Mingzhi Lu

Second-order bandpass terahertz filter achieved by multilayer complementary metamaterial structures

We propose a multilayer complementary metamaterial structure fabricated on a crystal quartz substrate measuring between 100 and 700 GHz. The concept of a second-order terahertz bandpass filter is realized by this structure, and it offers a superior quality factor, steepness of skirts, and out-of-band rejection. Physical limitations on the quality factor and insertion loss have also been studied, including the skin depth of the metal and the optical phonon resonance in quartz. Based on these factors, a series of higher frequency filters has been designed, and simulation results are presented.

Highly integrated optical heterodyne phase-locked loop with phase/frequency detection.

A highly-integrated optical phase-locked loop with a phase/frequency detector and a single-sideband mixer (SSBM) has been proposed and demonstrated for the first time. A photonic integrated circuit (PIC) has been designed, fabricated and tested, together with an electronic IC (EIC). The PIC integrates a widely-tunable sampled-grating distributed-Bragg-reflector laser, an optical 90 degree hybrid and four high-speed photodetectors on the InGaAsP/InP platform. The EIC adds a single-sideband mixer, and a digital phase/frequency detector, to provide single-sideband heterodyne locking from -9 GHz to 7.5 GHz. The loop bandwith is 400 MHz.

Monolithic Integration of a High-Speed Widely Tunable Optical Coherent Receiver

In this letter, a monolithically integrated widely tunable optical receiver is demonstrated. A sampled-grating DBR (SG-DBR) laser, an optical 90-degree hybrid, four high-speed uni-travelling-carrier photodetectors and microstrip transmission lines are integrated on a single InGaAsP/InP chip. A 42-nm tuning range and a 35-GHz detector bandwidth are achieved. Experiments show real-time reception of 40 Gb/s BPSK data.

40Gbit/s coherent optical receiver using a Costas loop

A highly integrated 40 Gbit/s coherent optical receiver is reported using a Costas loop as a homodyne optical phase locked loop (OPLL). A photonic IC, an electrical IC, and a hybrid loop filter are characterized, and the feedback loop system is fully analyzed to build a stable homodyne OPLL. All components are integrated on a single substrate within the compact size of 10 × 10mm(2), and a 1.1 GHz loop bandwidth and a 120 psloop delay are achieved. The binary phase-shift keying receiver exhibits error-free (BER<10(-12)) up to 35 Gbit/s and BER<10(-7) for 40 Gbit/s with no latency, and consumes less than 3 W power.

An Integrated 40 Gbit/s Optical Costas Receiver

In this paper, a highly-integrated widely-tunable optical homodyne receiver is reported with 40 Gbaud/s data rate. By using photonic and electronic integration, the receiver is realized within a size of 10 × 10 mm2, and the system is very robust and resistive to environmental changes. An integrated photonic coherent receiver circuit is demonstrated with 35 GHz photodetector bandwidth, and the integrated local oscillator (LO) laser covers a 40 nm range. The electronic IC (EIC) has a working frequency up to 50 GHz. The feedback loop is carefully analyzed and designed, and the experimental results show > 1.1 GHz loop bandwidth, which matches the design. The hold-in range is measured to be > 15 GHz. The phase noise of the transmitting laser has been cloned to the LO laser quite well, and both the linewidth measurement and phase noise measurement show no observable cross talk between binary phase shift keying (BPSK) data and the optical phase-locked loop (OPLL). Error free ( bit error rate <; 10-12) is achieved up to 35 Gbit/s. The system consumes 3 Watts of power.

Indium Phosphide Photonic Integrated Circuits for Coherent Optical Links

We demonstrate photonic circuits monolithically integrated on an InP-based platform for use in coherent communication links. We describe a technology platform that allows for the integration of numerous circuit elements. We show examples of an integrated transmitter which offers an on-chip wavelength-division-multiplexing source with a flat gain profile across a 2 THz band and a new device design to provide a flatted gain over a 5 THz band. We show coherent receivers incorporating an integrated widely tunable local oscillator as well as an optical PLL. Finally, we demonstrate a tunable optical bandpass filter for use in analog coherent radio frequency links with a measured spurious-free dynamic range of 86.3 dB-Hz2/3 as well as an improved design to exceed 117 dB-Hz2/3.

An integrated parity-time symmetric wavelength-tunable single-mode microring laser

Mode control in a laser cavity is critical for a stable single-mode operation of a ring laser. In this study we propose and experimentally demonstrate an electrically pumped parity-time (PT)-symmetric microring laser with precise mode control, to achieve wavelength-tunable single-mode lasing with an improved mode suppression ratio. The proposed PT-symmetric laser is implemented based on a photonic integrated circuit consisting of two mutually coupled active microring resonators. By incorporating multiple semiconductor optical amplifiers in the microring resonators, the PT-symmetry condition can be achieved by a precise manipulation of the interplay between the gain and loss in the two microring resonators, and the incorporation of phase modulators in the microring resonators enables continuous wavelength tuning. Single-mode lasing at 1,554.148 nm with a sidemode suppression ratio exceeding 36 dB is demonstrated and the lasing wavelength is continuously tunable from 1,553.800 to 1,554.020 nm.

A 1–20-GHz All-Digital InP HBT Optical Wavelength Synthesis IC

An integrated circuit (IC) for heterodyne optical phase locking in a 1-20-GHz offset range is hereby reported. The IC, implemented in a 500-nm InP HBT process, contains an emitter coupled logic digital single-sideband mixer to provide phase locking at a ± 20-GHz offset frequency, and a wideband phase-frequency detector designed to provide loop acquisition up to ±40-GHz initial frequency offset. The all-digital IC design has phase-frequency detection gain independent of IC process parameters or optical signal levels, and provides a wide offset locking range. A 100-ps delay decreases the overall loop delay, making wideband loop filter design possible. In addition, a medium-scale high-frequency logic design methodology is presented and fully discussed.

First Monolithically Integrated Dual-Pumped Phase-Sensitive Amplifier Chip Based on a Saturated Semiconductor Optical Amplifier

For the first time, a monolithically integrated photonic phase-sensitive amplification chip is fabricated and demonstrated based on an InP/InGaAsP platform. Different semiconductor optical amplifiers have been fabricated as well for characterization. On the chip, two tunable laser pumps that are coherently injection-locked, respectively, from two first-order sidebands of an externally modulated tone are generated to enable signal-degenerate dual-pumped phase-sensitive amplification in a saturated semiconductor optical amplifier. Experiments on different chips are conducted to successfully demonstrate phase-sensitive amplification with approximately 6.3 and 7.8 dB extinction of phase-sensitive on-chip gain. Theoretical simulations are performed and agree well with experimental results. The additive noise properties of the phase-sensitive amplification chip are also investigated.

A 1–20 GHz InP HBT phase-lock-loop IC for optical wavelength synthesis

We report a PLL IC for locking, at a controlled frequency offset between 1 and 20 GHz, the optical phase and optical frequency of a slave semiconductor laser to that of a reference semiconductor laser. The IC, implemented in a 500 nm InP HBT process, contains an ECL digital single-sideband mixer to provide phase-locking at a +/− 20 GHz offset frequency, and also contains a wideband phase-frequency detector to provide loop acquisition given up to +/−40 GHz initial frequency offset.