The type of lasers commonly used in laser interferometers for metrology applications are _____.

Explanation:

Gas lasers:

• Gas lasers are the most commonly used type of lasers in laser interferometers for metrology applications. The reason for their widespread use lies in their stability, coherence, and ability to produce high-quality beams. Here are some detailed points explaining why gas lasers are preferred:

1. High Stability: Gas lasers, such as the Helium-Neon (He-Ne) laser, are known for their high frequency and amplitude stability. This is crucial in metrology applications where precise and accurate measurements are required. The stability ensures that the laser's output remains consistent over time, reducing the chances of measurement errors.

2. Long Coherence Length: Coherence length is a measure of how monochromatic (single-wavelength) the laser light is. Gas lasers typically have a long coherence length, which is essential for interferometry. A longer coherence length means that the laser light can maintain its phase relationship over longer distances, which is necessary for producing clear and accurate interference patterns in interferometry.

3. High Beam Quality: Gas lasers produce high-quality beams with low divergence and minimal beam distortion. This high beam quality ensures that the laser light can be precisely directed and focused, which is important for accurate interferometric measurements.

4. Narrow Linewidth: Gas lasers have a very narrow linewidth, meaning they emit light at a very precise wavelength. This narrow linewidth is important for high-resolution measurements in metrology, as it reduces the uncertainty in the measurement of distances.

5. Reliability and Longevity: Gas lasers are known for their reliability and long operational life. This makes them suitable for continuous and long-term use in metrology applications, where consistent performance over time is essential.