Reflection/transmission confocal microscopy characterization of single-crystal diamond microlens arrays

Using the method of photoresist reflow and inductively coupled plasma dry etching, we have fabricated microlens arrays in type-IIa natural single-crystal diamond, with diameters down to 10 µm. The surface profile of the microlenses was characterized by atomic force microscopy and was found to match well with a spherical shape, with a surface roughness of better than 1.2 nm. To characterize the optical properties of these diamond microlens arrays, a laser scanning reflection/transmission confocal microscopy technique has been developed. This technique enabled the surface profile of the microlenses to be measured simultaneously with optical parameters including focal length and spot size, opening up an application area for confocal microscopy.