Our lab uses a home-built high NA lens based on a design by Curtis Volin from GTRI. Our original lens was performing poorly; it collected lots of light, but did not focus it terribly tightly. So, using the freeware raytracer Beam4 we have tweaked another one of Volin’s designs and built a new lens:
This design uses four Thorlabs stock lenses and achieves a numerical aperture of roughly 0.42. With the rebuilt lens we’re now collecting approximately 15% more light and focusing it into a spot about half as large. Still not diffraction limited, but progress!
