Lasers; and Parts and Accessories for Lasers-Namely, Laser Plasma Tubes, Laser Reflectors and Holders Therefor, Laser Power Supplies, Laser Power Monitors, Laser Power Meters and Attenuators Therefor, Laser Etalons and Assemblies Therefor, Laser Light Regulators, Laser Wave Length Selectors, Laser Polarization Rotation Apparatus, and Laser Stabilization Measuring Apparatus