Red Laser Module - Class II

Overview

A LASER is a type of light source that is capable of emitting extremely coherent and collimated light. There are a variety of types of LASERs, each type with its own method of creating this coherent and collimated light. The type of LASERs used in our kits is called a diode LASER.

Figure 1: A K-Optics LASER in its housing, mounted on a tilt mount.

Tutorial

LASERs are extremely useful optical elements, the variety of areas in which they find use is staggering whether it be in academia or industry. In our kits the LASER serves mainly as a source of coherent light. Isolation of coherent light from incoherent light is a messy process which often requires darkness. Worse yet, acquiring coherent light from a general incoherent source is sure to reduce the intensity of the light at the other end of the experiment. Thus, a LASER is a perfect source for our experiments.

Mounting Options

To reduce the chances of LASER light pointing towards undesirable directions the housing is designed to block outgoing LASER light as long as the LASER is not assembled onto its tilt mount.

Animation

Figure 2: The LASER housing opens to allow light through only when the LASER is assembled to the mount.

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Certifications:

Red LASER Module: CLASS 2: VLM-635-60 - Specification Page: Download

Theoretical Background

Coherence is not a quality attributable to any light source, it is a strong condition on light, especially that of a polychromatic nature. Coherence quantifies the ability of light to interfere with itself, it defines how well each photon of light in a wave-packet is synchronized with its neighbors. This synchronization is manifest in every different property that can be attributed to light, including wavelength, polarization, and phase. It is these properties that allow LASER light to exhibit interference patterns.

Figure 2: An interference pattern between two coherent LASER beams. — Figure 3: An interference pattern between two coherent LASER beams.

As light sources, LASERs are far from trivial. The means by which they generate light is inherently quantum mechanical. When an atom is excited, it may emit its excess energy as a photon in appropriate quanta, which are atom-dependent, in order to arrive at its ground state. The photon can be emitted by two mechanisms: the first is called spontaneous emission and, as its name suggests, an atom spontaneously emits a random photon. The second mechanism is one where an existing photon outside of the atom forces it to emit another identical photon – i.e., stimulated emission. In a LASER the main mechanism is the latter, although many times the former acts as a seed. This stimulated emission ensures that each photon is emitted with exactly the same properties as the one which caused its emission, and thus coherence is guaranteed.

Coherence is not an absolute qualification. When considering coherence, we generally speak of coherence time or coherence length, both of which characterize the dependence of coherence on the difference in time and distance travelled by two waves, respectively.

Figure 3: Coherent vs. incoherent waves — Figure 4: Coherent vs. incoherent waves

The means of producing stimulated emission are varied, but a diode LASER relies on the incoming stream of current to excite electrons, which then undergo stimulated emission to produce coherent photons.

Safety Guidlines

When working with a Class II LASER (such as this), it is crucial to prioritize safety to prevent any potential risks to eyes and skin. These LASERs emit visible light at low power levels, which may not cause immediate harm but still pose a risk if proper precautions are not taken. Avoid directing the LASER beam towards reflective surfaces that could scatter the light, as well eyes and skin of humans or animals. Remember that even though Class 2 LASERs are considered relatively safe, responsible handling and adherence to safety guidelines are paramount to prevent any accidents or injuries.