طلب مساعدة في اجهزة قياس طاقة الليزر Nd:YAG

Laser Power / Energy Measurement Today
By Dr. Ephraim Greenfield
Ophir Optronics

The laser industry is advancing steadily with new wavelengths, higher powers and energies, and new applications all the time. As the power, energy and variety of new lasers advances, so measurement of these lasers has to advance.
The basic technology of laser power/energy measurement has not changed in the last 10 years. There are still three basic ways to measure laser power and energy
a. The first type of laser measurement device is the thermopile detector that measures the amount of heat flowing through the detector by its heating effect on an array of thermocouples
Thermopile laser measurement is almost wavelength independent, durable and reliable. It is therefore the mainstay of laser power/energy measurement. It cannot, however, measure repetitive pulses or very low powers and energies

b. The second type of measurement device is the photodiode detector that converts light impinging on a photodiode into a current.
These photodiode detectors are based on a semiconductor P-N junction. When photons of light with energy greater than the characteristic band gap energy of the photodiode hit the detector, they create an electron hole pair that is collected in the associated circuit.
Photodiode detectors are very sensitive, have a wide dynamic range and are very linear at low powers. However, they are very wavelength dependent as shown in the graph, necessitating calibration over a complete range of wavelengths. They also saturate at low powers, becoming nonlinear. Therefore this type of power meter is mainly for low powers. With no additional filters, they are linear up to a few mW and with filters they can measure as much as 3 Watts.
c. The third type of detector is the pyroelectric detector consisting of a crystal that polarizes when heated.
Pyroelectric detectors are particularly useful for repetitive pulses and can measure up to thousands of pulses per second. They are also quite sensitive. They are not particularly durable, however, so for higher energies and powers, an attenuator/diffuser is placed in front of the sensor crystal to lower the energy on the pyroelectric crystal