Please could you give us an introduction to gRAY product line?
For all processes carried out with a laser system, the laser power is the core parameter that needs to be monitored and controlled. With our gRAY detectors, we provide laser power detectors suited for OEM applications. They are thermopile-based detectors the wavelength range from UV to MIR can be measured accurately and fast.
The gRAY portfolio offers detectors for measuring powers as low as 10 uW but also up to 100W. Our main attention is the easy handling and integration into laser systems as well as the robustness of the detectors.
gRAY B01-SMC laser power detector from greenTEG
How does laser power measurement work?
The working principle of thermopile sensors is based on the so called Seebeck effect. In an absorption layer on the sensor surface, the incident radiation is transformed into heat energy. This heat causes a temperature difference between the upper and lower surface.
A series connection of thermocouples inside the sensor is arranged in such a way that the junctions are located alternating on the hot and the cold side. Due to the thermoelectric Seebeck effect, an electric voltage builds up, which is proportional to the incoming radiation power.
Thermopile sensors are therefore sensitive to radiation of all wavelengths, as long as the absorptive coating is efficient. Broad band absorbers are typically used and hence the spectrum from UV to MIR lies within the detection range.
What are the industry applications of the gRAY sensors?
Typical customers are manufacturers of industrial or medical laser systems as well as laser manufacturers. Due to safety and process stability reasons, power detectors are integrated. This can be at various positions, e.g. behind the back mirror of the laser cavity; behind a beam splitter, which couples out a small fraction of the main beam onto the detector; or in the main beam path for occasional measurements.
Since the sensors cover a large power and wavelength range, the applications vary from monitoring units in low power QCLs with emission wavelength of 2.63 um to 5 kW CO2 cutting laser systems.
What are you exhibiting at LASER World of PHOTONICS this year?
We will present our gRAY product line for OEM applications, which was launched earlier this year. The portfolio ranges from bare die detectors to fully integrated laser power heads.
Besides the standard products we will launch three new gRAY products. Based on our customer’s feedback and ideas for additional products, we developed these new detector modules: A very fast 100 W laser power head and two PCB integrated sensor modules for low powers.
What new capabilities do these models add to the gRAY line?
The new C100-HW is among the fastest laser power detectors on the market. Powers of up to 100 W can be measured with a rise time of only 200 ms in a wavelength range from UV to MIR.
With the B01-SMC and the B05-SMC, we address two common concerns of our customers:
- System integration: The detector is SMD soldered onto a metal core PCB ensuring optimal electrical, mechanical and thermal coupling to this base plate. The PCB can be conveniently mounted onto any heat sink inside the laser system with two screws.
- Temperature monitoring: All thermopile detectors have a temperature dependent output signal. Therefore, the B01-SMC and B05-SMC contain a NTC temperature sensor next to the detector on the PCB to monitor the module temperature continuously if required by the application.
gRAY B05-SMC laser power detector from greenTEG
How are those detectors unique in the world of laser power measurement?
Fast monitoring of the laser power allows to react quickly to any unwanted change in signal. Conventional thermopile detectors typically have rise times of more than 1 second. With the C100-HW we therefore offer a detector, which is more than 5 times faster and at the same time accurate and cost efficient.
With the gRAY bare die detectors, low powers down to 100 uW can be measured. The new B01-SMC and the B05-SMC represent detectors that facilitate the measurement of low laser powers by an extra T-sensor and a mounting plate. At the same time provide freedom to the customer regarding the electrical and mechanical integration.
How have you achieved the fast measurement speed of the C100-HW?
Such a low rise time is achieved by an axial thermopile arrangement combined with a minimized thermal mass. Both characteristics – a short heat path and low thermal capacitance – lead to fast thermal equilibration. Furthermore, the position and design of the thermoelectric junctions between the thermopiles in the device is tailored to optimize the transient behaviour.
How are these new sensors easier to integrate into OEM systems?
The C100-HW contains amplifier electronics inside the housing, and the output signal is a normalized analog voltage between 0 and 10 V, which can be readily processed inside the control unit of the laser system.
For the B01-SMC and B05-SMC the advantage lies in the simplified mounting. Commonly, measurements of low powers with a thermal sensor are challenging, since the thermal coupling to the heat sink needs to be carefully considered. By soldering the detectors onto metallic base plates, the heat transfer is optimized and the signal is more stable.
gRAY C100-HW laser power detector from greenTEG, housed with amplifier electronics and connections for water cooling
Why is the compactness of these new sensors an important feature?
Due to performance reasons, laser systems are designed to be as compact as possible. Hence, the monitoring unit is required to be space saving as well.
Usually, the detector is located outside the main beam path of a laser system and only a small fraction of the beam is coupled onto it. Especially when retrofitting a system a position off the beam path can be challenging to find if the detector is bulky.
Why have you chosen LWoP to launch the new gRAY sensors?
The LWoP is the most important trade show for the laser community at large. All our current and potential customers as well as our partners will be present there. We will therefore reach the community most efficiently and will hopefully get into many exciting face to face discussions about possible applications. This exchange with our business partners is very valuable for us and has resulted in product developments like the most recent ones.
How are you planning to further develop this product line in the future?
Fast and small photodiodes are often the detector of choice but are limited by wavelength and a maximum illumination power. To close this measurement gap, we are currently developing a new detector, which will be launched in July. With the B0.5-SC powers up to 500 mW can be detected on an area of only 2x2 mm2.
As all the other gRAY detectors, the B0.5-SC is sensitive from 190 nm to 15 µm. For easy integration the detector can be reflow soldered like a SMD component.
About Susanne Dröscher
Susanne has a background in materials science and physics. She received her PhD from ETH Zurich in 2012 and afterwards joined the greenTEG AG as a Sales Engineer. As Product Manager she is currently responsible for all photonics products.
At greenTEG she coordinates the development and customization of laser power detectors, which are adapted to the user’s requirements. These projects are carried out with close contact to the customers involving technical discussions and consulting.
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