High-resolution subsurface microscopy of CMOS integrated circuits using radially polarized light.

Under high numerical aperture (NA) conditions, a linearly polarized plane wave focuses to a spot that is extended along the E-field vector, but radially polarized light is predicted to form a circular spot whose diameter equals the narrower dimension obtained with linear polarization. This effect provides an opportunity for improved resolution in high-NA microscopy, and here we present a performance study of subsurface two-photon optical-beam-induced current solid-immersion-lens microscopy of a complementary metal-oxide semiconductor integrated circuit, showing a resolution improvement by using radially polarized illumination. By comparing images of the same structural features we show that radial polarization achieves a resolution of 126 nm, while linear polarization achieves resolutions of 122 and 165 nm, depending on the E-field orientation. These results are consistent with the theoretically expected behavior and are supported by high-resolution images which show superior feature definition using radial polarization.

Octave-spanning super-continuum from a silica photonic crystal fiber pumped by a 386 MHz Yb:fiber laser.

We report octave-spanning super-continuum generation in a silica photonic crystal fiber (PCF) pumped by a compact, efficient, mode-locked all-normal dispersion Yb:fiber laser. The laser achieved 45% optical-to-optical efficiency by using an optimized resonator design, producing chirped 750 fs pulses with a repetition rate of 386 MHz and an average power of 605 mW. The chirped pulses were compressed to 110 fs with a loss of only 4% by using multiple reflections on a pair of Gires-Tournois interferometer mirrors, yielding an average power of up to 580 mW. The corresponding peak power was 13.7 kW and produced a super-continuum spectrum spanning from 696-1392 nm.