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Reconfigurable optical directed logic circuits (RODLC) aim to perform arbitrary logic operations using the optical switch network, in which the electrical signals regarded as the logic operands are applied to the optical switch to control the propagation of light over time, and the logic operation results are obtained at the output ports of the optical switch network in the form of light. In this paper, a novel RODLC is proposed and experimentally demonstrated by utilizing an optical switch array with the prosperous optical mode division multiplexing (MDM) technology to perform arbitrary logic functions. As a proof of concept, a RODLC with two optical mode (de)multiplexers and twelve thermo-optic microring resonators on a silicon-on-insulator substrate is fabricated based on standard microfabrication technology. To demonstrate its reconfigurability to perform arbitrary logic functions, eight logic operations: NOT, AND, NAND, OR, NOR, XOR, XNOR, as well as one combination operation of four-operand, with the operation speed of 10 Kbps are successfully implemented as examples. The demonstrated RODLC characterized with reconfigurability, scalability, and ability for large-scale integration, will contribute to the flourishing development of optical computing and information processing in large-scale optical hybrid integrated circuits.

Lithium niobate on insulator (LNOI) has been demonstrated as a promising platform for photonic integrated circuits (PICs), thanks to its excellent properties such as strong electro‐optic effect, low material loss, and wide transparency window. Herein, a monolithic PIC for high‐speed data communication application on a lithium‐niobate‐etchless platform with silicon nitride (Si3N4) as a loading material is proposed and demonstrated. The fabricated PIC consists of four racetrack resonator modulators and a pair of four‐channel mode (de)multiplexers, which shows high data modulation rate of 70 Gbps for single channel and the total data throughput reaches up to 280 Gbps. To the best of knowledge, this is the first demonstration of PIC consisting of high‐speed electro‐optical modulators and (de)multiplexers with such high data capacity on Si3N4‐LNOI hybrid platform, which opens up new avenues for achieving large‐scale monolithic integration on LNOI platform in future.

Dielectrically loaded thin-film lithium niobate (LiNbO3) on insulator (LNOI) platforms have enabled a range of photonic integrated circuit components, such as high-speed optical modulators, switches, and nonlinear devices, while avoiding the direct etching of the LiNbO3 thin film. Silicon nitride (Si3N4) is one of the most attractive dielectric loading materials as it has a similar refractive index and transparency window to LiNbO3 and can be deposited and patterned by mature fabrication processes. The patterning of Si3N4 opens the opportunity to fabricate grating couplers in the same fabrication step, providing efficient optical interfaces for wafer-scale testing. In this paper, we investigate and demonstrate single-step etched grating couplers on a Si3N4-LNOI (X-cut) platform. The grating couplers (straight and curved) are designed and fabricated for TE-polarized modes along the Y and Z crystallographic directions, considering the LiNbO3 crystal’s birefringence. The experimentally demonstrated coupling losses are as low as 4.02 and 4.24 dB along the crystallographic Y and Z directions, respectively. The corresponding peak wavelengths are 1609 and 1615 nm, respectively. The measured 3-dB bandwidths are wider than 70 nm for both crystallographic directions. We also numerically investigated the influence of fabrication variations and the fiber angle on the transmission. To the best of our knowledge, this work is the first demonstration of grating couplers with different light propagation directions on the Si3N4 loaded LNOI platform.

We propose a novel approach to demonstrate an add-drop filter based on microfiber knot resonator (MFKR). The two coupled regions and four ports (including input port, through port, drop port, and add port) of this device are formed using the same one microfiber. By reconnecting the ends of the through and add ports with other two microfibers, this structure could serve as an add-drop filter, which is a key building block in the fields of optical networks and optical information processing system. The MFKR-based add-drop filter with the quality factor (Q-factor) of 21 000 and a diameter of 740 μm is demonstrated successfully. The intrinsic loss and extinction ratio are about -2 and 18.5 dB for the drop port, and -4.6 and 10.7 dB for the through port, respectively. The fabrication process also shows the feasibility and simplicity of this device.

Abstract We experimentally demonstrate a reconfigurable electro-optic directed logic circuit which can perform any combinatorial logic operation using cascaded carrier-injection micro-ring resonators (MRRs), and the logic circuit is fabricated on the silicon-on-insulator (SOI) substrate with the standard commercial Complementary Metal-Oxide-Semiconductor (CMOS) fabrication process. PIN diodes embedded around MRRs are employed to achieve the carrier injection modulation. The operands are represented by electrical signals, which are applied to the corresponding MRRs to control their switching states. The operation result is directed to the output port in the form of light. For proof of principle, several logic operations of three-operand with the operation speed of 100 Mbps are demonstrated successfully.

We propose and demonstrate a directed optical logic circuit that can perform the XOR and XNOR logic operations consisting of two cascaded microring resonators, i.e., an upper waveguide and an under waveguide. No waveguide crossings exist in the circuit, which is very useful to improve the signal quality and reduce the insertion loss of the device. As proof of principle, XOR and XNOR logic operations with the speed of 10 kb/s are successfully demonstrated. In addition, numerical simulation results indicate that the length difference between the upper waveguide and the under waveguide can change the output spectrum characteristics of the device, which acts like a Mach-Zehnder interferometer (MZI).

In this paper, we propose a reconfigurable electro-optic logic circuit, which can perform any combinatorial logic operations using a microring resonator (MRR)-based optical switching array. The operands are represented by electrical signals, which are applied to the corresponding MRRs to control their switching status. The operation results are directed to the output port in the form of light. For proof of concept, the circuit consisting of four thermooptic MRR-based optical switches is fabricated on the silicon-on-insulator (SOI) substrate using the commercial complementary metal-oxide-semiconductor (CMOS) fabrication process. Finally, several logic operations of four operands with the operation speed of 10 kb/s are demonstrated successfully.

We propose a novel approach to demonstrate an add-drop filter based on microfiber knot resonator (MFKR). The two coupled regions and four ports (including input port, through port, drop port and add port) of this device are formed using the same one microfiber. By reconnecting the ends of the through and add ports with other two microfibers, this structure could serve as an add-drop filter, which is a key building block in the fields of optical networks and optical information processing system. The MFKR-based add-drop filter with the quality factor (Q-factor) of 21 000 and a diameter of 740 μm is demonstrated successfully. The intrinsic loss and extinction ratio are about -2 and 18.5 dB for the drop port and -4.6 and 10.7 dB for the through port, respectively. The fabrication process also shows the feasibility and simplicity of this device. [ABSTRACT FROM AUTHOR]

We simulate and experimentally observe a tunable Fano resonance in a mutual coupling microring resonator (MRR) system which is comprised of two cascaded micro-ring resonators. The scattering matrix model is employed to analyze the modulating characterization of the Fano resonance by changing the effective refractive index of MRRs, and the simulation results indicate that the Fano resonance is the sharpest when two MRRs' resonances are coincident. The Fano resonance device is fabricated on a silicon-on-insulator substrate using the standard complementary metal-oxide-semiconductor (CMOS) fabrication process. The experimental results show that the spectrum of the Fano resonance can be periodically tuned and flipped by applying forward-bias voltages to integrated micro-heaters above the MRRs. The proposed device has unique merits such as compact size, simple structure, CMOS compatible fabrication process, and large-scale integration, which is a promising candidate for high-sensitivity biochemical sensing and low power optical switching/modulating in future. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate a mode-splitting device using a microring resonator (MRR) with a feedback coupled waveguide (FCW). For the proposed device, a pair of counter-propagating coupled modes exist in the MRR owing to the FCW, which is different from traditional ways of introducing roughness or center defects. We obtain the splitting of the transmission spectrum with a splitting wavelength of 0.37 nm and a notch depth of 21.87 dB. Moreover, the temporal coupled-mode theory is adopted to fit the experimental results and analyze the dependence of the transmission spectrum on the coupling coefficient κ. The experimental results are in good agreement with the simulations. [ABSTRACT FROM AUTHOR]

In this paper, we propose an optical mode switch based on two cascaded multimode interference (MMI) couplers. After a fundamental mode divided into two equal-power fundamental modes in the first MMI coupler, the thermo-optic effect is employed to modulate the phase of the two fundamental modes before directed to the next MMI for the purpose of mode switching. By adjusting the electric signals applied to the modulation arms, the proposed device can implement mode switching in three states: (a) one first-order and two fundamental modes simultaneously output, (b) one first-order mode output, and (c) two fundamental modes output. As a result, the simulated excess losses are −0.29 dB, −0.10 dB, and −0.63 dB, respectively. [ABSTRACT FROM AUTHOR]