Search

Optical frequency combs have become a very powerful tool in metrology and beyond thanks to their ability to link radio frequencies with optical frequencies via a process known as self-referencing. Typical self-referencing is accomplished in two steps: the generation of an octave-spanning supercontinuum spectrum and the frequency-doubling of one part of that spectrum. Traditionally, these two steps have been performed by two separate optical components. With the advent of photonic integrated circuits, the combination of these two steps has become possible in a single small and monolithic chip. One photonic integrated circuit platform very well suited for on-chip self-referencing is lithium niobate on insulator - a platform characterised by high second and third order nonlinearities. Here we show that combining a lithium niobate on insulator waveguide with a silicon photodiode results in a very compact and direct low-noise path towards self-referencing of mode-locked lasers. Using digital servo electronics the resulting frequency comb is fully stabilized. Its high degree of stability is verified with an independent out-of-loop measurement and is quantified to be 6.8 mHz. Furthermore, we show that the spectrum generated inside the lithium niobate waveguide remains stable over many hours.

In this work we describe the design, fabrication and testing of a mass-balanced planar x/y-scanner designed for parallel-probe storage applications (see Fig. 1a). We explore electrostatic actuation as an alternative to electromagnetic actuation. To increase the shock resistance, mass-balancing is used and the scanner is fabricated by deep reactive ion etching through a complete wafer. To move the scan table in both positive and negative x and y directions, four comb drives are used. The comb-drive fingers are tapered to increase the generated force without decreasing the minimum trench width.