Photonic Temporal Differentiator Research Articles

Simple reconfigurable multiport photonic temporal N-differentiator and integrator based on dual-ring coupled Mach–Zehnder interferometer

At present, a high-order, reconfigurable photonic signal processor is very difficult to implement. A simple, reconfigurable photonic N-differentiator and integrator based on a unit of the dual-ring coupled Mach–Zehnder interferometer (DRMZI) is proposed first. The reconfigurability is achieved only by controlling the thermo-optic phase shifter (TO-PS) on the two improved micro-ring resonators. The device presents a wide fine-tunable differentiation order range from 0.2 ≤ N ≤ 1.7 reconfigured as a 2 × 2 differentiator after being optimized the TO-PS and the tunable couplers (TC). If it is reconfigured as an integrator, a first-order photonic temporal integrator with 16.1 GHz 3-dB bandwidth and integration time window 38.4 ps is achieved in our design. The 4 × 4 port DRMZI differential unit can be cascaded into k-stage to realize 0.2 × k ≤ N ≤ 1.7 × k order differential function, theoretically approaching any large order. At the same time, the differential signals can be successfully routed to different output ports by reconfiguring the optical path in the structure. The simulation results have shown that a two-stage 4 × 4 photonic temporal differentiator can perform more than two order differential operations, e.g., N = 2.4. Our research can provide a reference for chip-level large-scale integrated photonic processors.

Subpicosecond flat-top pulse shaping using a hybrid plasmonic microring-based temporal differentiator

Design of a fractional-order photonic temporal differentiator, based on the silicon hybrid plasmonic add-drop microring resonators, is proposed. Because of the strong light confinement in the hybrid plasmonic waveguides, the overall footprint of the differentiator is significantly reduced. The numerical simulation results show that the differentiator can reach considerably wide 3 dB bandwidth of about 2.5 THz (20 nm) with the microring radius of 1.2 μm. It is also shown that the differentiation order and the 3 dB bandwidth of the proposed structure can be tuned in the range of [0.6 1.0] and [1.74 2.5] THz ([14 20] nm), respectively, by modifying the geometrical parameters of the differentiator. Mentioned bandwidth is higher than the previously reported values for microring-based photonic differentiators. Furthermore, the wide bandwidth and the tunable differentiation order of the structure along with its compact footprint make it a promising choice for the processing of ultrashort optical pulses. Generation of short flat-top pulses from input Gaussian pulses is then considered as an example of such applications. It is shown through three-dimensional finite-difference time-domain simulations that the proposed differentiator can be used to generate a flat-top pulse with the flat duration of 330 fs and the FWHM of ∼1 ps, from an ultrashort Gaussian input pulse, with the FWHM of 490 fs.

Silicon-Based Integrated Tunable Fractional Order Photonic Temporal Differentiators

Two integrated fractional-order photonic temporal differentiators based on two Mach–Zehnder interferometer (MZI) structures implemented on a silicon-on-insulator (SOI) platform are designed, fabricated, and experimentally evaluated. The first photonic temporal differentiator employs a multimode interference (MMI) coupler as one of the two 3-dB couplers of the MZI. By changing the polarization state of the input optical signal, the coupling coefficient of the MMI is changed, which leads to the change of the phase shift in the destructive interference wavelength, and a photonic temporal differentiator with a tunable fractional order is implemented. The second photonic temporal differentiator is designed to have two cascaded MZIs, a balanced MZI, and an unbalanced MZI. A phase modulator (PM) is incorporated in one of the two arms of each of the MZIs. The balanced MZI with a PM forms an active tunable coupler, which is used to actively tune the fractional order of the temporal differentiator. The PM in the unbalanced MZI is used to tune the operating wavelength. The two photonic temporal differentiators are designed and fabricated in a CMOS compatible SOI platform, and their performance is evaluated experimentally. The experimental results show that both temporal differentiators can have a tunable fractional order from 0 to 1. In addition, the use of the active temporal differentiator to perform high-speed coding with a data rate of 16 Gb/s is experimentally evaluated.

Reconfigurable photonic temporal differentiator based on a dual-drive Mach-Zehnder modulator.

We propose and demonstrate a reconfigurable photonic temporal differentiator based on a dual drive Mach-Zehnder modulator (DDMZM). The differentiator can be reconfigured to different differentiation types by simply adjusting the bias voltage of DDMZM. Both simulations and experiments are carried out to verify the proposed scheme. In the experiment, a pair of polarity-reversed field differentiation and a pair of polarity-reversed intensity differentiation are successfully generated. The differentiation accuracy and conversion efficiency versus the time delay are also investigated.

Terahertz-bandwidth photonic temporal differentiator based on a silicon-on-isolator directional coupler.

We experimentally demonstrate a terahertz-bandwidth photonic differentiator employing a silicon-on-insulator directional coupler. The integrated waveguide coupler with two identical paralleled strip waveguides achieves a first-order differentiator when full energy coupling is met from one waveguide to another. The integrated waveguide coupler can offer different operation bandwidths by changing the length and gap of the strip waveguides. Due to the large 3 dB bandwidth of the directional coupler, we implement the first differentiator with an operation bandwidth of 1.25 THz. The performance of this photonic differentiator is tested using Gaussian-like pulses with a pulsewidth of 2.8 ps, 4 ps, 6 ps, 8 ps, and 10 ps, respectively. The differentiation processing errors and relative energy efficiency are also discussed. This silicon chip may have potential applications in integrated photonic computing circuits with sub-picosecond pulses.

An ultra-high-speed photonic temporal differentiator using cascaded SOI microring resonators

A high-speed photonic temporal differentiator based on cascaded SOI microring resonators is proposed and experimentally demonstrated in this study. The first-order all-optical differentiation functionality is realized through approaching the critical coupling condition of the cascaded microring resonators. A three-stage double channel side-coupled cascaded microring structure is used to provide wider bandwidth and larger notch depth in its transmission spectrum. The fabricated cascaded SOI microring device is experimentally verified by Gaussian-like pulse trains with a data rate of up to 80 Gbit s−1. Due to the use of cascaded microring resonators, the notch depth in the transmission spectrum is increased from less than 30 dB to larger than 30 dB, thus the quality of the differentiated signal is improved.

Multichannel Arbitrary-Order Photonic Temporal Differentiator for Wavelength-Division-Multiplexed Signal Processing Using a Single Fiber Bragg Grating

A multichannel photonic temporal differentiator implemented based on a single multichannel fiber Bragg grating (FBG) for wavelength-division-multiplexed (WDM) signal processing is proposed for the first time to our knowledge. The multichannel FBG is designed using the discrete layer peeling (DLP) algorithm together with the spatial sampling technique. Specifically, the DLP algorithm is used to design the spectral response of an individual channel, while the spatial sampling is employed to generate a multichannel response. The key feature of the proposed temporal differentiator is that WDM signals at multiple optical wavelengths can be simultaneously processed. Two sampling techniques, the phase-only and the amplitude-only, are employed. The use of the phase-only sampling technique to design a 45-channel first-order and second-order temporal differentiator is performed, and the use of the amplitude sampling technique to design a 3-channel first-order and second-order temporal differentiator is also performed. A proof-of-concept experiment is then carried out. A 3-channel first-order differentiator with a bandwidth of 33.75 GHz and a channel spacing of 100 GHz is fabricated. The use of the fabricated 3-channel FBG to perform first-order temporal differentiation of a 13.2-GHz Gaussian-like optical pulse with different optical carrier wavelength is demonstrated.

Stable all-fiber photonic temporal differentiator using a long-period fiber grating interferometer

A novel configuration of all-fiber photonic temporal differentiator optimized for tens-of-gigahertz processing bandwidth is suggested and experimentally demonstrated. This device covers the gap in terms of processing bandwidth between the two previously-demonstrated all-fiber designs, namely the fiber Bragg grating-based differentiator (<20 GHz) and that based on a uniform long-period fiber grating (>100–200 GHz).