Query: MZM

title: Photonic Generation and Transmission of Linearly Chirped Microwave Waveform With Increased Time Bandwidth Product
abstract: Photonic generation and transmission of linearly chirped microwave waveform with the increased time bandwidth product (TBWP) is proposed and demonstrated by phase encoding and splitting parabolic waveform. In the approach, dual polarization Mach Zehnder modulator (DPol MZM) along with polarization controller (PC) is employed to generate two orthogonally polarized wavelengths, and polarization modulator is driven by a parabolic signal. After splitting parabolic waveform and convolving with a binary pseudo random sequence, chirped microwave waveform with high bandwidth and large temporal duration is generated, corresponding to an improved TBWP. Dispersion induced power fading can be effectively avoided in the approach, and chirped signal with constant initial phase can be achieved by adjusting the PC. The proposed approach is verified by simulations. Linearly chirped microwave waveform with the central frequency of 40 GHz, bandwidth of 12.5 GHz, and TBWP of 20160 is generated. RF spurious suppression ratios of the generated signal are investigated, and pulse compression performances are also analyzed. The system features filter free, high tunability, compact structure, and large TBWP, which has potential application in the modern radar system.

title: Photonic approach for simultaneous measurements of Doppler frequency shift and angle of arrival of microwave signals.
abstract: A photonic method used to simultaneously measure the Doppler frequency shift (DFS) and angle of arrival (AOA) of microwave signals is proposed and experimentally demonstrated. At the remote antenna unit (RAU) the local oscillator (LO) signal and two echo signals are applied to a phase modulator (PM) and a polarization division multiplexed Mach Zehnder modulator (PDM MZM) respectively. After transmission over a fiber link, the DFS and AOA parameters can be obtained by processing the two low frequency electrical signals at the central office (CO) Experimental results show that the DFS between 100 kHz with 5 x 10 3 Hz error and the AOA from 1.82deg to 90deg with <0.85deg error at 10 GHz are obtained over a 10 km single mode fiber (SMF) transmission. Moreover, the DFS direction can also be distinguished by comparing the phase difference of two electrical signals.

title: A Guide for Material and Design Choices for Electro Optic Modulators
abstract: Here we discuss a) fundamental performance vectors of electro optic modulators, and b) showcase recent development of heterogeneous integrated emerging EO materials into Si photonics to include an ITO based MZM, a Graphene hybrid plasmon and the first TMD MRR modulator.

title: Filter free image reject microwave photonic downconverter based on cascaded modulators.
abstract: As essential equipment of the receiver, a novel filter free image reject mixer based on a Mach Zehnder modulator (MZM) and a polarization division multiplexing Mach Zehnder modulator (PDM MZM) is proposed and experimentally demonstrated in this paper. The received radio frequency signal is applied to the MZM, and quadrature local oscillator signals are sent to the PDM MZM, which includes two submodulators in parallel. After a polarization controller and a polarization beam splitter, quadrature intermediate frequency (IF) signals are obtained by two photodetectors. Image rejection is implemented by combining quadrature IF signals via an electrical 90deg hybrid coupler. The scheme uses no filter, so the working frequency can be widely tuned and effective spectrum utilization is achieved. Experimental results verify that image rejection ratios can reach 50 dB. Moreover, the variation of the conversion gain is lower than 2 dB.

title: Scalable Quantum Integrated Circuits on Superconducting Two Dimensional Electron Gas Platform.
abstract: To form a coherent quantum transport in hybrid superconductor semiconductor (S Sm) junctions, the formation of a homogeneous and barrier free interface between two different materials is necessary. The S Sm junction with high interface transparency will then facilitate the observation of the induced hard superconducting gap, which is the key requirement to access the topological phases (TPs) and observation of exotic quasiparticles such as Majorana zero modes (MZM) in hybrid systems. A material platform that can support observation of TPs and allows the realization of complex and branched geometries is therefore highly demanding in quantum processing and computing science and technology. Here, we introduce a two dimensional material system and study the proximity induced superconductivity in semiconducting two dimensional electron gas (2DEG) that is the basis of a hybrid quantum integrated circuit (QIC) The 2DEG is a 30 nm thick In0.75Ga0.25As quantum well that is buried between two In0.75Al0.25As barriers in a heterostructure. Niobium (Nb) films are used as the superconducting electrodes to form Nb In0.75Ga0.25As Nb Josephson junctions (JJs) that are symmetric, planar and ballistic. Two different approaches were used to form the JJs and QICs. The long junctions were fabricated photolithographically, but e beam lithography was used for short junctions' fabrication. The coherent quantum transport measurements as a function of temperature in the presence/absence of magnetic field B are discussed. In both device fabrication approaches, the proximity induced superconducting properties were observed in the In0.75Ga0.25As 2DEG. It was found that e beam lithographically patterned JJs of shorter lengths result in observation of induced superconducting gap at much higher temperature ranges. The results that are reproducible and clean suggesting that the hybrid 2D JJs and QICs based on In0.75Ga0.25As quantum wells could be a promising material platform to realize the real complex and scalable electronic and photonic quantum circuitry and devices.

title: Phase coded Brillouin optical correlation domain analysis with 2 mm resolution based on phase shift keying.
abstract: We report a phase coded Brillouin optical correlation domain analysis (BOCDA) based on phase shift keying (PSK) in which the pseudo random binary sequence (PRBS) phase coding is realized using a Mach Zehnder modulator (MZM) Unlike the conventional phase coded BOCDA using a phase modulator, which suffers from the non rectangular transition in the encoded phase, the PSK can realize perfect phase switches between 0 and p with zero width edges. It is not sensitive to the bandwidth of the modulator and the power of the radio frequency modulation signal. Numerical simulations and experimental results prove that it can effectively suppress the Brillouin amplification in the off peak positions. In experiment, a 2 mm spatial resolution sensing is realized using only a 20 GHz bandwidth MZM.

title: Photonic assisted wideband frequency downconverter with self interference cancellation and image rejection.
abstract: A photonic assisted wideband frequency downconverter with self interference cancellation and image rejection for in band full duplex radio over fiber systems based on a dual polarization quadrature phase shift keying (DP QPSK) modulator is proposed. The upper dual parallel Mach Zehnder modulator (DP MZM) of the DP QPSK modulator is used to cancel the self interference directly in the optical domain and generate two first order optical sidebands of the desired received radio frequency (RF) signal. The lower DP MZM generates two optical sidebands of the local oscillator signal with the optical carrier suppressed via properly biasing the modulator. The optical signals generated from the two DP MZMs are combined, and then the upper and lower optical sidebands of the combined signal are separated by a wavelength division multiplexer (WDM) The two outputs from the WDM are detected by two photodetectors and then combined at a 90deg hybrid coupler to achieve frequency downconversion and image rejection. A simulation is performed. A quadrature phase shift keying (QPSK) modulated RF signal is successfully downconverted to a 1 GHz intermediate frequency signal with self interference and image frequency cancelled. The performance of the frequency downconverter is also evaluated.

title: Total Degradation of a DVB S2 Satellite System with Analog Transparent Optical Feeder Link
abstract: This paper studies the End to End (E2E) performance of a High Throughput Satellite (HTS) system that utilizes a transparent (non regenerative) optical feeder link to transport the DVB S2 signals associated with the large number of spot beams in the radio access link. Two main sources of non linearity are considered to characterize the effect that the satellite forward link has in the DVB S2 signal, namely the optical Mach Zehnder Modulator (MZM) in the gateway and the High Power Amplifier (HPA) in the satellite. Digital Pre Distortion (DPD) and linear equalization are also implemented to mitigate the impact of the non linear distortion and the inter symbol interference on the Packet Error Rate (PER) of the received DVB S2 signal. The performance analysis is carried out using the Total Degradation (TD) as performance indicator. As expected, the Input Back Off (IBO) of the HPA and the modulation index of the MZM should be jointly optimized according to the DVB S2 MODCOD that is selected for transmission. Therefore, the stronger is the Forward Error Correction (FEC) code that is used, the lower is the IBO and the higher is the modulation index that can be utilized to minimize the impact of non linearities in the E2E performance.

title: Silicon dual series Mach Zehnder modulator with high linearity.
abstract: In this Letter, we demonstrate a highly linear silicon modulator based on the dual series Mach Zehnder modulator (MZM) architecture. The two sub MZMs are biased at quadrature points of opposite polarities. A proper power splitting ratio of the driving RF signal on the two sub MZMs enables the suppression of the third order intermodulation distortion (IMD3) The spurious free dynamic ranges (SFDRs) for IMD3 are 109.5/100.5 dB*Hz2/3 at 1/10 GHz. In contrast, the reference single MZM on the same chip exhibits SFDRs of 95.2/86.8 dB*Hz2/3 at 1/10 GHz at its optimal reverse bias voltage.

title: Photonic generation of background free binary and quaternary phase coded microwave pulses based on vector sum.
abstract: A photonic microwave phase coded pulse generator is proposed and experimentally demonstrated based on the principle of vector sum. The key component of the proposed pulse generator is an integrated polarization division multiplexing Mach Zehnder modulator (PDM MZM) and a 90deg hybrid coupler. By properly setting the data sequences applied to the specially biased PDM MZM, binary and quaternary phase coded microwave pulses (PCMPs) that are free from the background signals can be generated. Since no filters and polarization adjustment are involved, the proposed pulse generator is characterized by a simple structure, low loss, flexible frequency tunability and high long term stability. The experimental results show that background free 4 Gb/s Barker and Frank PCMPs at 18 GHz and 2 Gb/s Barker and Frank PCMPs at 24 GHz are successfully generated. The calculated pulse compression ratio and peak to side lobe ratio are in good agreement with the theoretical values.