PD300-MS | Laser Photodiode Sensors | Power Sensors - Ophir



The PD300-MS is a Microscope Slide power sensor that measures optical power at the sample plane of a microscope. The silicon photodiode measures from 350nm to 1100nm at optical powers ranging from 3µW to 1W and is designed to be a microscopy power sensor that answers the needs of fluorescence excitation measurements. The thin power sensor has a footprint of 76.0 mm x 25.2 mm matching that of a standard microscope slide. The sensing area is sealed and cleanable, allowing it to easily measure the output of high NA objectives that use immersion medium such as water / oil / glycerol as well as in air. The PD300-MS microscope slide power meter comes with a 1.5 meter cable for connecting to a meter or PC interface.


  • 18x18mm
  • 350-1100nm
  • 3µW-1W
  • 76 L x 25 W x 2.5 D (mm)
  • N.A
  • 20W/cm²
  • 0.2 s
  • 1W
  • CE, UKCA, China RoHS
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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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How can I measure light coming out of an oil immersion objective?

This is easy with the PD300-MS all you need to do is place a drop of oil on the center of the sensor surface and immerse the objective lens in it. After measurement just wipe down the sensor and clean it for another use.

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The area of the sensor is large, can I measure light at any point on it?

The sensor is large in order to 'catch' light coming out of the objective at large angles, it is most accurate when the light is centered on the surface – you should use the target on the backside of the sensor to position the sensor optimally.

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PD300-MS Microscope Slide Power Meter PD300-MS Microscope Slide Power Meter
Photodiode Sensors for Measuring Very Low Powers Photodiode Sensors for Measuring Very Low Powers Photodiode Sensors for Measuring Very Low Powers

In this short "Basics" video, we review in general the use of photodiode sensors for measuring very low laser powers.

Experiments using fluorescence microscopy? Ophir’s new PD300-MS Microscope Slide Power Meter lets you accurately measure the exact amount of light applied to a specimen, so experimental results across different equipment can be…objectively compared. The PD300-MS has the footprint of a standard microscope slide, and goes right in the object plane of your microscope.


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 Photodiode Sensor Damage or Out of Tolerance Conditions

We have included this document with your recent calibration order because we have noticed an out of tolerance condition obtained from your equipment when returned for calibration. This document was created to assist our valued customers in the proper care and maintenance of Ophir photodiode 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.

Ophir photodiode sensors can be used for many years without any repairs when used with the proper laser optical setup. Many of our customers have sensors that are using their original absorber that are over ten years of age. We hope that this document will enable you to also enjoy the long life and reliable results that Ophir- Spiricon is known for.


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


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.


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...

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...