3D-printed optical probes for wafer-level testing of photonic integrated circuits.

Wafer-level probing of photonic integrated circuits is key to reliable process control and efficient performance assessment in advanced production workflows. In recent years, optical probing of surface-coupled devices such as vertical-cavity lasers, top-illuminated photodiodes, or silicon photonic circuits with surface-emitting grating couplers has seen great progress. In contrast to that, wafer-level probing of edge-emitting devices with hard-to-access vertical facets at the sidewalls of deep-etched dicing trenches still represents a major challenge.

Ultra-short pulsed off-axis digital holography for imaging dynamic targets in highly scattering conditions.

A single-shot digital holography system using an ultra-short pulsed laser is demonstrated to be very effective in suppressing the multiple-scattering noise associated with imaging dynamic targets in highly scattering environments, such as biological tissues and fuel injection systems. A planar off-axis reference wave configuration is used to generate a fixed carrier spatial frequency in the recorded holograms in order to separate coherent signal from incoherent noise in Fourier transformed holograms. The single-shot imaging system does not require averaging between multiple shots and can capture images of transient phenomena, such as the formation of diesel fuel injection sprays, and can overcome the problem of mechanical vibrations for recording holograms in industrial and laboratory environments.

Design of diamond-turned holograms incorporating properties of the fabrication process.

Recently, the fabrication of computer-generated holograms by diamond face turning with a nanometer-stroke fast tool servo (nFTS) has been demonstrated. Existing methods for the design of diamond-turned holograms account for their spiral-shaped surface topology and the fact that only the phase of a wave field can be modulated. Here we present an algorithm enabling the additional consideration of two important fabrication-related properties: the shape of the diamond tool used and the limited control frequency of the nFTS.

Holographic projection based on diamond-turned diffractive optical elements.

We introduce an approach to generate holographic data for diffractive optical elements fabricated by means of a diamond-turning process. The aim is to project a predefined intensity distribution in the far-field domain of the corresponding diffractive surface. The method takes into consideration typical constraints that result from the fabrication process, such as the spiral path of the turning tool and the fact that only the phase distribution of the incident light can be manipulated.