Photonic Frequency Up-conversion Research Articles

Multi-Functional Microwave Photonic Radar System for Simultaneous Distance and Velocity Measurement and High-Resolution Microwave Imaging

A photonic-assisted multi-functional radar system for simultaneous distance and velocity measurement and high-resolution microwave imaging is proposed and experimentally demonstrated by using a composite transmitted microwave signal of a single-chirped linearly frequency-modulated (LFM) signal and a single-tone microwave signal. In the system, the transmitted signal is generated via photonic frequency up-conversion based on a single integrated dual-polarization dual-parallel Mach-Zehnder modulator (DPol-DPMZM), while the echo signals scattered from the target are de-chirped to two low-frequency signals using a microwave photonic frequency mixer. By using the two low-frequency de-chirped signals, the real-time distance and radial velocity of the moving target can be measured accurately according to the round-trip time of the echo signal and its Doppler frequency shift. Compared with the previously reported distance and velocity measurement methods, where two LFM signals with opposite chirps are used, these parameters can be obtained using only a single-chirped LFM signal and a single-tone microwave signal. Meanwhile, high-resolution inverse synthetic aperture radar (ISAR) imaging can also be realized using ISAR imaging algorithm. An experiment is performed to verify the proposed multi-functional microwave photonic radar system. An up-chirped LFM signal from 8.5 to 12.5 GHz and an 8.0 GHz single-tone microwave signal are used as the transmitted signal. The results show that the absolute measurement errors of distance and radial velocity are less than 5.9 cm and 2.8 cm/s, respectively. ISAR imaging results are also demonstrated, which proves the high-resolution and real-time ISAR imaging ability of the proposed system.

Asymmetric dual-SSB modulation for photonic co-frequency mm-wave signals generation and DSP-free receiver.

An asymmetric dual-single-sideband (SSB) modulation scheme for photonic co-frequency millimeter (mm)-wave signals generation and digital signal processing (DSP)-free receiver is experimentally demonstrated for the first time, to the best of our knowledge. To effectively avoid the sideband crosstalk in the traditional symmetric dual-SSB modulation scheme, not only two vector-modulated signals but also two unmodulated sidebands are modulated on the two asymmetric sides of an optical carrier in this scheme. An optical delay line interferometer could easily separate these two asymmetric dual-SSB signals simultaneously in the receiver, and thus the photonic frequency up-conversion is realized. Besides, this scheme is free of dispersion-induced RF power fading thanks to the SSB modulation. By this means, no digital compensation algorithms such as carrier phase recovery, fiber dispersion compensation, and channel equalization are required, contributing to the DSP-free receiver. In our experiment, two 32 GHz 3.2 Gb/s 16-ary quadrature amplitude modulation mm-wave signals are produced using two RF signals with the carrier frequencies of 12 GHz and 20 GHz. The error vector magnitude (EVM) performances of these two mm-wave signals after 25.5 km standard single-mode fiber transmission are better than 3rd Generation Partnership Project requirements without using any digital compensation algorithms.

Tunable Photonic Microwave Up-Converter Using Opto-Electronic Oscillator Based on Monolithic Integrated Three-Section Laser

A tunable photonic microwave frequency up-conversion scheme using opto-electronic oscillator (OEO) based on a monolithic integrated three-section laser without any electro-optic modulator (EOM) or filter is proposed. By adjusting the monolithic integrated three-section laser to operate in the period-one (P1) dynamical state, the signal carrier frequency up-converted from the intermediate frequency (IF) to the frequency at the difference and the summation between the oscillation frequency of OEO and IF can be realized. The tunability of the up-converted frequency can also be greatly guaranteed just by altering the control currents of the monolithic integrated three-section laser induced P1 frequency. In this paper, an IF of 2 GHz with 10 Msymbol/s 16-QAM signals is successfully up-converted to 16 GHz and 20 GHz simultaneously. The up-converted frequencies can be tuned from 16 GHz/20 GHz to 19 GHz/23 GHz, and the error vector magnitudes (EVMs) of all those up-converted signals satisfy the limitation in satellite communication.

Reconfigurable microwave photonic frequency upconverter with local oscillator doubling or local oscillator quadrupling

A reconfigurable microwave photonic frequency upconverter with local oscillator (LO) doubling or LO quadrupling is proposed based on two cascaded dual-parallel Mach–Zehnder modulators (DPMZMs) and a fiber Bragg grating (FBG) with a wide bandwidth (0.4 nm). The first DPMZM is used to generate the ±1st-order or ±2nd-order sidebands of the LO signal. The FBG is inserted to separate the positive and negative sidebands. Only the transmitted LO sideband is sent to the second DPMZM, and the carrier-suppressed single-sideband (CS-SSB) modulation of the intermediate frequency (IF) signal is realized by using an electrical 90 deg hybrid coupler. The reflected LO sideband via FBG and the −1st-order IF sideband are combined. Then, the upconverted signal with the frequency of 2ωLO + ωIF or 4ωLO + ωIF can be generated by a photodetector. The experimental results show that the spur suppression ratios of the upconverter with LO doubling and quadrupling are 21.3 and 11.3 dB, respectively. The proposed approach greatly reduces the frequency requirement of the LO signal. The purity of electrical spectrum is largely improved in both the LO doubling and LO quadrupling upconversion benefiting from the CS-SSB modulation. Furthermore, these two upconversion modes can be easily switched by tuning the DC biases of the first DPMZM.

Microwave photonic frequency up-converter with LO doubling based on carrier suppression single-sideband modulation

Frequency up-converter as an essential component of the transmitter, which is used to implement the frequency up-conversion by mixing a low-frequency intermediate frequency (IF) signal with a local oscillator (LO) signal. However, only the 1st-order sideband of the LO signal and the IF signal are used in the tradtioanal microwave photonic up-converser, thus the frequency of the up-conversion signal is <i>ω</i><sub>LO</sub> + <i>ω</i><sub>IF</sub>. In this case, an LO with a higher frequency is needed for generating a high-frequency up-converted signal. In order to reduce the frequency requirement of the LO signal, the high-order LO singals or secondary modulation can be used to achieve high-frequency up-conversion. A microwave photonic up-converter with LO doubling based on carrier suppressing single-sideband modulation is proposed based on the cascaded structure of a Mach-Zehnder modulator (MZM) and a dual-parallel Mach-Zehnder modulator (DPMZM). The MZM is driven by an LO signal biased at the minimum transmission point for carrier suppressing double-sideband (CS-DSB) modulation. A fiber Bragg grating (FBG) is used to separate the +1st-order from －1st-order of the LO signal. The －1st-order of LO signal is then sent to a DPMZM for the secondary modulation, and the carrier suppressing single-sideband (CS-SSB) modulation is realized in order to generate the －1st-order of the IF signal by using an electrical 90° hybrid coupler. The modulated IF signal is then combined with the +1st-order LO signal reflected by the FBG and sent into the photodetector (PD) to implement the photoelectric detection. The upconverted signal with a frequency of 2<i>ω</i><sub>LO</sub> + <i>ω</i><sub>IF</sub> can be detected by a PD. The experimental results show that the spur suppression ratio of the optical spectrum and the up-converter signal reach 22.5 dB and 23.6 dB, respectively. The spurious-free dynamic range of the system is 96.1 dB·Hz<sup>2/3</sup>. The proposed system can effectively reduce the frequency requirement of LO signal, and the purity of the electrical spectrum is largely improved which benefits from the CS-SSB modulation. The proposed microwave photonic up-converter provides an effective way for high-frequency emissions in systems such as radio-over-fiber and optically controlled phased array radar.

Efficiency enhancement for the orbital angular momentum photon quantum interface via single photon frequency upconversion

As the application of orbital angular momentum (OAM) of photon quantum in quantum communication, the OAM photon quantum interface for the transmission wavelength from the telecom communication quantum information storage in visible regime is required. Here we demonstrate the efficiency enhancement for the OAM photon quantum interface based on the frequency upconversion from telecom wavelength to visible regime by sum-frequency generation. The infrared photons at 1 558 nm carrying different OAM values could be converted to the visible regime at 622.2 nm with the optimal efficiency via adjusting the pump beam waist radius and intensity.

Geometry-dependent anti-Stokes SERS radiation patterns from gold nanorod dimers

The geometry of individual plasmonic nanostructures and their collective arrangement plays a critical role in electromagnetic enhancement of surface-enhanced Raman scattering (SERS). Concomitantly, the same attributes also have a direct implication on plasmon resonance line-shapes that further affect the far-field radiation pattern of SERS in Rayleigh, Stokes and anti-Stokes spectral regimes. Here we numerically show how Fano-type plasmon resonance lineshapes in certain geometrical configurations of gold nanorod dimers can selectively influence the far-field radiation pattern in the anti-Stokes spectral region of SERS. We explored a variety of dimer angles (0° to 180°) between the gold nanorods, and compared their far-field radiation patterns in the anti-Stokes, Rayleigh and Stokes regions of their plasmon resonance. We found that angles 30° to 60° exhibited greater in-plane forward-to-backward intensity ratios in the anti-Stokes region, compared to other configurations. The results discussed herein highlight a three-way connection between the geometrical arrangement of plasmonic nanostructures, Fano-type lineshapes and far-field radiation patterns in SERS, especially in the anti-Stokes region. Our work will have implications not only in designing optical antennas for linear and nonlinear Raman scattering, but also in creating directional light sources based on nonlinear optical processes such as two-photon fluorescence and photon frequency upconversion.

Broadband photonic single sideband frequency up-converter based on the cross polarization modulation effect in a semiconductor optical amplifier for radio-over-fiber systems

A broadband photonic single sideband (SSB) frequency up-converter based on the cross polarization modulation (XPolM) effect in a semiconductor optical amplifier (SOA) is proposed and experimentally demonstrated. An optical radio frequency (RF) signal in the form of an optical single sideband (OSSB) is generated by the photonic SSB frequency up-converter to solve the power fading problem caused by fiber chromatic dispersion. The generated OSSB RF signal has almost identical optical carrier power and optical sideband power. This SSB frequency up-conversion scheme shows an almost flat electrical RF power response as a function of the RF frequency in a range from 31 GHz to 75 GHz after 40 km single mode fiber (SMF) transmission. The photonic SSB frequency up-conversion technique shows negligible phase noise degradation. The phase noise of the up-converted RF signal at 49 GHz for an offset of 10 kHz is -93.17 dBc/Hz. Linearity analysis shows that the photonic SSB frequency up-converter has a spurious free dynamic range (SFDR) value of 79.51 dB · Hz(2/3).

Simple frequency up-conversion based on nonlinear photodetection scheme of PD in direct modulation radio over fiber system

Abstract This paper presents a simple photonic frequency up-conversion system based on direct modulation radio over fiber (RoF) link which employs optical-microwave double-mixing scheme with a high-speed photodetector (PD). With this up-conversion technique, an intermediate frequency (IF) signal of 500 MHz carrying 40 Mbps 16-quadrature-amplitude-modulation (16-QAM) vector signal is up-converted to 16 GHz in a remote antenna unit via 25-km standard single-mode fiber (SMF) transmission. The received 16 GHz radio frequency (RF) signal is demodulated successfully with the error vector magnitude (EVM) of 7.5% rms. The direct modulation up-converting system provides a sufficiently large spurious free dynamic range of 90 dB·Hz 2/3 . The proposed architecture exhibits the advantages of cost-efficiency, system operation efficiency and reliability.

Local Oscillator Free Frequency Up-Conversion at Millimeter-Wave Band

We have demonstrated all-optical frequency upconversion at millimeter-wave band without using local oscillators. By launching a low bit rate signal into a Fabry-Perot laser diode (FP-LD), a microwave subcarrier is generated based on the four wavelength mixing and injection mode locking. Due to the dynamic charge carrier density response during the injection locking, the wavelength of the leading part of the subcarrier will be red-shifted while that of the falling part will be blue-shifted. By compensating the generated chirp with a suitable negative dispersion device, the time-domain pulses will be compressed and the second harmonic of the subcarrier will be generated. A polarization interferometer is used to further suppress the foundational frequency. In our experiment, a subcarrier of 30.8 and 34.8 GHz is obtained by launching a 2.5-Gb/s NRZ signal into the FP-LD. We also show that the photonic frequency upconversion can go up to ~60 GHz with the proposed scheme.

Photonic frequency upconversion technique using electro-absorption modulator for radio-over-fibre applications

A photonic frequency upconverter utilising an electro-absorption modulator has been experimentally demonstrated for radio-over-fibre applications. Using the upconverter, an optical radio frequency (RF) signal having RF frequencies of 19.5 and 28.5 GHz was generated by mixing a 4.5 GHz optical intermediate frequency signal with a 24 GHz electrical local oscillator signal. The compact photonic frequency upconverter requires no DC bias controller and showed high linearity and polarisation immunity. The measured spurious free dynamic range was 95.4 dB·Hz2/3.

EAM-SOA millimeter-wave frequency up-converter for radio-over-fiber applications

We present an optical scheme for photonic frequency up-conversion at the millimeter-wave bands based on Semiconductor Optical Amplifier. The proposed scheme modulates the bias current with the Intermediate Frequency in order to achieve frequency mixing of an incoming optical signal modulated with the Local Oscillator. Theory indicates that the proposed scheme supports data bandwidths in the tens of GHz for LO values above 10 GHz. This scheme allows for photonic integration of the considered optical devices. A laboratory demonstration of the scheme for up-conversion to the 40 GHz band, using narrow-band IF signals, showed relatively low thresholds for the optical input power and bias current level to achieve error free operation: − 14.5 dBm 100 mA for a 64-QAM signal. Spurious-Free Dynamic Range showed an acceptable performance, with a linearity about 52.5 dB·Hz 2/3 for an optical input power of − 6 dBm.

Simultaneous Multichannel Photonic Up-Conversion Based on Nonlinear Polarization Rotation of an SOA for Radio-Over-Fiber Systems

A photonic frequency up-conversion scheme based on the nonlinear polarization rotation (NPR) arising in a semiconductor optical amplifier for wavelength-division-multiplexing (WDM) baseband signals is proposed and experimentally demonstrated. Error-free simultaneous up-conversion of 4 times 2.5 Gb/s WDM baseband channels with a 20-GHz local oscillator signal is experimentally demonstrated in the whole C-band. Compared with the cross-gain-modulation-based scheme, the proposed scheme is found to be almost independent of the wavelength separation between the probe and pump signals. Both the radio-frequency spectrum and the bit-error-ratio performance after electrical down-conversion have shown low distortion induced by the optical NPR-based up-conversion.

Application of an electroabsorption modulator in radio-over-fiber networks [Invited

A 60⁢ GHz radio-over-fiber (RoF) network using an electroabsorption modulator (EAM) is presented. A photonic frequency upconversion technique that utilizes the wavelength conversion process in the EAM is adopted for seamless integration of optical and wireless networks. The transmission characteristics of the quadrature amplitude modulation (QAM) coded data signal over the 60⁢ GHz photonic-wireless link, which comprises the 50⁢ km optical fiber transmission between the central station and the base station (BS) and the aerial transmission between the BS and the customer unit using horn antennas, are investigated by measuring the error vector magnitude (EVM) and its dependence on the EAM bias voltage. Optimized EVM values of 3.8% and 3.9% are obtained for 64-QAM and 16-QAM at an EAM bias of −0.8 V, respectively.

GaN/AlGaN dual-band infrared detection and photon frequency upconversion

A detailed investigation on dual-band （mid- and far-） infrared detection and photon frequency upconversion in GaN/AlGaN heterojunction structures is carried out. We deduce the Al composition in intrinsic AlGaN barrier layer through photoluminescence spectroscopy, and evaluate the conduction bandgap interfacial workfunction in GaN/AlGaN with different Al compositions. Based on the mid- and far-infrared responsivity simulation of single-period GaN/AlGaN heterojunction detector, we investigate the mid- and far-infrared photon frequency upconversion efficiencies of multi-period GaN/AlGaN heterojunction detectors integrated with GaN/AlGaN violet light emitting diodes in relation to the GaN emitter layer thickness, intrinsic AlGaN barrier layer thickness, violet photon extraction efficiency, internal quantum efficiency, spatial frequency, and GaN emitter doping concentration. The results show that GaN-based infrared upconversion devices have high upconversion efficiency and good optoelectronic application prospect.

Erasing Distinguishability Using Quantum Frequency Up-Conversion

The frequency distinguishability of two single photons was successfully erased using single photon frequency up-conversion. A frequency nondegenerate photon pair generated via spontaneous four-wave mixing in a dispersion shifted fiber was used to emulate two telecom-band single photons that were in the same temporal mode but in different frequency modes. The frequencies of these photons were converted to the same frequency by using the sum-frequency generation process in periodically poled lithium niobate waveguides, while maintaining their temporal indistinguishability. As a result, the two converted photons exhibited a nonclassical dip in a Hong-Ou-Mandel quantum interference experiment. The present scheme will add flexibility to networking quantum information systems that use photons with various wavelengths.

Analysis of photonic frequency upconversion for radio-on-fiber applications using two-pump four-wave mixing in semiconductor optical amplifiers

A novel scheme of photonic frequency conversion based on two-pump four-wave mixing in a semiconductor optical amplifier is proposed. Characterized by its wide conversion range, the proposed scheme has the potential to generate millimeter waves at much higher frequency and convert several signal channels simultaneously. The system performance is analyzed through a numerical model, and the effect of the pump-signal pulse parameters on the conversion efficiency is discussed.

Photonic Monocycle Pulse Frequency Up-Conversion for Ultrawideband-Over-Fiber Applications

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We demonstrate a photonic monocycle pulse frequency up-conversion scheme for ultrawideband (UWB)- over-fiber applications using nonlinear polarization rotation arising in a semiconductor optical amplifier. For the first time, we have successfully realized the photonic up-conversion of UWB monocycle pulses with an optical local oscillator signal at 24 GHz in the whole <emphasis><formula><tex>$C$</tex> </formula></emphasis>-band. The up-converted UWB monocycle pulse at 24 GHz exhibits a power spectrum density fitting the UWB emission mask. After electrical down-conversion, the UWB monocycle pulse has shown low distortion induced by the optical mixing process. </para>

Enhanced light absorption in GaN∕AlGaN midinfrared detectors and application for pixel-less upconversion imaging

Based on the experimental responsivity of single-period GaN∕AlGaN midinfrared (MIR) heterojunction interfacial work-function internal photoemission (HEIWIP) detectors, we have optimized in detail the single- and multiperiod GaN∕AlGaN MIR HEIWIPs to enhance the light absorption in the detectors. The yielded parameters of emitter, intrinsic, and bottom contact layers could achieve large improvement of the MIR peak absorption efficiency in the multiperiod GaN∕AlGaN MIR HEIWIPs. Employing the concept of photon frequency upconversion, we have further investigated the realization of MIR pixel-less upconversion imaging through the integration of GaN∕AlGaN MIR HEIWIP with a GaN∕AlGaN violet light-emitting diode (LED). Under the optimized device structures, good imaging characteristics and high upconversion efficiency could be expected in the GaN∕AlGaN HEIWIP-LED MIR upconverter.

Imaging Characteristics and Quantum Efficiency: Key Properties for Pixelless Far-Infrared Semiconductor Upconversion Imaging Devices

Employing the concept of photon frequency upconversion, we have proposed two types of semiconductor upconverters to realize pixelless far-infrared (FIR) imaging. The upconverter consists of a GaAs FIR homojunction interfacial work-function internal photoemission detector integrated with a GaAs/AlGaAs near-infrared light-emitting diode (LED), or GaN/AlGaN mid-IR/FIR dual-band heterojunction detector with a GaN/AlGaN violet LED. We have studied in detail the dependences of the modulation transfer function and quantum efficiency of the upconverters on various device parameters. Through the application of resonant cavity to the GaAs-based upconverter, we can expect sharp and high-resolution image and improved quantum efficiency. In addition, due to the large light absorption in the GaN/AlGaN heterojunction detector, the quantum efficiency of the GaN-based upconverter is much higher than that of GaAs-based one.