A laser pen, often referred to as a laser pointer, is a handheld device that emits a focused beam of light through a process called stimulated emission. Typically, this device is used to highlight or point out specific locations, objects, or details during presentations, educational lectures, or even astronomical observations. Laser pens come in various colors, with red, green, and blue being the most common. Among them, green laser pens are usually more visible due to the human eye's higher sensitivity to green light.

The basic design of a laser pen includes a laser diode, a power supply (often batteries), and a lens or optics to focus the light into a narrow, directed beam. While their compact size makes them very convenient for personal or professional use, their power and safety classification are critical aspects. Laser pens are typically classified by their power output — Class 1 and Class 2 lasers are generally safe for brief use, while Class 3 or above require more caution due to potential eye injury risks.

In education and corporate presentations, laser pens are widely used to guide attention to specific information on a whiteboard, projector screen, or digital display. This helps improve communication efficiency and audience engagement. In astronomy, powerful green laser pens are used to point out stars or constellations in the night sky. These beams can stretch for miles, making them highly visible even under dark skies, thus helping instructors or tour guides give accurate demonstrations.

In construction and alignment work, certain laser pens are integrated with measurement tools to aid in leveling, surveying, or distance calculations. These high-precision devices help engineers and technicians ensure exact alignments in architectural or industrial tasks. Similarly, in the medical field, laser pens can serve as tools for minor therapeutic applications such as acupuncture or pain relief, using low-level laser therapy (LLLT). However, these are specialized medical-grade devices and not the standard commercial laser pens.

Laser pens are also popular among pet owners, especially for cats. The light beam gives the animal a target to chase, providing both exercise and entertainment. However, care should be taken to never shine the beam directly into the pet’s eyes, as even low-powered lasers can cause retinal damage over time.

Despite their usefulness, laser pens can be misused. For example, pointing them at aircraft is illegal in many countries due to the risk of distracting or temporarily blinding pilots. Similarly, pointing them at people’s eyes can cause serious harm, including permanent vision damage.

To use a laser pen safely, always follow the manufacturer's guidelines and local regulations. Avoid pointing the laser at reflective surfaces, moving vehicles, or people. Store the pen safely out of reach of children, and use protective eyewear if working with higher-class lasers.

In summary, a laser pen is a compact and versatile tool with applications ranging from professional presentations and astronomy to construction and healthcare. While they offer convenience and precision, responsible usage is essential to ensure safety and compliance.