Low-loss chip-scale programmable silicon photonic processor

Abstract

Chip-scale programmable optical signal processors are often used to flexibly manipulate the optical signals for satisfying the demands in various applications, such as lidar, radar, and artificial intelligence. Silicon photonics has unique advantages of ultra-high integration density as well as CMOS compatibility, and thus makes it possible to develop large-scale programmable optical signal processors. The challenge is the high silicon waveguides propagation losses and the high calibration complexity for all tuning elements due to the random phase errors. In this paper, we propose and demonstrate a programmable silicon photonic processor for the first time by introducing low-loss multimode photonic waveguide spirals and low-random-phase-error Mach-Zehnder switches. The present chip-scale programmable silicon photonic processor comprises a 1×4 variable power splitter based on cascaded Mach-Zehnder couplers (MZCs), four Ge/Si photodetectors, four channels of thermally-tunable optical delaylines. Each channel consists of a continuously-tuning phase shifter based on a waveguide spiral with a micro-heater and a digitally-tuning delayline realized with cascaded waveguide-spiral delaylines and MZSs for 5.68 ps time-delay step. Particularly, these waveguide spirals used here are designed to be as wide as 2 μm, enabling an ultralow propagation loss of 0.28 dB/cm. Meanwhile, these MZCs and MZ-Ss are designed with 2-μm-wide arm waveguides, and thus the random phase errors in the MZC/MZS arms are negligible, in which case the calibration for these MZSs/MZCs becomes easy and furthermore the power consumption for compensating the phase errors can be reduced greatly. Finally, this programmable silicon photonic processor is demonstrated successfully to verify a number of distinctively different functionalities, including tunable time-delay, microwave photonic beamforming, arbitrary optical signal filtering, and arbitrary waveform generation.

Self-Configuring GHz-Scale Multichannel Silicon Photonic Filter Using a Resonator-Assisted Discrete-Fourier-Transform Interferometer

“…More importantly, low-phase-error 2 × 2 thermo-optic MZIs with 2 μm-wide phase shifters (corresponding to heaters 1, 2, 12, 13) are introduced for tuning the coupling coefficients of the resonators and the amplitude of the delay lines. Such a design is beneficial for reducing the power consumption and calibration complexity because the random phase errors due to the fabrication imperfection is negligible, compared to conventional MZIs with singlemode phase shifters. , …”

“…In total, there are 16 heaters for the present N-WDM MOF configuration. In order to reduce the waveguide loss and the chip size, we use the design of a broadened Archimedean waveguide spiral with a tapered Euler-curve S-bend 36 for the delay lines as well as the resonators. The broadened silicon photonic waveguides are designed with a core width of w co = 2 μm to achieve an ultralow loss of 0.28 dB/cm even when using standard fabrication processes.…”

“…Such a design is beneficial for reducing the power consumption and calibration complexity because the random phase errors due to the fabrication imperfection is negligible, compared to conventional MZIs with singlemode phase shifters. 36,38 As a result, the fabricated chip in Figure 3b has a footprint of 2.14 mm 2 by using a silicon-on-insulator wafer with a 220 nmthick silicon core layer and a 2 μm thick buried oxide (BOX) layer. All the heaters are led to the bottom side of the chip for wire-bonding to a printed circuit board.…”

Freeform Metasurface-Assisted Waveguide Coupler for Guided Wave Polarization Manipulation and Spin–Orbit Angular Momentum Conversion

“…Integrated photonic devices, which can process massive amounts of information with high speed, low energy consumption, and functional versatility, have been explored for decades. − Such ultracompact on-chip platform has been widely used in various applications, including optical communication, biosensors, virtual reality, and integrated quantum optics. − To increase the channel number and thus the information capacity of photonic integrated circuits, different dimensions of light, such as frequency, spatial mode, and polarization of guided waves, could be efficiently utilized. − Particularly, waveguide couplers play a critical role in connecting free-space light and guided waves in diverse integrated photonic systems. Conventional grating couplers, prism couplers, or other sophisticated fibers and waveguides allied systems remain limited in functional flexibility. ,− Cascaded strategies consisting of grating couplers, mode converters, and polarization rotators are standard solutions to obtain desired modes despite their large footprints, low efficiencies, and high processing difficulties. − Developing a multifunction integrated free-space light coupler has attracted substantial attention in recent years, given the potential to significantly enhance the compactness of optical on-chip platforms. However, a multifunctional coupler is still challenging to implement using conventional design strategies (see the discussion in Supporting Information, Note S1). − …”

Decoupling and Parameter Extraction Methods for Conical Micro-Motion Object Based on FMCW Lidar

“…They also obtain structure and shape information about the detected object [ 20 ]. Compared to the pulse lidar, the advantage of the FMCW lidar in distance measurement is that the frequency modulation laser source can be integrated into a chip [ 21 ], and the received beat frequency represents the distance and Doppler information about the object. Useful information about the object can be detected and extracted in this beat frequency domain [ 22 ].…”