Search

In this letter, we experimentally demonstrate the first slow-light Mach-Zehnder modulator (MZM) on a hybrid ithin-film Lithium Niobate platform. The Bragg grating waveguides are served as phase shifters, which enhance the modulation efficiency with the slow-light effect. Compared with large-signal modulation efficiency ( $\text{V}_\pi \cdot \text {L} =0.67\,\,\text{V}\cdot $ cm) and an ultra-compact footprint (0.3 mm $\times1.2$ mm). Data transmission up to 60 Gbps and an on-chip insertion loss of 1.9 dB are also achieved. This modulator provides a potential solution for high-intensity integration, low-power transmission, and optical biosensing.

In this paper, we present a novel transmission line architecture in thin-film lithium niobate (TFLN) platforms to improve the velocity match between the microwave and the optical wave. Compared to conventional coplanar waveguide (CPW), the microwave index ($n_m$) of the proposed slotted electrodes can be optimized from 2.1 to 3 while maintaining the high modulation efficiency and 50-$\Omega$ impedance match. Equivalent-circuit model analysis and finite-element simulation are performed. The simulated half-wave voltage (V$_\pi$) of 1.2 V and E-O modulation bandwidth greater than 80 GHz is obtained for a 2-cm-long modulator. By utilizing the slotted slow-wave electrode, TFLN Mach-Zehnder modulators with CMOS-compatible operating voltage and 3-dB modulation bandwidth greater than 100 GHz are potentialized.

In this work, we design, model, and characterize the Bragg grating modulator (BGM) on silicon-rich nitride and thin-film lithium niobate (SRN-TFLN) platform. In particular, the slow-light effect on the electro-optical modulation response is modeled and experimentally validated. The presented modulator shows a 3-dB electro-optical (E-O) bandwidth beyond 40 GHz, which agrees well with the simulation results. High-speed modulation up to 60 Gbps and 70 Gbps are experimentally obtained with extinction ratio (ER) of 4.7 dB and 2.7 dB, respectively. A measured modulation efficiency of 2.47 pm/V is also achieved. With optimized slow-light effect and proper design, the proposed BGM has great potential in high-speed data transmission.

A four-mode (de-)multiplexer with transverse electric field light ( T E 0 − T E 3 ) is experimentally demonstrated on a thin film lithium niobate–silicon rich nitride hybrid platform. Enabled by cascaded asymmetrical directional couplers, a (de-)multiplexer with low insertion loss (0.38 dB to 1.6 dB) and low cross talk ( − 18.46 d B to − 20.43 d B ) is obtained at 1550 nm. All channels have cross talk < − 16 d B from 1480 nm to 1580 nm. The transmission of 4 × 50 Gbps on–off keying signals is experimentally achieved on the proposed (de-)multiplexer. Experimental results show that the proposed (de-)multiplexer is a promising approach to enhance the transmission capacity in thin film lithium niobate based photonics integrated circuits.

A grating coupler on a thin film x -cut lithium niobate–silicon rich nitride hybrid platform is proposed and demonstrated. An inverse taper is applied to suppress higher-order mode excitation. A coupling efficiency of − 5.82 d B and 3 dB bandwidth of 57 nm are obtained near the wavelength of 1550 nm between the standard single-mode fiber (SMF-28) and sub-micrometer waveguides.

TE/TM-pass polarizers based on the lithium niobate–silicon nitride hybrid platform are numerically proposed for the first time, to the best of our knowledge. By utilizing the lateral leakage of a shallowly etched rib waveguide, 1-mm-long TE/TM-pass polarizers with high extinction ratios of 28.72/24.03 dB are obtained. Because of the anisotropy of the lithium niobate, the lateral leakage of TE/TM polarization modes can occur along crystallographic z / y directions, respectively. Such TE/TM-pass polarizers can be integrated in the same wafer.

In this paper, a silicon rich nitride–lithium niobate on insulator hybrid platform with waveguides and several key components is proposed. The propagation loss of the silicon rich nitride–lithium niobate rib-loaded waveguide (300 × 300 nm2) is 0.86 dB/cm at 1550 nm. Passive devices, including adiabatic power splitters, multimode interferometer-based splitters, asymmetrical Mach–Zehnder interferometers, and Bragg grating filters, are fully designed and characterized. Moreover, we report a Mach–Zehnder modulator with high-speed modulation up to 120 GBaud without digital compensation. The electro-optical response with 1 dB roll-off at 40 GHz is obtained, and the 3-dB modulation bandwidth is predicted to be >100 GHz. Hence, the proposed platform enables high-performance passive and active devices with low loss and high integration density, making it a promising candidate for emerging photonics integrated circuits.

A four-channel coarse wavelength division multiplexing (CWDM) (de)multiplexer on a thin film lithium niobate–silicon rich nitride hybrid platform has been designed, fabricated, and experimentally measured. Enabled by cascaded multimode waveguide Bragg gratings, the (de)multiplexer has a box-like spectral response, wide 1-dB bandwidth (10 nm), low excess loss ( < 1.08 d B ), and low channel cross talk ( < − 18 d B ). The central wavelengths of the (de-)multiplexer are 1531/1551/1571/1591 nm, which align to the wavelength grids stipulated by the standard ITU-T G.694.2.

Based on the epsilon-near-zero (ENZ) effect of indium tin oxide (ITO), we numerically demonstrate a high efficiency ITO phase/intensity modulator by exploiting ultra-thin silicon strip waveguide configuration. Heavily n-doped indium tin oxide is used as the semiconductor together with p-doped silicon and hafnium oxide (HfO2) to form a MOS waveguide. Due to the special feature of the ultra-thin silicon waveguide structure, the propagating transverse electric (TE) mode is less confined to the silicon core and penetrates deeper into the cladding layer, which will enhance the interaction between the active material and the optical mode. The combination of the ultra-thin silicon strip waveguide and ITO material exhibits high modulation efficiency together with broad optical bandwidth. When the modulator operates as a phase modulator, the effective refractive index change can reach the value 8:95x10-3 for the light wavelength λ = 1550 nm when the applied voltage is 6 V. Thus, the phase shifter length which can induce a π phase shift is supposed to be only about 97 µm, giving a corresponding VπL of 0.58 V∙mm. The effective index change even keeps > 7:32 x 10-3 with the wavelength increasing from 1300 nm to 1800 nm, indicating the broad modulation bandwidth. Meanwhile, the modulator can also operate as a variable optical attenuator or an intensity modulator. The modulation depth (MD) is about 0.074 dB/µm at 9 V when the wavelength is 1550 nm. This device confirms electrical phase shifting in ITO enabling its use in applications such as compact phase shifters, sensing, and phased array applications for LiDAR.

We propose and demonstrate a Michelson interferometer modulator with integrated Bragg reflectors on a silicon-rich nitride–thin-film lithium niobate hybrid platform. High-reflectivity Bragg reflectors are placed at the ends of both arms, which double the electro-optic (E-O) interaction length and reduce the velocity mismatch between the microwave and optical wave. The presented Michelson interferometer modulator achieves a measured half-wave voltage length product as low as 1.06 V cm and high-speed modulation up to 70 Gbps. A 3-dB E-O bandwidth beyond 40 GHz is also achieved, which is, to the best of our knowledge, the highest modulation bandwidth of Michelson interferometer modulators.

We propose and experimentally demonstrate a passive and compact interleaver on a silicon on insulator (SOI) platform using a ring-assisted asymmetrical Mach–Zehnder interferometer configuration. The wavelength-insensitive couplers, i.e., multimode interference couplers and adiabatic 3-dB couplers, are introduced to eliminate the effect of an unequal splitting ratio and wavelength on crosstalk and the operating spectral range. In addition, there exists an inherent phase shift between the two couplers; the device can be fully passive and works well without additional thermal tuning. In the calculation, the influence of wavelength sensitivity of self-coupling coefficients and couplers on the performance of the interleaver is considered. The experiment shows that, by employing wavelength-insensitive couplers, the operating spectral range of the proposed interleavers was extended to be > 140 n m for all sorts of channel spacing and channel count. The measured free spectral range is 4.6 nm, and the crosstalk is as low as − 46.6 d B for the best case.

This publisher’s note contains a correction to Opt. Lett. 45, 4915 (2020)OPLEDP0146-959210.1364/OL.404197.