Enhanced Reflectivity: One end of the ruby rod is partially silvered to enhance the reflectivity of the laser light. This silvered surface acts as a mirror, reflecting the laser light back into the ruby rod, allowing it to undergo multiple passes through the gain medium. This multiple pass amplification significantly increases the laser's output power and efficiency.
Output Coupling: The other end of the ruby rod is partially silvered to achieve optimal output coupling. A partially silvered surface allows a controlled amount of laser light to be transmitted through it while reflecting the rest back into the rod. This fine balance between reflection and transmission ensures that the laser operates within its desired output power range.
Control of Laser Modes: Partial silvering also helps in controlling the laser's spatial modes. It allows the selection of specific laser modes by controlling the amount of reflected and transmitted light within the resonant cavity. This enables the laser to operate in a single longitudinal mode or a desired transverse mode, depending on the requirements of the application.
Prevention of Unwanted Reflections: The silvered ends of the ruby rod prevent unwanted reflections from the edges of the rod. Any uncontrolled reflections can lead to unwanted losses and distortions in the laser output. Partial silvering helps to minimize these effects, ensuring a clean and stable laser beam.
Heat Dissipation: Silver has a high thermal conductivity, which helps in dissipating heat generated within the ruby rod during laser operation. This efficient heat dissipation prevents thermal damage to the ruby and maintains a stable laser output.
Overall, the partial silvering of the ruby rod ends in a ruby laser serves multiple functions, including enhancing reflectivity, achieving optimal output coupling, controlling laser modes, preventing unwanted reflections, and facilitating heat dissipation. These factors contribute to the efficient operation and performance of the ruby laser.