHz. These are described in the energy sensor section, section 1.3.


5 Situations Where Laser Performance Measurement is Necessary

Measuring the performance of a laser has possible for a number of years and is accomplished with a variety of techniques. These electronic laser measurement solutions give the laser user more relevant, time-based data that shows trends in laser performance rather than single data points. While these solutions have provided laser users with the ability to present data in a simple and easy to understand manner, the application of the data still seems to be unclear to many laser users. Read more...


Customers that purchase the above items also consider the following items. Ophir-Spiricon meters and sensors include a standard manufacturers warranty for one year. Add a one year Extended Warranty to your meter or sensor, which includes one recalibration.
  • N Polarity Power Supply/Charger

    Power Supply/Charger for Centauri, Vega, Nova II, LaserStar, Nova, EA-1, Pulsar, Quasar, 6K-W, 120K-W and fan cooled sensors (1 unit supplied with these products)