Safety Shutters VS Dump Shutters

When used with laser beams, two types of shutters are applicable. The first type is a safety shutter. The U.S. Laser safety shutters are designed to be used inside of a laser resonator cavity (intracavity). When the shutter is in the deactivated state, the shutter flag closes blocking the beam path and all laser action ceases. The shutter flag is positioned normal to the beam path, and only momentarily sees laser radiation as it crosses the beam, and thus does not have to dissipate the power of the full laser beam. These shutters are primarily designed as a fast acting method to turn the laser beam on and off, and thus may be used with various types of safety interlock systems to prevent unwanted access.

The second type of shutter is called a dump shutter, and is designed to be used outside of the laser resonator cavity (extracavity). These shutters are normally used as process shutters, and merely gate the beam on and off without interrupting laser action itself. When the shutter is in the closed position the beam is deflected by the shutter flag and is redirected to an absorber. With these shutters, the shutter flag is used as a beam deflector, and is designed to reflect the laser beam at 90^o to the incident beam angle. On lower powered units, the flag is polished and plated, and acts as a reflector. On higher powered units the flag contains a dielectrically coated mirror. When using the beam dump shutter, the full power of the laser beam is redirected, and requires some mechanism to absorb and dissipate the beam power. To accomplish this, a beam dump absorber is normally used. The beam dump is designed to fully absorb the beam power and turn it into heat. The heat is then either dissipated by air in low powered units or water cooling in higher power units. Another method of dissipating the beam power is to direct the beam onto a surface absorbing power detector, which allows monitoring the beam power when the beam is deflected.

Both shutter types are driven by a DC rotary solenoid. The solenoid mechanisms have return springs such that if the solenoid fails electrically, the shutter flag will return to the closed (safe) position. Additional safety verification can be provide by optional shutter position switches. Normal activation time for the above shutters is less than 100 milliseconds. Special high speed shutters are available that open and close in less than 40 milliseconds.

During the shutter selection process, several important factors should be considered. First the user should decide whether the shutter will be used intracavity or extracavity. If the shutter is to be used intracavity the U.S Laser 1030 series of shutters is appropriate. These shutters accept beam diameters up to 15 mm, and normally are supplied on a carriage mount compatible with USL optical rail. If used on a system other than a USL system, the shutter is available less the carriage mount for direct mounting.

If an extracavity shutter is required, the selection process requires more information. Laser specific information such as beam diameter, wavelength, power or energy level, and pulse duration (if pulsed) is required to determine the appropriate deflecting mirror. The 1031 series of extracavity beam deflection shutter will accept beams up to 19 mm diameter, and power levels up to 2 KW. Once the deflection shutter is selected, a compatible beam dump absorber will be required. The 1039 series of beam dump absorbers are directly compatible with the 1031 beam dump shutters, and will effectively absorb and dissipate up to 2 KW depending on the model selected. All beam dump absorbers used at power levels over 10 watts will require water cooling.

Custom high speed and high power shutters are also available.

 See also: Product Catalog - Shutters