Agilent, HP, Hewlett-Packard, and Keysight are well-known manufacturers of lasers that provide high-quality optical solutions for various industries and applications. These lasers belong to the 5517 series which include models like 5517C, 5517B, and 5517D, among others. These lasers offer exceptional performance and precision, making them ideal for applications such as distance measuring interferometry, laser interferometry, and metrology. They are widely used in industries such as aerospace, defense, telecommunications, and manufacturing. One of the advantages of these lasers is their high stability and accuracy, ensuring reliable and precise measurements. They have low drift rates and excellent frequency stability, making them suitable for demanding applications that require accurate measurements over long periods. These lasers also feature advanced control and modulation capabilities, allowing users to customize and optimize their performance. They offer options for external modulation, frequency locking, and laser beam steering, providing versatility to meet specific application requirements. Examples of these lasers include the Agilent/HP/Keysight 5517C, which is commonly used in laser interferometry. It offers exceptional frequency stability, making it suitable for high-precision measurements. The 5517B is another popular model known for its low drift and excellent long-term stability. The 5517D is a newer model that combines the features of the previous models with enhanced performance and functionality. Overall, the lasers from Agilent, HP, Hewlett-Packard, and Keysight are highly regarded for their precision, stability, and versatility, making them a preferred choice for various optical applications.