Hongliang Chen

Polarization management is a key technique in integrated photonic circuits. In this paper, a low loss and compact TE-pass polarizer based on lithium niobate on insulator (LNOI) platform is presented. By utilizing subwavelength grating (SWG) metamaterials and inverse design algorithm, the TE₀ mode propagates through the SWG region with minimal loss, while the TM₀ mode is efficiently coupled out and suppressed through shape-optimized algorithm, thereby achieving an expanded bandwidth of the polarization extinction ratio (PER). With a footprint of 66 μm, the polarizer exhibits low insertion loss (IL) < 0.174 dB and a PER > 10 dB over 176 nm (1465–1641 nm), reaching 33.2 dB at 1550 nm. Furthermore, the proposed polarizer demonstrates superior overall performance, along with promising potential for polarization management and mode conversion in high-performance LNOI-based integrated photonic systems.

We propose and experimentally demonstrate a high-performance polarization beam splitter (PBS) on silicon-on-insulator (SOI) platform. The PBS integrates a shape-optimized reflective polarizer based on anti-symmetric Bragg gratings with a mode demultiplexer realized through an inverse-designed adiabatic coupler. Experimental results reveal an optical bandwidth of 160 nm (1285–1360 nm and 1500–1585 nm) with extinction ratio ER > 20 dB, and a narrower bandwidth of 120 nm with ER > 30 dB. The device also features low insertion loss (IL) with ${\rm IL}_{\rm TE}$ < 1 dB for TE polarization and ${\rm IL}_{\rm TM}$ < 0.3 dB for TM polarization across the entire operational wavelength range. This PBS stands out as one of the few devices capable of covering the crucial optical bands for fiber-to-the-home (FTTH) networks (1.31, 1.49, and 1.55 μm) while achieving both low IL and high ER. This development marks a significant step forward in polarization diversity for photonic integrated circuits (PIC), supporting next-generation communication systems.

In this study, we designed and experimentally demonstrated a compact polarization-insensitive 2 × 2 3 dB quasi-adiabatic coupler based on B-spline curves and shape optimization. By using the supermode to enable the segmented shape optimization of the coupler, we significantly reduced the computational cost of the optimization process. The numerical simulation results exhibited a power imbalance below ±0.46 dB and an insert loss (IL) of less than 0.09 dB over a broad bandwidth of 140 nm, ranging from 1490 nm to 1630 nm for both the TE and TM polarizations, with a compact coupling length of 12 µm. The experimental results showed a power splitting ratio within 3 ± 0.46 dB over the range of 1525 nm–1600 nm for the TM mode and 1576 nm–1610 nm for the TE mode. This broadband and low-loss 3 dB coupler is suitable for microwave photonic (MPW) applications, enabling efficient polarization-independent signal processing in integrated photonic systems.

We demonstrate a low phase error waveguide bend designed through the use of adjoint shape optimization. This bend features low loss and crosstalk, and its 1.8 μm width and 4 μm radius reduce phase error caused by width deviations to about one-sixth of that in conventional arc bend. Utilizing this bend, we developed a cascaded MZI-based coarse wavelength division multiplexing (CWDM) filter with high tolerance to random fabrication variation of waveguide width. The spectral shift of the filter is about five times smaller than that of conventional filter under both global and local width deviations. Additionally, due to the small bend radius, we achieved a compact total device footprint of 0.01 ${\bf mm^{2}}$ . The filter was then fabricated using a 193-nm dry lithography process. Experimental results show that the filter exhibits a loss of 2.34dB and crosstalk of $\mathbf{-}$ 25.85dB. Measured spectra from different die across the wafer are highly consistent, with spectral shifts of only 3.67nm due to deviations in waveguide thickness. Our design strategy offers a solution for the application of phase-sensitive devices.

The 2 × 2 3-dB couplers are one of the most widely used and important components in silicon photonics. Here, we propose an ultra-broadband and compact 2 × 2 3-dB adiabatic coupler defined by b-splines and optimized with an efficient supermode-injected adjoint shape optimization. By employing mode adiabatic evolution and mode coupling at two different wavelength ranges, respectively, we achieve an ultra-broad bandwidth of 530 nm from 1150 nm to1680 nm with a power imbalance below ±0.76 dB in a compact coupling length of 30 µm according to our simulation results. The supermode-injected adjoint shape optimization can also be applied to the design of other photonic devices based on supermode manipulation.

In this paper, we design and experimentally demonstrate an eight-channel cascaded Mach–Zehnder interferometer (MZI) based Local Area Network (LAN) Wavelength Division Multiplexing (WDM) (de)multiplexerwith channel spacing of 800 GHz on a silicon-on-insulator. By cascading a three-stage MZI, eight target wavelengths are (de)multiplexed. The length difference of the third-stage MZI delay arms is adjusted so that the output channels skip the guard band. In order to keep the central wavelength of each channel from shifting, we utilize a wide waveguide for the phase delay arm in MZI to achieve large fabrication tolerance, and the multi-mode interference (MMI) couplers as power splitters with weak dispersions. The measurement results of the fabricated device show the precise wavelength alignment over the whole working wavelength range.

Spatially-variant morphological operators are studied extensively in the literature for image processing. In this paper, first, we model a reasonable spatially-variant morphological regularization method based on nonlocal amoeba kernel for general inverse problems in imaging (e.g., denoising, deblurring and super resolution). The novel regularization term which provides spatially adaptive prior information, resulting in a powerful overall setting for blurred image with seriously noises. And second, the inverse problems in imaging are formulated as to minimize the TV cost function which consists of data-fidelity term and proposed morphological regularization term. For optimization problem, Bregman iteration algorithm and operator splitting technique are effectively used in this stage in order to minimize the TV functional. Finally, numerical results on inverse problems show that the proposed method gives better performance than state-of-the-art algorithms in terms of both PSNR and visual perception, which demonstrates the efficiency of our proposed algorithm.