Lasers classes

The light source for excitation of Nd YAG lasers may be a pulsed flashlamp for pulsed operation, a continuous-arc lamp for continuous operation, or a semiconductor laser diode, for either pulsed or continuous operation. The use of semiconductor laser diodes as the pump source for sohd-state lasers became common in the early 1990s. A variety of commercial diode-pumped lasers are available. One possible configuration is shown in Figure 8. The output of the diode is adjusted by composition and temperature to be near 810 nm, ie, near the peak of the neodymium absorption. The diode lasers are themselves relatively efficient and the output is absorbed better by the Nd YAG than the light from flashlamps or arc lamps. Thus diode-pumped sohd-state lasers have much higher efficiency than conventionally pumped devices. Correspondingly, there is less heat to remove. Thus diode-pumped sohd-state lasers represent a laser class that is much more compact and efficient than eadier devices. 

Another common laser class is that of gas lasers, which includes helium neon (HeNe) lasers, carbon dioxide (CO2) lasers, nitrogen lasers, and so on. The helium neon laser, widely used until the advent of the diode laser, was one of the first types developed and commercialized. As described above, it is a discharge-pumped gas laser, which generally produces an output measuring a few mW in power. 

Nomenclature Wavelength Nominal Ocular Hazard Distance / Nominal Ocular Hazard Distance with optics Optical Density / Optical Density with optics Laser Class... 

Figure 12.1 An optical tweezers-transducer. Based around an inverted miaoscope, all the major components are highlighted. The optical path of the ND-YAG (1064) trapping laser (class 3B) are enclosed for safety reasons. The Zeiss Axiovert and other components are mounted on a vibration isolation air table. Further details are given in the schematic shown in Figure 11.2 and in the text...

Accessible emission limit— The maximum accessible emission level permitted within a particular laser class. 

Over the past few years a better understanding of lasers has resulted in an evolution of classification systems for lasers. Before 2002 the older system of classification used Roman numerals with the most hazardous class being Class IV (see Special Topic 7.3.3.1 Old Laser Classification). As experience with lasers grew, the classification system was updated to include new defining specifications. Beginning in 2002 a newly revised classification system was phased in and was fully implemented in 2007. It is based on International Electrotechnical Commission (lEC) Standard 60825-1/ANSI Z136.1—2007 that separates lasers into four classes. Class 1 is the least hazardous, Class 4 is the most hazardous, and there are new subclasses." The classification of lasers is dependent on the dose of radiation that can be received from a laser. A brief description of these laser classes is presented in Table 7.3.3.2. 

Eye damage is most likely from beam exposure to laser class... 

The classification of lasers is dependent on the dose of radiation that can be received from a laser. A brief description of these laser classes is presented in Table 7.3.3.2. 

Finally, laser package marking which have a Class 4 carbon dioxide laser [Class 1 with the equipment enclosure in place and the door(s) closed] are used to physically mark the exterior of plastic and ceramic packages. Fumes can be created during the marking and create residues on the equipment surfaces and fume extraction filters. Plastic epoxy packages contain antimony trioxide as a fire retardant (typically 1-5%), and ceramic packages may contain beryllium. 

Some He-Ne lasers (Class 3b) used for alignment purposes... 

Except for certain R D uses, these lasers are typically embedded in the equipment and have interlocked cabinets that enclose the beam path and the point where the beam contacts the target. This makes the lasers Class 1 during normal operations, but they are considered Class 3b or 4 lasers when the safety interlocks are defeated. The most common operation where it is necessary to remove the beam enclosures and defeat the interlocks is during alignment of the laser beam. 

Table 5. Key Laser Safety Controls by Laser Class (Summarized from Ref. 21)...

The following is a summary for the laser classes following the ANSI guidelines used in the United States ... 

List and describe the ANSI-defined laser classes. 

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