1 × 12 Unequally spaced waveguide array for actively tuned optical phased array on a silicon nanomembrane

Abstract

We present an experimental demonstration of an optical phased array implementation on silicon nanomembrane. The integrated on-chip array configuration is non-uniform and avoids grating lobes inside the field of view during beam steering while allowing the waveguide separation to be large enough to prevent optical coupling. A 1 × 12 multimode interference beam splitter uniformly excites the arrayed waveguides. Individually controllable micro-heaters modulate the optical phase in the arrayed waveguides. A beam steering angle of 10.2° in a silicon planar guide equivalent to an effective steering angle of 31.9° in air is demonstrated at 1.55 μm.

High-density waveguide superlattices with low crosstalk

“…Halfwavelength pitches are routinely used in microwave-phased arrays, but have been a challenge for optical-phased arrays (OPAs) 20,40,41 . The current waveguide superlattice can be used in certain silicon-based OPA configurations 18,19 to deliver phasemodulated signals to an array of output waveguide-facets (or waveguide-gratings) radiating signals at l/2 pitches, which results in l/2-pitch optical-phased arrays. Note that the width difference has no significant impact on the OPA performance and the associated phase-shift difference can be readily compensated (see detailed discussion in Supplementary Note 4).…”

“…The superlattice lengths in this work are sufficient for some applications such as wavelength (de)multiplexers 25 , spectrometers and optical-phased arrays 18,19 , where only a short segment of high-density waveguide array is needed at the input/output to achieve high wavelength resolution or maximal beam steering range and then the dense waveguides can be spread out through waveguide bends to connect/couple to other part of the devices/systems. In longer superlattices, our simulations show that the mean crosstalk does not change significantly and the standard deviation of crosstalk tends to increase very slowly with L (see Supplementary Fig.…”

“…Waveguide arrays are among the cornerstones of such systems. For example, waveguide arrays are widely used in emerging applications such as optical-phased arrays [18][19][20][21] , space-division multiplexing 22 and chip-scale optical interconnects 23,24 , and conventional applications such as wavelength-division multiplexers 25,26 . On the other hand, a waveguide array or a waveguide lattice can also be viewed 27 as fully analogous to a periodic chain of atoms, which lends itself to a broad spectrum of fascinating scientific possibilities ranging from Anderson localization of light 28,29 to parity-time symmetric effects 30 .…”

“…On the other hand, a waveguide array or a waveguide lattice can also be viewed 27 as fully analogous to a periodic chain of atoms, which lends itself to a broad spectrum of fascinating scientific possibilities ranging from Anderson localization of light 28,29 to parity-time symmetric effects 30 . Thus far, in most studies, the pitch associated with such relatively simple waveguide arrays/lattices has been typically large, ranging from a few micrometres to tens of micrometres (or a multiple of wavelengths) 18,19,21,31,32 . As such, the inter-coupling between waveguides can be generally weak, which helps to reduce crosstalk.…”

Highly integrated optical phased arrays: photonic integrated circuits for optical beam shaping and beam steering

“…Following from the design criteria, as discussed above, such arrays should be as large as possible, with the emitters closely spaced. Initial work in this field first focused on one-dimensional (1D) arrays fabricated in indium phosphide [13] and silicon photonic technology [14]. For example, this latter realization used a 12-channel edge emitting array, tunable over 32°.…”