Fig. 1 Layout of the fully integrated PIC. Redundant tunable laser sources are followed by semiconductor optical amplifier (SOA) pre-amplifiers. The signal passes through a 32 channel splitter and is then tuned in both phase and amplitude for each channel. The channels feed a surface grating array where the beam is emitted at an angle determined by wavelength in the θ axis and by relative phase in the ψ axis. A graded index lens images the remaining beam power into the far field and where it is measured by a photodiode array for on-chip feedback.

Fig. 2 Schematic of tunable Vernier ring laser with (a) two gain regions and (b) one gain region.

Fig. 3 (a) Calculated angular power distribution for 4, 5, and 6 μm spacing between emitters with an inset of the calculated side mode separation between main lobe peak and side lobe (measured where the side lobe intensity rises to −10 dB relative to main lobe peak which is where the useful field of view ends) vs. emitter pitch, (b) calculated far field beam full width half max (FWHM) vs. emitter pitch for 8, 16, and 32 channels, (c) calculated beam FWHM vs. side lobe separation based on varying emitter pitch, and (d) calculated number of resolvable spots (i.e. side lobe separation divided by beam width) vs. side lobe separation based on varying emitter pitch.

Fig. 4 Calculated far field for (a) uniform and (b) Gaussian emitter spacing using no relative phase or output power differences between channels. Calculated far field for (c) uniform array with linear relative phase shift and (d) Gaussian array with linear relative phase shift adjusted for irregular spacing to tune the main lobe to −10°. The Gaussian array performs better when considering the full signal, but (c)-(d) illustrate the larger tuning range of the uniform array within a field of view while maintaining greater than 10 dB side mode suppression.

Fig. 5 (a) A cross-section of the calculated refractive index profile for the GRIN lens. The cross section is taken at 250 μm into the lens. (b) Simulated intensity passing through the lens with zero phase shift between channels. The focal length is marked at 473 μm.

Fig. 6 Calculated lens output power for linear relative phase delays between adjacent channels in degrees.

Fig. 7 (a) Confocal microscope picture of the fully integrated beam-steering PIC. The chip size is y x z cm2. (b) Photos of the mounted and wire-bonded chip placed in a water-cooled copper block and (c) the PCB attached to the assembly.

Fig. 8 (a) Schematic of the test setup and (b)-(c) images of the test setup.

Fig. 9 SEMs of (a) laser and pre-amplifier gain elements, (b) InP tapers for adiabatic transitions between III/V gain and silicon waveguides with magnified images of the taper tip immediately following mesa etching, (c) completed laser and pre-amplifier, (d) ring mirror and (e) ring-to-bus coupler.

Fig. 10 (a) Measured peak wavelength vs. tuning power from one mirror, (b) measured optical spectra, and (c) measured output angle vs. predicted output angle (from wavelength measurement). A wavelength tuning efficiency of 0.28 nm/mW was achieved and the tuning efficiency of predicted and measured angle were 0.030 and 0.034 °/mW respectively. Since the laser was integrated on-chip it was unable to be measured individually so the full spectra SMSR is not available.

Fig. 11 (a) Transmission through a 2 mm Mach-Zehnder test structure showing a phase modulator dependency on power implying a thermo-optically dominated device on the integrated chip. Test run measurements of similar devices showing (b) 14 mA/π tuning efficiency with data and modeled fit and (c) a 3dB bandwidth greater than 50 MHz.

Fig. 12 (a) Responsivity and (b) quantum efficiency of the 470 μm long photodiodes at −5 V.

Fig. 13 SEMs of (a) input waveguides and the beginning of the GRIN lens, (b) a zoomed in SEM of insufficiently etched holes that led to lens distortion of the beam, and (c) a close-up image of the photonic crystal lens etched spots.

Fig. 14 SEM of output grating array, lens and photodiode array.

Fig. 15 Two-dimensional beam-steering plots spanning 23° in ψ and 3.6° in θ.