Diffractive Optics - Gentec Electro Optics - #1

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92 Monitors Energy Detectors Power Detectors OEM Detectors Calorimeters Diffractive Optics Beam Diagnostics prese ntation diffractive optics For Online MonitoringHBSBeam PropagationDirection10°0th Order, P = 97.55 W1st Order (1%), P = 0.9755 WPower DetectorAverage Power Measurement2nd Order (<< 1%)*Beam Diagnostic ToolFor Beam Proling20°APPLICATIONUses the largest part of the beamEnergy DetectorPulsed Energy MeasurementPhoto DetectorPulse Shape, Pulse Width, Repetition Rate* Characterization of 2nd order ratio upon requestP = 100 W OVERVIEW What if you need to measure the performance of the beam in real-time while your application is online? You cannot insert or remove optical components or interrupt the beam either. How do you do that? One way is to divert a small fraction of the beam that is an exact replica of the main beam. Sampling is also a solution if the beam is too “hot” for your diagnostic instruments to handle. In either case, almost all of the main beam is available to do its job. One approach is to use something like a moveable mirror to sample in time. The beam is interrupted and diverted for small slices of time. A big disadvantage though is that the time sampler provides average values so it is not well suited for real-time operation, especially with pulsed lasers. The other way is to continuously divert a tiny fraction of the beam to another angle while the main beam passes through, along its original line. However it is done, the sample needs to be a low power replica of the main beam. The components or methods suitable for real-time beam sampling are summarized in Table 1. The particular requirements of an application will narrow down the list of acceptable methods. All of these methods provide a decent replica of the main beam in the sampled beam and all can withstand reasonably high power. If it is important that the polarization of the sample be the same as the beam, then the Mirror and the Frustrated Total Internal Reflection are not good choices due to mixing of the horizontal and vertical polarizations. Low sampling fraction is very good. This means that most of the beam passes on to the application with a tiny percentage being diverted. The Mirror and Hole Matrix remove much more energy from the beam than the other components which is a problem for many applications. Sampling Real-Time Beam Sampling Figure 1. Example HBS Application Pulsed ND:YAG, 1064 nm, 1J @ 100 Hz (100 W)