A substrate is the basic component of a laser optic. Plano substrates, curved substrates for mirrors, lenses for laser and sensor applications, and prisms are all available for delivery. A coating can be applied to all of these substrates.
Uncoated plano substrates with and without wedges.
Substrates with plane surfaces are used, for example, as bending mirrors, dichroic mirrors, or windows. The finest polished optics with a planarity of l/10 are normally used in laser applications.
The polish specification of substrates depends on the application. When used as mirrors, the glasses are finely polished on at least one side. When used in transmission, both sides of the substrate are polished to laser grade quality.
Just as coatings and substrates are both designed for specific applications, for optimal performance of a laser optic they should also be designed to correlate with each other. Most notably the optical characteristics, but also the mechanical characteristics of the substrate are to be considered.
Round Plane Substrates
LASER COMPONENTS offers different round plane substrates. Including:
Rectangular/Square Plane Substrates
There is also choice of the rectangular/square plane substrates:
If the laser beam has to be deflected by a very small angle in transmission, so-called wedge windows are used. Furthermore, they are used as mirrors or output couplers when back reflections occur that render the laser instable, even though an AR coating has been applied. In order to ensure the high quality of the components, only finely polished substrates with an extremely high surface figure are used.
Depending upon the application, wedge windows with an angle of 0.5° are often used to suppress a back reflection into the resonator. These features can be found in the PI series.
Wedge angles of 1°, 2°, and even 3° have proven themselves useful when used as windows for beam deflection. Wedge substrates with large angles can be found in the the PL series.