Essential Tools: Laser Measurement & Laser Beam Analysis Basics

Laser power sensors measure the power or energy level of electrical signals laser beams in various applications.

There are different types of power sensors, each tailored to measure power in specific frequency ranges and power levels for different needs.

Let’s discuss the two types of power sensors Ophir offers – thermal sensors and photodiode sensors.

Use cases differ based on the power you need to measure.

Photodiode sensors are used for low powers from picowatts up to hundreds of milliwatts, and as high as 3W depending on the model. Most of our photodiode sensors have a built-in filter that reduces the light level on the detector and allows for measurement up to 3W higher powers without saturation than would have been possible otherwise.

Thermal sensors are used for fractions of a milliwatt up to many thousands of watts, and can also measure single-shot energy at pulse rates not more than once every 5 seconds.

Ophir’s BeamTrack is an example of a thermal sensor, but in addition to measuring power it also measures beam power position and beam size. Together, This sensor provides you with a wealth of information on your laser beam, for example, centering, position and wander, size, power and single shot energy.

If you have the need to measure repetitive pulses rates, pyroelectric energy sensors are for you. Pyroelectric sensors measure the energy per pulse of repetitively pulsed lasers up to 25,000Hz, and they are sensitive to low energies.

And - If a pyroelectric sensor can measure a given beam’s energy per pulse, it can also be used to measure its average power.

It’s important to note that pyroelectric sensors are less durable than thermal ones. We’d recommend that use pyroelectric sensors only when you need to measure the energy of each pulse.

As we previously discussed, pyroelectric sensors are largely used to measure lasers with repetitive pulse rates repetitively pulsed beams, where we want to catch every pulse.

They measure repetitive pulsed energies and average powers at pulse rates up to 25000 pulses per second, and pulse widths up to 20 milliseconds.

Pyroelectric sensors are somewhat less durable than thermal sensors; if you don’t need and we recommend that you don’t use them unless it is necessary to measure the energy energy of each pulse and measuring . If average power is sufficient, there isn’t a need to use a pyroelectric sensor. then a power sensor rather than an energy sensor would be the right choice.

How do these special sensors work?

They are made of pyroelectric crystals that generate an electric charge proportional to the heat absorbed from the laser pulse.

The total charge generated is collected and the voltage difference is measured.

Once the energy is read by the electronic circuit, the charge on the crystal is discharged and it’s geared up to handle the next pulse.

Ophir’s pyroelectric detectors have unique circuitry that allow them to measure long pulses as well as short pulses, even when the pulse width is as much as 30% of the total cycle time.

Our new compact C line of pyroelectric sensors is a significant upgrade from earlier models.

They are more compact, they have a wider dynamic range, they have can handle higher pulse repetition rates and they can measure longer pulses.

Photodiode sensors are semiconductor devices that produce a current proportional to light intensity. These sensors have a high degree of linearity over a large range of light power levels - from fractions of a nanowatt to about 2 milliwatts.

Nearly all of Ophir’s photodiode sensors come with built-in filters that reduces the light level on the detector and allows measurement up to 30 milliwatts.

And most sensors have an additional removable filter allowing measurement to 300 milliwatts or 3 watts.

How do these sensors work?

When a laser photon source is directed at a photodiode detector, a current is created. The power meter unit amplifies this signal and indicates the power level received by the sensor.

Thanks to Ophir’s power meter circuitry, the noise level is very low.

And thanks to our exclusive patented dual detectors, the sensor automatically eliminates any signal that perhaps can illuminate detectors with subtracts background light.

And how accurate are these sensors?

The sensitivity of various photodiode sensors varies from one sensor to another but each one is calibrated in a two-stage process against a NIST photodiode calibration standard.

First the photodiode is calibrated with a monochromator over its entire spectral range.

And then, the calibration is tested using several lasers to “anchor” the results of the first stage, thereby ensureing the most accurate sensor readings.

A scanning slit profiler scans across a laser beam with a tiny slit, rather taking a picture of the entire beam at once. This process exposes details about the beam's shape, size, and how bright it is in different places.

Ophir’s NanoScan 2s slit profiler is the most versatile laser beam profiling instrument available today, providing instantaneous feedback of beam parameters for continuous waves CW and kilohertz pulsed lasers, with measurement update rates to 20Hz.

The natural attenuation provided by the slit allows the measurement of many beams with little or no additional attenuation. The high dynamic range makes it possible to measure beams while adjustments to focus are made without having to adjust the profiler.

Just aim the laser into the aperture and the system does the rest!

The NanoScan 2S is available with silicon, germanium or pyroelectric detectors to cover the light spectrum from UV to very far infrared.

And it’s available in a wide variety of apertures and slit sizes to allow for the accurate measurement of varying beam sizes.

To make it even more convenient and portable, the NanoScan 2s has direct USB connectivity. No external controllers or power supplies are required.

And a the rotation mount offers vertical operation if needed.

The profiler’s software comes in two versions, STD Standard and PRO Professional. The Professional version includes ActiveX automation for users who want to integrate into OEM systems or create their own user interface screens with C++, LabView, Excel or other OEM software packages.
Finally, the NanoScan 2s graphical user interface makes it easy for you to set the display screens to any configuration, so you can see only just the features you need.

Pyroelectric technology uses is used in cameras and arrays for laser beam diagnostics of nearly all IR and UV laser wavelengths, and and in high temperature thermal imaging.

Ophir’s core pyroelectric technology comes from begins with its specially designed sensor array, which has proven to be the most rugged, stable, and precise IR detector array available.

It’s these sensors that are embedded in Ophir’s Pyrocam line of cameras. They can operate at intensities 100 times greater than any other CCD camera, offering precision, stability, reliability, and versatility.

With the Pyrocam line, you get clear quantitative images displayed in 2D or 3D views. It’s the easiest way for you to instantly recognize whether your beam characteristics and what they tell you about affect your laser’s performance.

When and where can you use Pyrocam’s technology?

First, it’s an ideal measurement tool for scientific laboratory investigation of laser beams in physics, chemistry, and electronic system designs.

It’s also useful in assembly lines using CO2 and other infrared lasers. The system’s imaging instantly alerts you to detrimental laser variations and allows you to timely correct the problem and re-tune the laser parameters in a timely manner.

Pyrocam sensors are also used in some of the most sensitive medical applications, such as lasers for eye surgery and dermatological procedures where uniformity of the beam profile is crucial.

Pyrocams come bundled with Ophir’s BeamGage software, a state- of-the-art beam profiling system that performs rigorous data acquisition and analysis of beam size, shape, uniformity, divergence, mode content, and expected power distribution.

Simply connect the Pyrocam to your PC, run BeamGage software, and images are immediately displayed so you can make sure that your lasers remain accurate perform as they are supposed to all the time.

The BeamTrack is one a family of Ophir’s line of thermal sensors, which is capable of measuring beam position, size and power all at the same time all at the same time, and in a as well as single energy shot pulse energy.

How does it work?

The signal coming from the sensor’s aperture is divided into 4 quadrants.

Once divided, tThe output signals from these signals 4 quadrants are measured and compared, and the position of the beam centroid is calculated from this.In this way, position of the center of the beam is predicted with a very high degree of accuracy.

In addition to these 4 quadrants, special patented beam size detectors process the outputs and give you the measurements for beam size along with beam position.

What makes the BeamTrack different from other Ophir thermal sensors?

The BeamTrack sensors have a small electronics module situated on the cable from the sensor to the smart plug.

When the BeamTrack sensor is plugged into a compatible displays or PC interfaces meter or virtual meter, it offers a visual display of the beam position and beam size along with a readout of the power, making it very easy for you to log and track changes in the beam.