Magnesium fluorideformula

Magnesium fluorideionic or covalent

A pellicle is a very thin optical-grade nitrocellulose membrane (or film) stretched over an aluminum ring and bonded in place. In function, a pellicle beamsplitter serves the same purpose as a common plate beamsplitter. Upon close inspection, a plate (or "mirror-type") beamsplitter produces two reflected beams for a single input beam. One is a reflection off the first (or front) surface and the second is off the second (or back) surface. The result is what is called a "ghost image" or secondary reflection. In addition, plate beamsplitters slightly displace the transmitted beam laterally from the input beam due to the thickness of the glass substrate (1-3mm depending on size). For these reasons, plate beamsplitters minimize these effects and offer the best performance when the glass thickness is minimal, the coated surface is oriented toward the source, it is inserted in a collimated beam, and the back surface is AR (anti-reflection) coated. Pellicles on the other hand eliminate ghost images because of the thinness of the membrane (2 microns), since the first and second surface reflections are superimposed. In addition, absorption is imperceptible. Pellicles can be used uncoated as well as coated for several different reflection percentages. Also because of their lightweight, pellicles can be used when weight issues prevent the use of heavier plate or cube beamsplitters. However, since pellicles are extremely delicate, they have several drawbacks. The membrane can be easily broken (and cannot be repaired), thus they require caution in handling and mounting. Pellicles are also very sensitive to mounting stresses and atmospheric vibrations (including acoustic noise and compressed air), both can cause the film to warp or vibrate and therefore result in reflection and transmission distortions. Pellicles are highly desirable for interferometric applications since there are no ghost images, no change in the optical path length, and no chromatic aberrations with converging beams. However due to their cost and delicate nature, they are often not selected for the majority of applications requiring a beamsplitter.

Please select your shipping country to view the most accurate inventory information, and to determine the correct Edmund Optics sales office for your order.

Magnesium fluorideuses

MgF2 windows are well suited for deep-UV applications, even extending into the vacuum-UV region. They offer >50% transmission at 120 nm, making them suitable for use with excimer laser systems, as well as applications involving the Hydrogen Lyman-α line at 121 nm. Thorlabs' MgF2 windows are also usable in the UVA, UVB, visible and IR ranges, with approximately 94% transmission from 200 - 1000 nm, and approximately 95% transmission from 1 - 6 µm.

Thorlabs' Magnesium Fluoride windows are available in Ø1/2" and Ø1" sizes. They offer excellent transmission from deep in the ultraviolet region to the mid-infrared. MgF2 windows are extremely durable and introduce minimal aberrations. Thorlabs' MgF2 windows are cut with the optical axis parallel to the c-axis of the crystal to minimize birefringence.

Knowledge Center/ Technical Frequently Asked Questions/ Optics Frequently Asked Questions/ Beamsplitters/ What is a pellicle beamsplitter and when should I use it?