Features

• Preconfigured for Our Ø9 mm Mounted Aspheric Lens Housings
• Fits Other Housings Using Various Adapters (Refer to the Accessories Tab)

Fiber Couplers

Thorlabs offers two kinds of fiber couplers: those that couple free-space laser beams into fiber optic cables (KT110), and those that couple the output from a laser diode into a fiber optic cable (KT112). The single mode and multimode fiber couplers have high-precision differential adjusters, which provide submicron translation.

Recommended coupling optics for our KT110 and KT112 cables include those from our C230TM and C220TME series of aspheric lenses.

Principles of Spatial Filters

The input Gaussian beam has a spatially varying "noise" intensity. When a beam is focused by an aspheric lens, the input beam is transformed into a central Gaussian
spot (on the optical axis) with side fringes that represent the unwanted noise. The radial position of the side fringes is proportional to the spatial frequency of the noise.
By centering a pinhole on the central Gaussian spot, the clean portion of the beam can pass while the noise fringes are blocked.

The diffraction-limited spot size at the 99% contour is given by D = λƒ/r where λ is the wavelength, ƒ is the focal length, and r is the input beam (1/e²) radius. A pinhole that is approximately 30% larger is chosen to allow the focused Gaussian spot to pass through the pinhole while blocking the noise fringes that are shifted off axis.