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Molded Plastic Aspheres
Click to Enlarge | Raw Data
The shaded region represents the recommended wavelength range for the uncoated acrylic. This data was measured using a 2 mm thick sample.
Aspheric lens are designed to eliminate spherical aberration, which allows for the spot size and collimation of a monochromatic beam of light to be diffraction limited. The Molded Plastic Aspheric Lenses offered here are available uncoated or with an antireflection coating deposited on both sides for either the 400 - 700 nm or 650 - 1050 nm range. In addition, these aspheres are fabricated from acrylic, which is half as dense as N-BK7, making them ideal for weight-sensitive applications.
In laser diode systems, difficulties with aberration correction are compounded by the beam's high divergence angle. Since individual spherical lenses can refract light at only small angles before spherical aberration is introduced, three or four elements are often required to collimate laser diode light. In contrast, a single aspheric lens collimates without introducing spherical aberration. When used to collimate light, the lens should be oriented so that the side with a larger radius of curvature (i.e., the flatter surface) faces the point source.
Conversely, when coupling into fiber, it is often necessary to focus the laser light to a diffraction-limited spot. Single spherical elements are typically not capable of achieving such a small spot size because spherical aberration is the limiting factor. Since the aspheric lenses are corrected to eliminate the spherical aberration, only diffraction limits the size of the focal spot. For focusing applications, the lens should be oriented so that the side with a smaller radius of curvature (i.e., the more curved surface) faces the source.
To mount the Ø3 mm or Ø6 mm aspheres sold on this page, we recommend the LMR05 fixed lens mount along with either the LMRA3 mounting adapter for Ø3 mm optics, or the LMRA6 mounting adapter for Ø6 mm optics.
Please see the Graphs Tab for AR Coating Details
These high-performance multilayer AR coatings have an average reflectance of less than 0.5% (per surface) across the specified wavelength ranges and provide good performance for angles of incidence (AOI) between 0° and 30° (0.5 NA). For optics intended to be used at large incident angles, consider using a custom coating optimized at a 45° angle of incidence; this custom coating is effective from 25° to 52°. The plot shown below indicates the performance of the standard coatings in this family as a function of wavelength. Broadband coatings have a typical absorption of 0.25%, which is not shown in the reflectivity plots.