Laser Components has launched a range of anti-reflection (AR) coatings to help bring down the losses associated with back reflections within optical systems.
When light passes from one medium into another, back reflections occur, which equates to approximately four per cent loss for air to glass interfaces. Without AR coatings, considerable losses would result in optical systems in which light passes through a number of interfaces.
After passing through 10 interfaces, only 66 per cent of the original output power would reach the end of the system. Back reflections on lens surfaces not only reduce output power, but can also focus light down to small spots creating high power densities. For laser applications this can be damaging to other surfaces and boundaries such as lens doublets.
The Laser Components' range includes single layer AR, V-AR and U-AR, broadband AR, double AR and multiple AR coatings.
The single layer AR coating is the simplest coating, consisting of a single MgF2 layer of λ/2 thickness. Optimum performance is achieved when the refractive index of the coating is nC = √ nSubstrate. This coating is therefore mostly used on materials that have a high refractive index such as sapphire or soft flint glasses such as SF10.
V-AR and U-AR coatings consist of several layers. They are optimised for one wavelength or for a small range of wavelengths and have the best performance for BK7 and fused silica glasses. V-AR coatings achieve a residual reflection of < 0.2 per cent per surface at 1064nm and U-AR coatings achieve < 0.1 per cent at an even larger wavelength range. V-AR and U-AR coatings are available from 193nm to 3000nm.
Broadband anti-reflection (BBAR) coatings cover a wavelength range from 193nm to 1600nm. Standard ranges are supplied by Laser Components and custom BBAR coatings for other wavebands are offered.
Double AR and Multiple AR Coatings are designed for laser fundamental wavelengths and its harmonic, or doubled, wavelength. Examples include 1064nm + 532nm, and 800nm + 400nm. With these coatings residual reflections of <0.3 per cent at 1064nm and <0.4 per cent at 532nm can be achieved. Laser Components has a quadruple AR coating capability for all Nd:YAG wavelengths (1064nm, 532nm, 355nm, and 266nm).
Laser Components also offer custom AR coatings. These coatings are applied to, for example, exotic materials or prisms with incident angles varying from 0° to angles exceeding Brewster’s angle.