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A multiport thermo-optic switch based on parallel polymer waveguides and microheater array is proposed. The basic unit is a $1\times3$ switch for Up Transfer, Isolation, and Down Transfer operations. By introducing refractive index perturbation along the selected waveguides through microheaters, the Transfer /Isolation condition can be switched locally, and light is then steered into different paths. A $1\times5$ switch is demonstrated experimentally as an example. Colorless ( $1.50~\mu \text{m}$ to $1.62~\mu \text{m}$ ) and polarization independent operation is achieved with crosstalk suppression ratio larger than 10 dB, which can be further optimized. The design requires less waveguides and tuning sections than conventional Mach-Zehnder interferometer-based switches. 6 microheaters are placed but only 3 need to be powered on simultaneously to reach any of the 5 output ports. The maximal heater power is 33.8 mW over a coupling length of $1331.6~\mu \text{m}$ . This design can easily scale up to form an arbitrary cascaded M $\times1$ and $1\times $ N switch network for high-density photonic integration.

In this article, we demonstrate a push-pull silicon dual-ring modulator based on two cascaded rings which are coupled with each other through two parallel bus waveguides. In the transmission spectrum of the modulator, a narrow transparency peak exists in the center of the broad dip based on the electromagnetically induced transparency (EIT)-like effect. Benefiting from both the EIT-like effect and push-pull drive configuration, a low insertion loss (IL) of 1.4 dB and an extinction ratio (ER) over 6.4 dB are obtained at a bit rate of 10 Gb/s with a peak-to-peak driving voltage (Vpp) of 5 V. The corresponding maximum optical modulation amplitude (OMA) is 0.56, which is almost twice that of a single micro-ring modulator with the same driving voltage. Moreover, the maximum OMA is 0.47 at 20 Gb/s, which is 81% larger than that of a single micro-ring modulator.

We propose and experimentally demonstrate a microwave photonic phase shifter based on a tunable silicon photonic interleaver. This device consists of a microring resonator, a tunable interleaver, and a $2\,\times \,1$ multimode interferometer (MMI). By thermally tuning the interleaver, a linear phase shift of 188° is realized with a linearity of 0.08 and a radio-frequency (RF) power variation within 1 dB for a 40-GHz signal.

We present the design and experimental demonstration of a compact tunable silicon photonic interleaver with a wide spectral range. The interleaver consists of an interfering loop containing a Fabry–Perot cavity formed by two Sagnac loops. The transmission coefficients of the directional couplers are calculated based on the maximally flat criterion. The impacts of the transmission coefficient variations on the extinction ratio and filter sharpness are investigated. The wavelength dependences of the directional couplers are analyzed to increase the spectral range of the interleaver. The device was fabricated on a silicon-on-insulator platform. The spectral ranges of the measured transmission and reflection spectra are increased to 60 nm. By thermal tuning the waveguide connecting the two Sagnac loops, the central wavelength can be shifted over one free spectral range with a wavelength-tuning efficiency of ∼0.08 nm/mW.

We demonstrate a real-time holographic display using quantum-dot doped liquid crystal with a build-up time of several to tens of milliseconds, and the maximum diffraction efficiency is measured up to 30%. Holographic videos of red, green, and blue colors at a refresh rate of 60 Hz are realized. The dependences of response time on the recording intensity, applied voltage, and grating period are investigated.

We propose and experimentally demonstrate an on-chip all-optical differential-equation solver capable of solving second-order ordinary differential equations (ODEs) characterizing continuous-time linear time-invariant systems. The photonic device is implemented by a self-coupled microresonator on a silicon-on-insulator platform with mutual coupling between the cavity modes. Owing to the mutual mode coupling within the same resonant cavity, the resonance wavelengths induced by different cavity modes are self-aligned, thus avoiding precise wavelength alignment and unequal thermal wavelength drifts as in the case of cascaded resonators. By changing the mutual mode coupling strength, the proposed device can be used to solve second-order ODEs with tunable coefficients. System demonstration using the fabricated device is carried out for 10-Gb/s optical Gaussian and super-Gaussian input pulses. The experimental results are in good agreement with theoretical predictions of the solutions, which verify the feasibility of the fabricated device as a tunable second-order photonic ODE solver.

We propose and experimentally demonstrate a reconfigurable ultrawideband (UWB) pulse generation scheme by using a dual-drive Mach-Zehnder modulator (DDMZM). In the proposed method, two phase modulators of the DDMZM are respectively driven by properly designed electrical signals. By carefully setting the parameters of the two electrical signals and the bias voltage of the DDMZM, different UWB pulses can be achieved at the interference output of the DDMZM. A proof-of-concept experiment verifies the feasibility of the proposed method. Photonic generations of UWB monocycle, doublet, triplet, and quintuple pulses have been successfully demonstrated, with central frequencies of 4.69, 4.69, 5.47, and 6.25 GHz and fractional bandwidths of 150%, 133%, 186%, and 75%, respectively.

We propose and experimentally demonstrate a new method to generate a 3-D ultrawideband (UWB) signal by utilizing a dual-drive Mach-Zehnder modulator (DDMZM). Three degrees of freedom of the generated 3-D UWB signal are pulse position, pulse phase, and pulse amplitude. In this scheme, each radio frequency (RF) port of the DDMZM is modulated by a combination of two encoded signals with different amplitudes. By properly adjusting the amplitudes of the encoded signals and the bias voltages of the two RF ports, a 5-Gb/s 3-D UWB signal with a central frequency of 3.5 GHz and a 10-dB fractional bandwidth of 163% is successfully generated by using only a single DDMZM.

In this paper, we propose and demonstrate an all-optical second-order differentiator based on a two-stage self-coupled optical waveguide on a silicon-on-insulator platform. The transmission spectrum of the fabricated device has a parabola-like filtering notch with a 3-dB bandwidth of up to ~ 100 GHz and a depth of ~ 12 dB. Experiments are carried out for 10-, 20-, and 40-Gb/s optical time-domain multiplexing (OTDM) picosecond pulse trains, and the second-order differentiations are achieved using the fabricated device.

We propose and demonstrate a nested configuration of a silicon microring resonator possessing multiple coupling regimes in one passive device. For different resonance notches of the transmission intensity spectrum, diverse notch depths and bandwidths owing to multiple coupling regimes are designed and experimentally achieved. The phase response of the proposed configuration is also investigated. Experimental observation of fast and slow lights at different resonance wavelengths further verifies the realization of multiple coupling regimes.

We propose and experimentally demonstrate a new scheme to support an all-optical virtual private network (VPN) in orthogonal frequency-division multiple-access passive optical networks (OFDMA PONs). In our scheme, VPN communications among optical network units (ONUs) are concurrent, where each ONU can simultaneously transmit/receive different VPN traffic to/from other ONUs. Therefore, VPN communications between any two ONUs can be achieved at any time. The bit rates of VPN traffic can be also flexibly adjusted by using dynamic OFDM subcarrier-allocation technique. The proposed scheme is experimentally demonstrated with 5-Gb/s downlink, 2-Gb/s uplink, and 2-Gb/s VPN OFDM signals. Error-free performances are obtained for all these signals after 25-km standard single-mode fiber (SSMF) transmission.

We experimentally demonstrate a push-pull optical nonreciprocal transmission (ONT) mechanism induced by thermo-optic effect in cascaded silicon microring resonators (MRRs). A nonreciprocal extinction ratio of up to 27 dB and an operation bandwidth larger than 0.15 nm are achieved in the proposed ONT system. The device can operate with a resonance mismatch between the two cascaded MRRs from 0.14 nm to 0.55 nm. The proposed ONT device could potentially find applications in optical diodes and bidirectional control of light in future on-chip all-optical information processing systems.