Design and characterization of a laser diode pumped external cavity for particle measurement applications

Current particle measurement devices for use in applications such as clean-room air monitoring systems utilize a He-Ne laser as the pump source for an external resonant measurement cavity. Strides toward future development of particle measurement instrumentation aim to reduce cost and device size, thus making laser diodes a favorable choice. Laser diodes, however, exhibit several characteristic properties which must be addressed in order to achieve stable operation. We have devised and tested a simple cost efficient technique to ensure accurate particle measurement without the cost or bulk associated with laser stability instrumentation. We have investigated the power stability of a laser diode pumped external resonant cavity optical setup. We propose that the described system can be used for particle measurement applications by using the detected cavity output power as a trigger signal for a second detector, used to measure scattered light from particles pumped through the laser beam.