Determining Damage Thresholds for Laser Measurement with a Slit Based Profiler - Photon Inc - #1

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Technical Note Determining Damage Thresholds for Laser Measurement with a Slit Based Profiler Measuring lasers can be a daunting task, particularly as the power or energy levels get higher. Many applications require that precise information about laser beam sizes be known, but these lasers may be capable of damaging the profilers. The slit-based profiler, such as the Photon NanoScan is ideally suited for measuring these higher power lasers, because it can accept a relatively high powered beam directly, without attenuation. Nonetheless there are limits. Determining these limits can be complicated, especially if the laser is operated in the pulsed mode, since both power and energy can contribute to the damage threshold. Continuous wave lasers are measured in Power, or watts per cm2; pulsed lasers are measured in Energy, or Joules per cm2. The energy is a function of the average power and the pulse frequency and is inversely related to the frequency. The formula for this is simply: Therefore the higher the frequency, the lower the energy. Some lasers have adjustable frequency, and it is very important to remember that if the frequency is lowered the energy goes up; e.g., a perfectly safe level at 80 kHz may damage the scanhead at 60 kHz. Photon Inc. Tel: 408.226.1000 Fax: 408.226.1025 Email: beam@photon-in.com www.photon-inc.com Determining Damage Thresholds for Laser Measurements with a Slit Based Profiler B010908726