Integrated Photonic Polarization Synthesizer and Analyzer

Abstract

Polarization-resolved control and measurement of the optical field are essential for a wide range of photonic systems, including coherent communication, polarimetric sensing, and quantum information processing. We present a photonic integrated circuit that enables the generation and analysis of arbitrary polarization states. The device provides reconfigurable access to the full polarization degree of freedom of coherent light within a single integrated platform. We experimentally demonstrate arbitrary polarization state generation spanning the Poincare sphere, as well as Stokes vector measurement on chip. Unlike conventional Stokes measurements that rely on direct detection, polarization analysis utilizing this architecture is intrinsically non-destructive, preserving the optical signal for further optical domain processing. The devices are fabricated in a commercial foundry using CMOS-compatible processes, enabling scalable and reproducible integration. By combining polarization generation and analysis in a compact and stable photonic circuit, this work eliminates the need for external polarization optics and provides a foundation for robust, polarization-enabled photonic integrated systems.

Figures (6)

• Figure 1: (a) X-Z Cross section of the uniform PSGC with a 70 nm partial etch. Inset: Zoom in on a several local periods of the PSGC. (b) X-Z Cross section of the FDTD simulations of the device at 1.550 $\upmu$m with a simulated insertion loss of -2.9 dB. Roughly half of the light is lost toward the substrate as a result of the vertical symmetry of the grating layer. (c) X-Y Cross section of the uniform PSGC showing four-fold symmetry. (d) X-Y Cross section of the FDTD simulations displaying the emission profile of the grating when excited from the left and right ports with equal amplitude, in-phase modes. The emitted grating profile has a 86.4$\%$ mode overlap with a 10.4$\upmu$m MFD gaussian mode.
• Figure 2: Schematic diagram of the integrated photonic polarization synthesizer/analyzer. The architecture relies on a two-stage binary tree of Mach-Zehnder Interferometers interfaced with the four ports of a normal incidence polarization splitting grating coupler.
• Figure 3: Experimental setup for characterizing the PIC as an arbitrary polarization synthesizer. The fundamental quasi-TE mode of the PIC is excited via a fiber coupled external laser source. The phase shifter settings of the photonic mesh are managed via a National Instruments DAQ which allows for complete control of the complex amplitudes entering the four ports of the PSGC. The output of the PSGC is imaged onto a polarimeter which operated on the principles of the rotating quarter-wave plate method.
• Figure 4: Generated states as characterized by the rotating quarter-wave plate polarimeter. (a) Sets of basis pairs demonstrating horizontal and vertical linear polarization states, positive and negative $45^{\circ}$ linear polarization states, as well as right-hand circular and left-hand circular polarization state. (b) Intermediate linear polarization states between the horizontal, vertical, positive and negative $45^{\circ}$ linear poles. (c) Intermediate elliptical polarization states between the right-hand circular, left-hand circular, positive and negative $45^{\circ}$ linear poles. (d) Intermediate elliptical polarization states between the horizontal, vertical, right- and left-hand circular poles.
• Figure 5: Normalized Stokes parameters measured by operating the PIC as a polarization analyzer. The input polarization states are set to horizontal, vertical, positive and negative 45$^\circ$ linear by aligning the input fiber to test structures designed to accept linear polarization states.