Radiometers for Laser Radiation

Laser Power Meters, Radiometers, Dosimeters and Data Loggers for Irradiance, Laser Power, Laser Energy and Pulse Shape in the 400 nm - 1800 nm Wavelength Range.

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For the measurement of laser radiation different measurands are of interest. The most important is usually the total radiant power (see our application about laser power measurement). For this measurement either directly photodiode detectors, thermopiles/pyroelectric detectors or integrating spheres are used. Especially integrating sphere detectors are the ideal choice if the laser beams are divergent or in general of larger size. In any case a modern intuitive optometer (current amplifier with display) is needed in order to store calibration data of different laser wavelength or even different detectors. Please see our range of Optometers, Amplifiers and Display Meters for Laser Power.

Pyroelectric detectors are generally used to measure the energy of pulsed lasers with high-powers up into the kW range. However, these are less suitable for the low peak power and short pulse lengths of semiconductor lasers. Therefore, photodiodes are usually used.

For precise radiant power measurements a high sampling of the laser pulse is needed. Since these pulses are very often in the ns range a standard sampling of a transimpedance amplifier is not sufficient. A smart techniques to solve this challenge is to stretch the pulse by a multiple of the expected pulse length. This is called the pulse stretching method (P-21 Touch Screen Laser Power Meter or P-9710 Classic Laser Power Meter). The resulting ‘stretched pulse’ becomes flatter, but remains constant in its area, so constant in its radiant power. The stretched pulse can be sampled with an higher amount of sampling points.

Conversion of short pulses into stretched pulses with the same energy (area). A1: original signal input, A2: signal output transimpedance amplifier, Area A1 = area A2

The pulse waveform of the stretched pulse can be recorded in a time-resolved manner using a data logger with sufficiently high sampling rate. The pulse energy is thereby calculated from the pulse waveform. See our application page about laser power and waveform measurements.

We offer a range of Optometers suited for measuring the pulse energy of laser diodes using the pulse stretching method. Models P-21 and P-9710 have signal amplifiers with time constants which are designed ideally to the analog-to-digital converter with sufficient sampling time. Due to their high readout rate, electronic measurement uncertainty of less than ± 1% is possible with careful adjustment of electronic offsets.

These days additionally the pulse shape is of high interest due to very short pulses e.g. used in LiDAR applications. Laser diodes used for LiDAR distance measuring devices have furthermore very often a diverging elliptical beam profile with typical peak powers of up to 100 W or even in the kW range. They are operated in a short pulse width, low pulse frequency mode with low average power. The short pulses are of advantage in terms of the temporal resolution of the LiDAR system. For quality assurance, the peak power and the pulse waveform are of primary interest. These two optical parameters cannot be measured with a single detector if lowest measurement uncertainties are needed. Therefore, pulse energy and pulse waveform must each be measured separately, see e.g. our compact and well thought out ISD-1.6-SP-Vxx series and its larger size versions ISD-5P-SP and ISD-10P-SP.

The pulse waveform is measured using fast, small-area photodiodes terminated with a low-impedance shunt resistor. The temporal voltage curve across the resistor is measured and recorded with a digital oscilloscope. Rise times of less than a nanosecond are possible. The responsivity of this type of detector is very low because of the low-resistance circuitry.

Beside the design of the measurement system as well a traceable calibration with low calibration uncertainty is essential. We at Gigahertz-Optik offer ISO 17025 calibrations and testing according to DAkkS. Please see our ISO 17025 laboratory for traceable laser power meter calibrations.

Please see also our application examples in the laser power measurements section. In the product list below we present a selection of measurement solutions. Since we are experts in customized solutions in laser power measurements, the following customizations are of course possible:

adapt the laser radiation range (laser power range) to your needs
adapt the sphere diameter, sphere port size, etc. fitting to your device under test (DUT)
find the perfect suited calibration strategy, e.g. ISO 17025
finding the perfect suited optometer/display unit/transimpedance amplifier

Handheld/portable radiometers for measuring laser power, pulse energy, etc.

Model	Spectral function	Entrance optic	Entrance port	Typ. Range Minimum SNR=50 100ms integration	Measurement range Typ. Max.	Remark
P-21-4 + ISD-1.6-SP-Vxx	Si 400 - 1100 nm	16 mm Ø Integrating sphere	5 mm Ø	0.73 µW @630nm 0.66 µW @900nm	14.6 W @630nm 13.3 W @900nm	Two-photodiode technology for time-resolved measurement (ns) of the radiant power of pulsed laser diodes and LEDs. Optometer P-2120 or P-9710-4 for high dynamic range and precise pulse measurement mode. Optional oscilloscope for pulse shape.
P-21 + ISD-5P-SP	Si 400 - 1100 nm	50 mm Ø Integrating sphere	10 mm Ø		fast photodiode: typically 2000 W (@ 950 nm, pulsed)	Detector for the measurement of the temporal intensity course and the radiant power of pulse lasers and pulse LEDs. In conjunction with the optometers P-21, P-9710-2 and P-9710-4 and a fast oscilloscope, the absolute peak performance of pulse lasers and pulsed LEDs can be determined.
P-21 + ISD-10P-SP	Si 400 - 1100 nm	100 mm Ø Integrating sphere	20 mm Ø		fast photodiode: typically 7500 W (@ 950 nm, pulsed)	Compact measuring head with 100 mm diameter integrating sphere. Si photodiodes for radiant power and temporal intensity curve for pulse lengths in the ns range.
X1 + ISD-3P-Si	Si 400 - 1100 nm	30 mm Ø Integrating sphere	5 mm Ø	7.8 nW @630nm 5.6 nW @900nm	1.56 W @630nm 1.13 W @900nm	Integrating sphere detector with 30 mm ODM98 sphere for laser power measurements from 400 nm - 1100 nm. Suitable for CW-power as well as pulse energy measurements.
X1 + ISD-3P-IGA	InGaAs 800 -1800 nm	30 mm Ø Integrating sphere	5 mm Ø	0.29 µW @1300nm 0.25 µW @1550nm	5.9 W @1300nm 5.0 W @1550nm	Integrating sphere detector with 30 mm ODM98 sphere for laser power measurements from 800 nm - 1800 nm. Suitable for CW-power as well as pulse energy measurements.
X1 + ISD-5P-Si	Si 400 - 1100 nm	50 mm Ø Integrating sphere	10 mm Ø	2.0 nW @630nm	400 mW @630nm	Integrating sphere detector with 50 mm ODM98 sphere for laser power measurements from 400 nm - 1100 nm. Suitable for CW-power as well as pulse energy measurements.
X1 + ISD-5P-IGA	InGaAs 800 -1800 nm	50 mm Ø Integrating sphere	10 mm Ø	6.33E-10 W @ 1300 nm 5.85E-10 W @ 1550 nm	6.33 W @ 1300 nm 5.85 W @ 1550 nm	Integrating sphere detector with 50 mm ODM98 sphere for laser power measurements from 800 nm - 1800 nm. Suitable for CW-power as well as pulse energy measurements.
P-21-2 + ISD-5P-Si	Si 400 - 1100 nm	50 mm Ø Integrating sphere	10 mm Ø	2.0 nW @630nm	400 mW @630nm	Integrating sphere detector with 50 mm ODM98 sphere for laser power measurements from 400 nm - 1100 nm. Suitable for CW-power as well as pulse energy measurements. Optometer P-9710 with high dynamic range and precise pulse energy mode.
P-21 + ISD-5P-IGA	InGaAs 800 -1800 nm	50 mm Ø Integrating sphere	10 mm Ø	6.33E-10 W @ 1300 nm 5.85E-10 W @ 1550 nm	6.33 W @ 1300 nm 5.85 W @ 1550 nm	Integrating sphere detector with 50 mm ODM98 sphere for laser power measurements from 800 nm - 1800 nm. Suitable for CW-power as well as pulse energy measurements. Optometer P-9710 with high dynamic range.
P-21-1 + LP-9901	Si 400 - 1100 nm	Flat surface	7 mm Ø	3.9 nW @630nm 0.25 nW @900nm	0.77 W @630nm 50 mW @900nm	Laser power and laser scattered radiation. 7mm diameter measurement spot for laser safety measurements.
P-21-1 + PD-45 series	Si 350 - 1100 nm Ge 800 - 1800 nm TP 300 - 10000 nm	Flat surface	10 mm Ø			For laser diode measurement, VCSEL measurement, LiDAR laser measurement, tuneable laser power measurement, etc.
P-21-1 + PD-MSD series	PD-MSD-Si (200 nm - 100 nm) PD-MSD-TP (300 nm - 10000 nm)	76 mm x 25,2 mm x 5 mm	Fits directly into the focal plane of a microscope	PD-MSD-Si: 30 nW (typ) PD-MSD-TP: 100 µW (typ)	PD-MSD-Si: 30 mW (typ) PD-MSD-TP: 2 W (typ)	Laser power head for microscope measurements available in two versions (Si and Thermopile) for precise laser power measurement
MD-37 series + P-9710		Flat surface	Depends on Diode choice	Depends on Diode choice	Depends on Diode choice	Modular detector with differnet diode-options for laser power measurements. Wavelength range depending of selected diode. Suitable for CW-power as well as pulse energy measurements.
P-21 + ISD-10-Si	Si 400 - 1100 nm	100 mm Ø Integrating sphere	15 mm Ø	3.1 nW @630nm 2.6 nW @900nm	0.6 W @630nm 0.5 W @900nm	Integrating sphere detector with 100 mm barium sulfate sphere for laser power measurements from 400 nm - 1100 nm. Suitable for CW-power as well as pulse energy measurements. Optometer P-9710 with high dynamic range and precise pulse energy mode.
P-21 + ISD-15-Si	Si 400 - 1100 nm	150 mm Ø Integrating sphere	38.1 mm Ø	83 nW @630nm 71 nW @900nm	16 W @630nm 14 W @900nm	Integrating sphere detector with 150 mm barium sulfate sphere for laser power measurements from 400 nm - 1100 nm. Suitable for CW-power as well as pulse energy measurements. Optometer P-9710 with high dynamic range and precise pulse energy mode.
P-21 + ISD-30-Si	Si 400 -1100nm	300 mm Ø Integrating sphere	100 mm Ø	25nW @630nm 20nW @900nm	5 W @630nm 4 W @900nm	Integrating sphere detector with 300 mm barium sulfate sphere for laser power measurements from 400 nm - 1100 nm. Suitable for CW-power as well as pulse energy measurements. Optometer P-9710 with high dynamic range and precise pulse energy mode.
P-21 + ISD-30-SiIGA	Si + InGaAs 400 -1800 nm	300 mm Ø Integrating sphere	100 mm Ø	25nW @630nm 20nW @900nm 200nW @1300nm 280nW @1550nm	4W @630nm 5W @900nm 40W @1300nm 55W @1550nm	Power and radiation protection measurement of laser rangefinders. Integrating sphere detector with 300 mm barium sulfate sphere for laser power measurement from 400 nm - 1800 nm. Suitable for CW-power as well as pulse energy measurements. Optometer P-9710 with high dynamic range and precise pulse energy mode.
PLL-1701	Ext. InGaAs 400-1800 nm	Internal Integrating sphere	FC connector			lHigh-Speed optometer with FC-input and small internal integrating sphere. Implemented are a linear and logarithmic amplifier.
PLL-1701 + ISD-3P-IGA	InGaAs 800 -1800 nm	30 mm Ø Integrating sphere	5 mm Ø			High-Speed optometer with FC-input and small internal integrating sphere. Implemented are a linear and logarithmic amplifier. Larger integrating sphere detector (30 mm diameter, 800 nm - 1800 nm wavelength ranger) connected via BNC-connector.