Collimated diode laser module and pocket laser pointer both produce a spot of light. So why there are such huge difference in price?

The simple answer is: It all depends. There can be variability in any type of product. While the desired output of a laser pointer and collimated diode laser module is similar, the real numbers might be different due to:

• Laser pointers are mass produced so this helps reduce costs. They generally have less complex and less robust drive electronics since the power source is supposedly well defined - a set of batteries. There may be no corrective optics for the astigmatism and elliptical aberrations of the typical laser diode - at a distance, your spot isn't a nice round Gaussian profile. There is probably just a single cheap plastic lens glued in place.

• Diode laser modules are more of a specialty item used inside other equipment and for optics research and development or special design for customers' requirements. Production volumes are not as high. They usually (but not always) have high quality driver circuits designed to protect the sensitive laser diode from moderate abuse - noisy power, for example. Many have high quality optics including additional elements for correction of the laser diode aberrations.

In the end, it is probably the mass production that is the most significant factor in keeping costs down. There is also another difference between the two which relates to output power:

• For a laser pointer, the power rating - if it can be believed at all - is a maximum only with fresh batteries under the right conditions on a very good day, or possibly just the 5 mW maximum for Class IIIa (which is the most that is legal in the USA for a laser pointer). The actual power could be much less and may decrease rapidly as the batteries are drained.

• For a diode laser module (from a reputable manufacturer at least), the power rating is likely to either be what they actually measured for that sample or a guaranteed minimum value after warm up (power goes down with increasing laser diode temperature), or after some number of hours of operation. Thus, the actual output power could be much more under some set of conditions. The CDRH safety sticker will still list an upper bound but it will likely be much higher than the module's power rating.

PS

For more information of the laser, you can link to ”Sam's Laser FAQ” http://www.repairfaq.org/sam/lasersam.htm