laser pointers selection guide    laser pointers selection guide

Image credit: Laserglow Technologies | Made in China

 

Laser pointers (sometimes known as laser pens) are compact, handheld laser devices. They are typically used to highlight an object or point of interest by illuminating it with a bright spot of colored light.

 

Laser Pointer Basics

As shown in the Lasers Selection Guide, all lasers consist of three components: an energy source (also known as a pump), a laser (or gain) medium, and an optical resonator; these components are shown in the image below. Essentially, the pump provides energy which is amplified by the gain medium. This energy is converted into light and is reflected through the optical resonator which then emits the final output beam.

 

laser pointers selection guide

Image credit: Enlighten Your Mind

 

 

While early laser pointers were pumped by helium-neon (HeNe) gas, nearly all modern laser pointers use electrically-powered laser diodes as their energy source. The image below shows a deconstructed laser pointer and identifies its main components. In the image, the 1064 nm laser diode — which is controlled by a separate circuit and current from a battery pack — represents the pump, the KTP/YAG crystal represents the pointer's gain medium, and the focusing barrel is the optical resonator.

 

laser pointers selection guide

Image credit: Karlsruher Institut für Technologie

 

Laser pointers are used in a variety of industrial, commercial, and consumer applications, including:

 

  • As pointing devices for educational and business presentations
  • For industrial distance measurement and leveling
  • Special effects in laser shows
  • As a beacon in emergency situations
  • Laser gunsights

 

Specifications

 

Wavelength and Color

The color of a laser pointer's dot or beam corresponds directly to the wavelength it emits. While all lasers are capable of emitting visible as well as ultraviolet and infrared light, laser pointers are typically confined to the visible spectrum due to the inherent need for a viewer to see its output.

 

Laser pointer colors often have a profound impact on the simplicity or complexity of the device. For example, a red laser pointer may consist of only a 671 nm laser diode, batteries to power the diode, and a simple lens to collimate the output beam. (Note that this is possible because the laser diode's output falls within the red spectrum.) Conversely, because laser diodes which output light in the green spectrum are not commonly available, green laser pointers must include more components. As seen below, a green laser pointer begins with an infrared 808 nm laser diode, which pumps energy through a yttrium aluminum garnet (YAG) crystal to further increase the beam's wavelength to 1064 nm. The energy then passes through a second crystal designed to double the radiation's frequency, therefore halving the beam's wavelength to 532 nm (which will produce a green output beam). Only after these changes in wavelength and frequency can a beam finally be emitted. This process is often replicated to produce blue and violet output beams.

 

The image below compares the physical structure of a red and a green laser pointer; note the increased complexity of the green device as noted above. The DPSS (double-pumped solid state) module shown within the green pointer is where frequency doubling takes place.

 

laser pointers selection guide

Image credit: Drexel University

 

Laser pointer colors, as well as their specifications and attributes, are listed below.

 

Beam color

Wavelengths (in nm)

Typical power

Notes

Red

622-780

 

Often consist of a single laser diode.

Yellow

577-597

Low (< 10 mW)

Largely unsuitable for pointers due to need for active cooling; often pulsed.

Green

492-577

 

Appears brightest; complicated device due to need for frequency-doubling to obtain color.

Blue

455-492

Often high (> 1 W)

Often uses frequency doubling; becoming more common and feasible.

Violet

390-455

Higher (up to 120 mW)

Often causes fluorescence; may appear blue due to proximity to ultraviolet range.

 

 

Output Power

A laser's output power refers to the strength of its beam and is measured in watts (W) or milliwatts (mW). Specifying a laser pointer's output power not only determines its relative brightness but also determines its safety class as discussed below.

 

Safety

As high power laser pointers have become widespread and freely available to consumers, manufacturers and industry groups have correspondingly increased awareness of the dangers of such devices. While most early laser pointers intended for use in classrooms were limited to 5 mW of power or less, inexpensive high power devices — emitting as much as 1000 mW of power — are now easily obtainable. Even a split-second exposure to a 200 mW laser emitting 100 yards away can cause permanent eye damage.

 

laser pointers selection guide

A typical laser warning sign, including specs and class.

Image credit: Keller Studio

 

To address the concerns above, the Center for Devices and Radiological Health (CDRH) — a division of the US Food and Drug Administration (FDA) — maintains a laser safety classification scheme based on six product classes. Internationally, lasers are specified by different classes described in the IEC 60825 standard. The table below describes both US domestic and international classes for laser safety.

 

laser pointers selection guide

Laser safety classes. Image credit: Erchonia

 

 

References

 

Laser Pointer Safety

 

Sam's Laser FAQ - Brightness Ratings and Laser Pointer Visibility


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