Search

All-optical control of silicon photonic devices plays a key role in on-chip all-optical computing, switching and signal processing. However, due to the weak intrinsic nonlinear effects of silicon, current integrated devices are limited by high power consumptions. Here, an all-optical controllable optomechanical microring resonator (OMMR) is proposed and fabricated on the silicon platform. Due to the mechanical Kerr effect induced by the optical gradient force (OGF), we realize seamless wavelength tuning over a range of 2.56 nm which is 61% of the free-spectral range, with a high tuning efficiency of 80 GHz/mW. By controlling the pump power, the OMMR indicates three working regions, which are the cutoff region, amplified region and saturate region. Accordingly, this function is similar to a transistor. Furthermore, the dynamic properties of the OMMR are investigated. By analyzing the dynamic responses, we demonstrate that the OMMR is driven by the OGF, rather than other nonlinear effects. The method simplifies the experimental setup, compared with measuring the intrinsic mechanical frequency of the OMMR. This all-silicon device is energy-efficient and compatible with complementary metal-oxide semiconductor (CMOS) processing. We believe that this work is important for on-chip all-optial signal processing and beneficial to futher studies on integrated optomechanics. [ABSTRACT FROM AUTHOR]

This paper proposes an electronic-photonic converged adaptive-tuning-step (ATS) pipelined time-division-multiplexing (PTDM) scheme to achieve fast wavelength locking of multiple micro-ring resonators (MRRs) using a shared controller without deteriorating the locking accuracy. The ATS technique breaks the trade-off between wavelength tracking speed and locking accuracy. The PTDM control enables controller sharing while maintaining a high loop bandwidth by exploiting the speed mismatch between the heater and the controller. Custom-designed integrated circuits provide interfacing and clocking functions. A hybrid-integrated four-channel prototype of the proposed scheme has demonstrated a record-breaking tracking speed of 180 nm/s with a locking accuracy of about 7 pm and a tuning range of about 9 nm. This scheme could be extended to applications with dozens or even hundreds of MRRs. [ABSTRACT FROM AUTHOR]

A tunable and reconfigurable bandpass microwave photonic filter (MPF) is demanded in scenarios where different center frequencies and bandwidths are required. Here, we propose and demonstrate a silicon-on-insulator (SOI)-based microwave photonic bandpass filter, whose center frequency and bandwidth can be adjusted. The MPF is implemented by using four cascaded microring resonators (MRRs) that fabricated based on SOI wafer. Each MRR combines the design of multi-mode waveguides and tunable coupling regions, thereby exhibiting simultaneous high frequency selectivity and excellent reconfigurability. The center frequency can be tuned by adjusting the resonant wavelengths of the MRRs, and the bandwidth can be reconfigured by adjusting the coupling coefficients as well as the resonant wavelengths of the MRRs. The operation state of each MRR can be monitored and thus the MPF can be adjusted precisely. In the experiment, the bandwidth and center frequency of the MPF are adjusted from 0.7 to 2 GHz and from 5.2 to 35.8 GHz, respectively. During the adjustment, the rejection ratio of the MPF remains above 40 dB. The link performance, including the link gain, noise figure and spurious-free dynamic range, are also charactered. The achieved MPF can be potentially applied to radar, sensor networks, and wireless communications. [ABSTRACT FROM AUTHOR]

Ultrafast measurement ofbroadband radio frequency (RF) spectrum is of great importance in dispersion compensation, signal impairment monitoring and coherence analysis. As an all-optical RF spectrum measuring system, the frequency-domain light intensity spectrum analyzer (f-LISA) maps the RF information into the time domain and realizes the single-shot RF spectrum acquisition. In order to further improve the performance of f-LISA, we investigate theoretically the relationship of resolution and bandwidth with the factors including the spectral width of the probe, the front and output 3rd-order dispersion (TOD). Under the theoretical guidance, 1 nm spectral width of the probe is filtered out to reduce the impact of the front TOD, and the optical phase conjugation is adopted to decrease the output TOD which has a greater impact on f-LISA. The optimized f-LISA achieves the frame rate of 20.6 MHz, the resolution of 1 GHz and the bandwidth of 2.2 THz which is 3 times wider than the original f-LISA, demonstrating better measurement stability and accuracy. Furthermore, the high-speed and broadband RF spectrum analyzer is promising to provide a solution for ultrafast dynamical RF spectrum scenario like terahertz measurement. [ABSTRACT FROM AUTHOR]

This letter proposes a deep learning-based method for wireless communication signal modulation recognition. Modified generalized end-to-end (GE2E) loss is used to train the designed neural network, which can increase the similarity of the feature vectors of the same modulation type and reduce that of different types. The similarities between training samples and centroid vectors are calculated to set the adaptive thresholds for each known modulation type. The experimental results show that the proposed method can reject unknown signals while remaining the recognition quality of known signals, which has higher efficiency and lower complexity than other open set recognition (OSR) algorithms in modulation recognition. [ABSTRACT FROM AUTHOR]

Integrated polarization stabilizers along with corresponding stabilizing algorithms have been investigated for years to tackle the polarization fluctuation issue in polarization dependent systems such as photonics integrated circuits and coherent optical communication systems. Here, we propose and demonstrate a novel integrated polarization stabilizer which is composed of an in-line polarimeter and two cascaded Mach-Zehnder interferometers-based polarization converter, with a footprint of 2.8 mm × 0.8 mm. Benefitting from the integrated in-line polarimeter and two controlling algorithms, namely feed-forward tracking algorithm and feedback tracking algorithm, the stabilizer can track the incoming light with arbitrary state of polarization in one-time manipulation. The whole process consumes about 30 μs, which is approaching the limitation of the response time of the adopted thermal phase shifters, making the proposed device the fastest one with thermal phase shifters on silicon photonics platform. Meanwhile, the incoming light is endlessly tracked in real time and 99% converted to horizontal linear polarized light. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a novel lateral-zigzag PN junction for silicon modulator working in C and O bands. The designed PN junction exhibits characteristics of large bandwidth, high modulation efficiency, and easy fabrication. For demonstration, it is embedded in a 220 nm silicon rib waveguide on a 2 $\mu \text{m}$ thick buried oxide layer to form a micro-ring modulator. The measured 3 dB electro-optic bandwidth of the fabricated modulator is 42 GHz while the resistor-capacitor (RC) bandwidth is measured and calculated to be 174 GHz. Clear and open eye diagrams are obtained for 50 Gb/s non-return zero (NRZ) and 100 Gb/s four-level pulse amplitude modulation (PAM4) signals. The modulation power consumption is only 14 fj/bit. [ABSTRACT FROM AUTHOR]

Terahertz (THz) technology offers multifaceted capabilities and disruptive applications in line-of-sight wireless communication, highly sensitive (bio)sensing, imaging and so on. However, the severe lack of polarization devices comparable to those for other electromagnetic frequencies is impeding moving towards practical applications. Here we demonstrate, for the first time, silicon-based integrated, high polarization extinction ratio, low insertion loss, and compact THz polarization beam splitters (PBSs) fabricated by CMOS-compatible technologies based on dielectric environment variation induced evanescent wave coupling effect. Through comprehensively analyzing working principles of conventional two-waveguide-based PBS, a high-performance three-waveguide PBS is successfully realized. Further optimizing the device parameters and working bandwidth, we achieve an integrated broadband PBS based on cascaded asymmetric directional couplers, whose polarization extinction ratios reach up to 20 dB and 32 dB for transverse electric and transverse magnetic modes, respectively, and their 10-dB bandwidth is 32 GHz for a device length of 15.5 mm. These numbers are the highest in silicon-based integrated THz PBSs so far. We believe our observations provide an effective way for exploring on-chip high-performance THz-PBSs for polarization-diverse systems, accelerating the development and application of on-chip THz photonics. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate an approach to generating reconfigurable linearly chirped microwave waveforms (LCMWs) based on a Fourier domain mode-locked (FDML) optoelectronic oscillator (OEO), in which a tunable and reconfigurable microwave photonic filter (MPF) based on a high-Q microring resonator (MRR) is used for mode selection. The MPF can be electrically tuned to achieve Fourier domain mode-locking by using a micro-heater deposited on the MRR. Adjusting the state of polarization of the optical carrier, the MPF is reconfigured and multi-band and multi-format LCWMs can be generated based on the FDML OEO. In the experiment, a dual-chirp LCMW with a bandwidth of 12 GHz consisting of an up-chirped waveform from 7 to 13 GHz and a down-chirped waveform from 19 to 13 GHz is realized, with a time-bandwidth product (TBWP) as high as 1.004×106. By reconfiguring the MPF, we can also obtain LCMWs with a single chirp at C-band (from 4 to 8 GHz), X-band (from 8 to 12 GHz) and Ku-band (from 13 to 19 GHz), respectively. Further, the bandwidth and center frequency of the LCMWs and the dual-chirp LCMWs can be changed by adjusting the magnitude of the driving signal and the laser wavelength, respectively. This kind of reconfigurable LCMWs can be applied to advanced multi-band radar and wireless communication systems. [ABSTRACT FROM AUTHOR]