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Laser Radiation Measurements

Gigahertz-Optik GmbH produces instruments for measuring optical radiation from the lasers and laser diodes that are widely used in measurement, analytical and telecommunication equipment as well as in sensor technologies. The product range includes instruments for measuring continuous, modulated and pulsed radiation.

Example laser radiation measurements from different application fields are presented on this page.

On this page application examples from different application areas of laser radiation measurement technology are presented.

+49 (8193) 93 700-0

Pulse Energy Measurement of Divergent Laser Beams/LiDAR

Laser diodes used in distance measuring devices have a diverging elliptical beam profile with typical peak powers of up to 100 W. They are operated in a short pulse width, low pulse frequency mode with low average power. 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. Therefore, pulse energy and pulse waveform must each be measured separately.

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. Additionally, the small area of the photodiode can only detect a portion of the entire laser beam profile. The photodiode and laser beam must be carefully aligned due to non-uniformity in the laser beam profile. This method is entirely suitable for the measurement of the relative pulse waveform, which is needed together with the pulse energy to calculate the peak power.


UV Laser Power Measurement in UV Laser Confocal Microscopes

UV laser scanning confocal microscopes provide sample illumination from a UV laser via a microscope objective which results in a highly convergent beam. Therefore, in order to measure the total radiated power in the beam a detector with a large acceptance angle is required.

The photodiodes routinely used for radiometric measurements have a two-dimensional sensor surface. At shallow angles a portion of the incident radiation is reflected from the surface thereby reducing the measured radiation power. This can result in a significant measurement error when measuring the highly convergent beam of a confocal microscope. By appropriately combining the photodiode with a compact integrating sphere this source of error can be minimized. This design of detector offers a large acceptance angle and can also withstand higher laser power levels. Due to the size and shape of an integrating sphere detector it must be possible to rotate the microscope’s sample table to enable positioning of the detector.

Example Configuration: Radiant Power and Energy Measurement of Laser Rangefinders

The measurement of laser power is not always possible with off-the-shelf instruments due to the design and specifications of the laser. For such cases, the ability to configure systems from modular components is a good approach.

In the following example, a laser power meter was required to measure the intensity of a combined laser rangefinder and laser pointer system. For the laser rangefinder the energy of single pulses and pulse sequences (at 1550nm) need to be measured and for the laser pointer the average power is specified (at 830nm). The maximum beam diameter is 45 mm. The system must be traceable to a National Metrology Institute in order to obtain the certificate of conformity for Class 1 according to EN 60825-1 classification.