To address the fundamental limitations of conventional InP/In0.53Ga0.47As P-I-N photodetectors, including their narrow spectral response range, low responsivity, and lack of intrinsic polarization sensitivity, this study demonstrates a Si-based vertical PdSe2/InGaAs/InP P-I-N heterojunction photodetector. This structure utilizes the inherent short-wave infrared absorption capability of InGaAs, the broadband absorption of PdSe2, and the inherent in-plane optical anisotropy of PdSe2, the device achieves record responsivities of 2.59 A/W at 1310 nm (3-fold to 5-fold beyond theoretical limits), 0.628 A/W (1550 nm), 8.99 mA/W (1850 nm), and 2.67 mA/W (2200 nm), extending detection beyond the cutoff wavelength of InGaAs. Exceptional polarization sensitivity yields polarization extinction ratios of 85.5 (1310 nm), 408.6 (1550 nm, 10-fold higher than state-of-the-art), 106.2 (1850 nm), and 55.5 (2200 nm). This synergy of anisotropy, junction carrier separation, and P-I-N architecture enables on-chip polarization-sensitive IR systems without external optics.

Abstract This paper proposes a dual-core hollow-core anti-resonant fiber polarization beam splitter (DHC-ARF PBS) that incorporates an incomplete circular cladding tube to enhance the design degrees of freedom of the device. The structure consists of four incomplete circular outer cladding tubes distributed at certain angles, two pairs of complete circular inner cladding tubes located in the vertical and horizontal directions respectively, and eight circular nested tubes are incorporated within them. The fiber forms two cores, A and B, with the gap between one pair of cladding tubes located horizontally serves as a coupling channel for regular power transfer between the dual cores. The influence of the structural parameters on the performance of the splitter was analyzed using the finite element method (FEM), and a parameter optimization design was carried out. Simulation results indicate that at a device length of 2.97 cm, covering the wavelength range from 1.48 μm to 1.6 μm with a polarization extinction ratio (PER) as low as −20 dB, demonstrating excellent beam-splitting capability. Furthermore, the higher-order mode extinction ratio (HOMER) exceeds 100 over a broad wavelength range from 1.32 to 1.71 μm, reaching a notably high value of 552.26 at 1.55 μm, which confirms outstanding single-mode performance. The fundamental mode transmission loss is less than 1.82 dB/m. The PBS has significant potential application value in optical communications and all-fiber systems.

The 2 μm wavelength band communication technology, with its prominent spectral resource advantages, has emerged as a key technological direction to break through the capacity bottleneck of conventional optical communication systems. As a crucial component of optical communication systems, high-performance optical modulators directly determine critical system parameters, including transmission rates, energy efficiency ratios, and integration levels. However, current high-speed modulators operating at the 2 μm wavelength still fail to match the performance of their well-established counterparts at 1.55 μm, posing a fundamental limitation to the practical viability of this emerging spectral window. Here, we designed high-performance modulators at the 2 μm band, based on a graphene-on-silicon slot waveguide. An electro-absorption optical modulator was designed with a voltage-length product of 0.113 V·cm, a low insertion loss of 1.9 dB, a high extinction ratio of 50.7 dB, a 3-dB modulation bandwidth of ∼520 GHz, and an energy consumption of 177.38 fJ/bit. Additionally, we proposed a refractive index modulator based on the platform, theoretically demonstrating four-amplitude shift keying modulation and quaternary phase shift keying modulation by using microring resonators. The study is expected to offer a low insertion loss and highly integrated modulator, advancing the development of 2 μm waveband communications.

For Pockels cells required by high-energy lasers, the current mainstream design adopts a square aperture. Pockels cells assembled with slab-shaped electro-optic crystals are a more suitable choice for Nd:YAG Innoslab hybrid cavities that directly output large single-pulse energies or for ring-cavity regenerative amplifiers with large cavity-mode size. This study constructs a Pockels cell using a single large slab-shaped BBO crystal, focusing on enhancing electric field uniformity within the crystal and reducing assembly stress, thereby achieving consistent optical field modulation across the entire aperture. The experiment first tested the extinction ratio, conoscopic interference pattern, and extracavity modulation characteristics of the electro-optic switch. The developed Pockels cell was then applied to a continuously pumped and pulsed-pumped Nd:YAG hybrid cavity laser. During continuous pumping, we attained an output power of 37.54 W, a repetition rate of 2 kHz, and a pulse width of 6.5 ns. During the pulsed pump, we also obtained an output energy of 21.3 mJ with a repetition rate of 100 Hz and a pulse width of 7.77 ns. Both of these results exhibited near-diffraction-limited beam output. Given the performance verification of the proposed packaging in our work, we expect this high-performance Pockels cell to provide support for the advancement of integrated optical laser systems and high-resolution metrology.

All-optical logic has the potential to overcome the operation speed barrier that has persisted in electronic circuits for two decades. However, the development of scalable architectures has been prevented so far by the lack of materials with sufficiently strong nonlinear interactions needed to realize compact and efficient ultrafast all-optical switches with optical gain. Microcavities with embedded organic material in the strong light-matter interaction regime have recently enabled all-optical transistors operating at room temperature with picosecond switching times. However, the vertical cavity geometry, which is predominantly used in polaritonics, is not suitable for complex circuits with on-chip coupled transistors. Here, by leveraging state-of-the-art silicon photonics technology, we have achieved exciton-polariton condensation at ambient conditions in fully integrated high-index contrast sub-wavelength grating microcavities filled with a π-conjugated polymer as optically active material. We demonstrate ultrafast all-optical transistor action by coupling two resonators and utilizing seeded polariton condensation. With a device area as small as 2 × 2 µm2, we realize picosecond switching and amplification up to 60x, with extinction ratio up to 8:1. This compact ultrafast transistor device with in-plane integration is a key component for a scalable platform for all-optical logic circuits that could operate two orders of magnitude faster than electronic counterparts.

Polarization-sensitive measurements provide rich information about material properties and enable a wide range of applications. Accurate calibration of polarimetry and ellipsometry systems is especially important in broadband spectral imaging instruments, where the performance of polarizers varies with frequency and manufacturing tolerances can introduce systematic errors. Terahertz time-domain polarimetry (THz-TDP) offers amplitude and phase information across a broad spectral range that encompasses many low-energy resonances of chemicals, yet THz polarimetry remains less developed than its infrared and optical counterparts. In this work, we present a generalized in situ calibration technique for THz-TDP imaging systems that uses a rotating polarizer placed over a reference mirror. The method accounts for the leaky, frequency-dependent response of the wire-grid polarizer and simultaneously extracts the polarizer response and system calibration parameters from the same measurement. We implement the approach on a handheld polarimetric THz scanner and demonstrate that including a leaky polarizer model yields more consistent and accurate calibration parameters across spectrum and the field of view, as compared to a simple model of an ideal polarizer. The method is validated using two wire-grid polarizers with different extinction ratios, illustrating that an accurate in situ calibration can be achieved even when the polarizer response is imperfect and unknown a priori.

Optical phase modulators are critical components in integrated photonics, but conventional designs suffer from a trade-off between modulation efficiency and optical loss. Two-dimensional materials like graphene offer strong electro-optic effects, yet their high optical absorption at telecom wavelengths leads to significant insertion losses. Although monolayer transition metal dichalcogenides (TMDs) provide exceptional telecom-band transparency for low-loss electro-refractive response, their practical implementation in phase modulators requires top electrodes to enable vertical electric field tuning, which typically introduces parasitic absorption. Here, we address this challenge by developing hybrid tungsten oxyselenide/graphene (TOS/Gr) electrodes that minimize optical loss while enabling efficient phase modulation in TMD-based devices. The UV-ozone-converted TOS (from WSe2) acts as a heavy p-type dopant for graphene, making the graphene transparent in the NIR region while enhancing its conductivity. Our complete device integrates a hybrid TOS/graphene transparent electrode with a hexagonal boron nitride dielectric spacer and monolayer WS2 electro-optic material on a SiN microring platform. This achieves a high modulation efficiency of 0.202 V·cm while maintaining an exceptionally low extinction ratio change of just 0.08 dB, demonstrating superior performance compared to modulators employing conventional electrodes. Our breakthrough in near-lossless phase modulation opens new possibilities for energy-efficient optical communications, photonic computing, and fault-tolerant quantum networks.

High-performance mid-infrared (MIR) linear polarizers are essential for advanced applications in polarimetric detection, thermal imaging and environmental monitoring. However, conventional implementations face a persistent challenge in simultaneously achieving high transverse magnetic (TM) wave transmission and extinction ratio (ER) while maintaining fabrication simplicity. Here, we present a 350 nm-pitch bilayer polarizer utilizing hydrogen-silsesquioxane (HSQ) gratings with collimated aluminum metallization. By leveraging HSQ's dual functionality as both the dielectric grating and electron-beam resist, our design enables a streamlined fabrication process: direct-write lithography followed by collimated thermal evaporation-eliminating the need for pattern transfer, a key limitation in conventional fabrication that degrades performance. A tailored spacer thickness can maximize TM transmission in the broadband MIR region by satisfying Fabry-Pérot resonance. Experimental results confirm the outstanding performance, including a 94% average transmission and a 30 dB extinction ratio across a 3-5 μm spectral range. The developed approach offers a promising strategy for MIR polarizers, successfully reconciling the traditionally competing demands of optical performance and easy fabrication.

Improvement of mode extinction ratio using a novel mode interference demultiplexing scheme

We report the conception and experimental demonstration of a tunable polarization splitter-rotator (PSR) integrated into a thin-film lithium niobate (TFLN) photonic platform based on a 45° PSR. The device operates over the C-band and leverages the thermo-optical tunability of TFLN to achieve precise and stable manipulation of the polarization in a millimeter scale footprint. The PSR exhibits a polarization extinction ratio of 23.3 dB on average near 1550 nm, enabling separation of both polarization channels. This performance highlights the potential of TFLN for dual-polarization applications in optical communications, sensing, and beyond.

Thin-film lithium niobate (TFLN) electro-optic modulators (EOMs) offer distinct advantages, including high speed, broad bandwidth, and low power consumption. However, their large size hinders the density of integration, which trades off with the half-wave voltage. Photonic crystal (PC) structures can effectively reduce the device footprint via the slow-light effect; however, they experience significant losses due to fabrication defects and sharp corners. Here, we theoretically demonstrate an ultracompact Mach–Zehnder interferometer (MZI) EOM based on a TFLN valley photonic crystal (VPC) structure. The design can achieve a high forward transmittance (>0.8) due to defect-immune unidirectional propagation in the VPC, enabled by the unique spin-valley locking effect. The EOM, with a small footprint of 21 μm × 17 μm, achieves an extinction ratio of 16.13 dB and a modulation depth of 80%. The design can be experimentally fabricated using current nanofabrication techniques, making it suitable for broad applications in optical communications.

ABSTRACT Atomic magnetometers (AMs) are among the most sensitive magnetic field sensors, with uses in magnetic anomaly detection, geosciences, and fundamental physics research. Despite notable progress, developing highly integrated, miniaturized components with high resolution, sensitivity, and efficiency for chip‐scale AMs remains a significant challenge. Here, we present a novel integrated polarization detection scheme based on a bifocal liquid‐crystal polarization metalens (LCPM) for chip‐scale AMs. By leveraging geometric phase and holographic synthesis principles, the LCPM efficiently separates and focuses left‐ and right‐handed circularly polarized light at the rubidium D1 transition wavelength (795 nm), achieving a high focusing efficiency of up to 80% and extinction ratios of 104 and 134 for the two channels. We demonstrate a prototype AM operating in the spin‐exchange relaxation‐free regime, achieving a high magnetic‐field sensitivity of 17 fT/Hz 1/2 and a dynamic range of ±4.8 nT. The proposed LCPM‐based scheme reduces the optical‐path volume by 94% compared to traditional polarization detection systems. Importantly, our method is compatible with large‐scale, cost‐effective production through established liquid‐crystal manufacturing lines, paving the way for high‐throughput fabrication of chip‐scale AMs. This innovation enables compact, affordable polarization detection with enhanced sensitivity of atomic sensors, opening new opportunities for high‐resolution biomagnetic imaging and quantum precision measurements.

Cavity-enhanced four-wave mixing lays the foundation for a variety of nonlinear applications such as wavelength conversion, parametric oscillation, Kerr frequency comb generation, etc. While the dramatic enhancement in nonlinear conversion efficiency is commonly attributed to the resonance quality factor, the influence of the resonance extinction ratio has often been overlooked. In this work, we uncover the pivotal role of the extinction ratio in FWM processes through integrated innovations in ring-bus coupler design. Pulley couplers are engineered to selectively excite TE and TM modes within microresonators, enabling precise control over polarization-dependent resonance excitation. We demonstrate that the extinction ratio of the cavity resonance directly dictates FWM efficiency. By optimizing the coupling conditions to achieve high extinction ratios (6.6 dB), we realize an 11.95 dB enhancement in FWM efficiency compared to low-extinction-ratio cavities (3.3 dB), in excellent agreement with theoretical predictions. These findings highlight the importance of designing microring resonators at critical coupling conditions to maximize nonlinear conversion efficiency. To the best of our knowledge, this is the first systematic investigation of FWM conversion efficiency using pulley couplers in the gallium phosphide-on-insulator (GaP-OI) platform. In addition, thermal bistability measurements quantify the material absorption-induced propagation loss, clarifying the dominant loss origin. The results presented here provide valuable insights into the development of highly efficient integrated Kerr nonlinear photonic devices, with significant implications for integrated quantum sources and other nonlinear photonic applications.

Dual-mode 1060 nm VCSELs based on oxide-confined elliptical apertures are presented here, showing an orthogonal polarization suppression ratio (OPSR) of 11.3 dB and a high 3 dB bandwidth of 33.6 GHz. 100 Gbps (PRBS15) PAM-4 signal transmission with a transmitter and dispersion eye closure quaternary (TDECQ) of only 0.98 dB and an energy to data radio (EDR) as low as 99.6 fJ/bit is reported. At the 106 Gbps IEEE standard, the TDECQ is 2.35 dB with an EDR of 125.15 fJ/bit. For 67 Gbps NRZ, the signal-to-noise ratio (SNR) is still 6.22, the extinction ratio (ER) is 4.75 dB, and the EDR is 198 fJ/bit. These VCSELs are highly promising for large bit rates, and more energy-efficient optical interconnects.

Plasmonic Y-waveguide full adder using power combiner/divider: high extinction ratio and terabit-scale bit rates in 20 μm footprint

We report a fiber-based source of femtosecond radiation that is spectrally tunable in the short-wavelength infrared region, delivering average powers at the multi-watt level. The system utilizes self-soliton frequency shifting in a hydrogen-filled hollow-core fiber, producing pulse trains at 1.1 MHz with integrated relative intensity noise below 0.3% and a polarization extinction ratio of 30 dB. This source constitutes an efficient and valid fiber-based alternative to optical parametric amplifiers for a variety of applications, including THz generation, multiphoton imaging, and high-harmonic generation.

ABSTRACT All‐dielectric metasurfaces supporting bound states in the continuum (BICs) provide promising avenues for achieving high‐Q resonances and multifunctional photonic devices. Here, we design a Si‐based metasurface composed of two tilted nanobars on a SiO 2 substrate. Full‐wave simulations reveal two quasi‐BICs (QBICs) and a Fano resonance, and these resonances are further validated by theoretical fitting using the Fano–Anderson model. The resonance mechanisms are elucidated through electromagnetic field distributions and Mie theory. By tuning structural and excitation parameters, high‐Q resonances (Q> 10 3 ) are achieved, and both the Q factor and resonant frequency exhibit strong robustness. Exploiting these properties, the metasurface provides six‐channel optical On–Off modulation with a maximum modulation depth (MD) of ∼100%, a minimum insertion loss (IL) of 0.016 dB, and an extinction ratio (ER) of 46.24 dB. Three‐channel refractive index sensing is also achieved, providing an absolute sensitivity of 326.63 nm/RIU, a relative sensitivity of 22.34/RIU, and a maximum figure of merit (FOM) of 2.1 × 10⁵. This work provides a practical approach to realize multi‐channel On–Off modulation and sensing in all‐dielectric metasurfaces, offering a valuable reference for the research of future multifunctional photonic devices.

The performance of the germanium D-shaped photonic crystal fiber modulator based on GST phase-change material is numerically studied using full vectorial finite element method. The performance of the optical modulator is investigated in the mid-infrared wavelength region of 2.3 to 3.5 µm. The proposed optical modulator includes 20 air holes. The suggested optical modulator consists of germanium as a background material with a GST film placed on a CaF 2 spacer to enable modulation. By electrically altering the GST phase from an amorphous phase to a crystalline phase, the transverse electric mode is significantly weakened due to strong coupling with the surface plasmon polariton mode formed on the GST layer’s surface, thereby generating the modulated signal. We compute the effective refractive index, confinement loss for both core modes, and extinction ratio for different geometric sizes. The present results show that the proposed optical modulator has a high extinction ratio of 310 dB for a device length of 3.2 mm.

HighlightsNew hybrid lithography enables efficient dual-periodic microstructure patterning.Double-layer grating shows a stable extinction ratio despite duty cycle changes.Sub-micron alignment is achieved using custom optics and alignment observation tools.Index-matching liquid improves pattern uniformity by reducing surface mismatches.

We demonstrate the effects of fiber birefringence on soliton trapping in two highly birefringent photonic crystal fibers. Linearly polarized ultrashort pulses are injected into the fiber in an anomalous dispersion regime, resulting in the generation of a soliton and a trapped pulse amplified through orthogonal Raman gain. The two orthogonally polarized pulse components are located at group-velocity matched wavelengths. Higher fiber birefringence leads to a larger polarization extinction ratio and greater spectral separation of pulse components. For a certain range of the input field polarization azimuth angles, the pulse components walk off in a more birefringent fiber, which prevents the formation of a single pulse. The experimental results are supported by numerical simulations.