Photonic Mixers Research Articles

Photonic THz mixers based on iron-doped InGaAs embedded in a plasmonic microcavity

We present an optoelectronic mixer for the terahertz (THz) frequency-domain based on an iron-doped InGaAs layer integrated in a plasmonic microcavity. We show that this structure, under 1550-nm-wavelength illumination, allows for more than 70% absorption efficiency in a 220 nm-thin InGaAs absorber and very high Roff/Ron >1000. It leads to THz mixers driven by 1550-nm lasers showing conversion loss as low as ∼30 dB at 300 GHz. Therefore, this design is very promising for application as receivers in high-data-rate wireless telecom, in cw-THz spectrometers, or in photonics-enabled THz spectrum analyzers.

Photonics-Assisted Simultaneous RF Channelization and Self-Interference Cancellation

Both RF channelization and self-interference cancellation are urgently required for modern in-band full-duplex systems. A photonics-assisted RF receiver for simultaneous wideband channelization and self-interference cancellation is proposed and demonstrated. The key is the implementation of dual optical frequency combs (OFCs) followed by microwave photonic image-reject mixers (IRMs) using a dual-output Hartley structure. The received RF signal and the reference signal are modulated to a pair of signal OFCs with orthogonal polarization states, respectively. The microwave photonic IRM is applied on each polarization state, respectively. For each local OFC comb line, two components will be sliced and downconverted from each copy of the optically-carried received RF signal. Meanwhile, another two components will be sliced and downconverted from the optically-carried reference signal. After combining the outputs of the IRMs, the components from the image signal and the self-interference signal will be eliminated simultaneously. Two channels of the signal of interest will be obtained for each local OFC comb line. Experimental results show that an RF signal with an instantaneous bandwidth of 6 GHz (from 7 to 13 GHz) is channelized into 6 channels, each of which has a 1-GHz bandwidth. The isolation of larger than 28 dB between the channels is realized, and the simultaneous self-interference cancellation and image-rejection are achieved.

A Photonic Microwave Frequency Quadrupler With Decoupled Bandwidth and Carrier Frequency for Multi-Octave LFM Signal Generation

A photonic microwave frequency quadrupler with decoupled bandwidth and carrier frequency for multi-octave linear frequency modulated (LFM) signal generation is proposed and experimentally demonstrated. The frequency quadrupler contains two phase-correlated photonic mixers incorporated in a single hardware, which has four input ports and an output port. An intermediate frequency (IF) LFM signal, is frequency doubled and up-converted to a radio frequency (RF) LFM signal which has a flipped frequency slope and doubled bandwidth in one photonic mixer. Then the generated RF LFM is heterodyned with the IF LFM in the other photonic mixer. At the output port, a frequency-quadrupled LFM signal, of which the carrier frequency is independent of the IF LFM and tunable, is obtained. Since the bandwidth and the center frequency of the generated signal are decoupled, a multi-octave signal is generated from a sub-octave signal with the proposed photonic-assisted frequency quadrupler.

Simultaneous frequency up/down converting interface based on a single hardware incorporating two phase-correlated photonic mixers.

A novel photonic frequency up/down-converting interface (FCI) with the capability of up-converting an intermediate frequency (IF) signal to a radio frequency (RF) signal and simultaneously down-converting a RF signal to a low IF signal is proposed, and a new application scenario, where both up and down frequency conversion stages of a deramp-on-receive linearly frequency modulated (LFM) continuous wave (CW) radar system are replaced by the FCI, is demonstrated. The five-port photonic FCI can be seen as two ultra-wideband phase-correlated photonic RF mixers incorporated in a single hardware, and the working frequency range of the FCI is up to Ka-band. The FCI is tested by an LFM waveform with 1GHz bandwidth in a deramp-on-receive LFM CW imaging radar system. In the test, the LFM signal can be transmitted and received correctly, and deramp output signals are able to coherently combine among multiple pulses, which generates a clear image of two point-targets with a 3dB range resolution of 15cm.

High-conversion-gain and deep-image-rejection Brillouin chip-based photonic RF mixer.

In this Letter, we report a chip-based photonic radio-frequency (RF) mixer with a maximum conversion gain of -9dB and image rejection ratio of 50 dB for 3.2 GHz to 13.2 GHz RF frequency range. This is achieved by the combined use of optical carrier suppression modulation and on-chip stimulated Brillouin scattering. These results will stimulate future implementations of integrated photonic RF mixers in complicated electromagnetic environments.

Multi-Band RF Transceiver Based on the Polarization Multiplexed Photonic LOs and Mixers

A photonics-based multi-band RF transceiver is proposed and demonstrated. Both for the multi-band transmitter and receiver sections, the polarization multiplexed photonic LO unit is shared, and the dual-polarization photonic mixer modules with similar structures are introduced. The architectural complexity is reduced, bringing benefits to the reliability, dimensions, and cost of the system. Based on the same transceiver, RF signals in four bands can be simultaneously generated, and the RF echoes can be processed to the same IF band with the interference effectively suppressed. The strict requirements with either the photonic or the electrical filters are avoided. Furthermore, the generation and processing capability can be extended to being with 4 N RF signals by introducing a polarization orthogonal optical frequency comb (OFC). The proposed architecture is therefore promising for the future cognitive radar systems which need to work in multiple bands and have a variety of functions to learn, infer, and react to the environment. A proof-of-concept experiment is taken. Four RF signals covering X, Ku, K and Ka bands with 1-GHz instantaneous bandwidth are simultaneously generated and processed. More than 26-dB crosstalk suppression ratio is realized for the four bands. The ranging operated in K- and Ka-bands simultaneously are also implemented.

Microwave photonic frequency down-conversion and channel switching for satellite communication.

We present a photonic approach to realize radio frequency (RF) down-conversion and intermediate frequency (IF) channel switching for satellite communication. Conventionally, photonic RF mixers always suffer from limitations of one operational state and one IF channel. We proposed a photonic repeater that can realize multiple frequency down-conversion states and different IF channel switching. Two separated RF ports and two independent local oscillator ports ensure the repeater can down-convert RF signals in different bands simultaneously. Based on the characteristic that orthogonally polarized optical signals cannot beat with each other, the crosstalk between different channels is alleviated. Since no optical filters are involved, the repeater can process broadband RF signals down-conversion and broadband IF signals channel switching. The proposed photonic repeater features compact structure, broad and different bands of operation, and no physical optical splitting, which is promising for a satellite payload.

Microwave Photonic Mixer Using DP-DDMZM for Next Generation 5G Cellular Systems

ABSTRACT Microwave frequency down-conversion at 4.5 GHz using proposed photonic mixer is analyzed on various aspects in this manuscript. The proposed microwave photonic down-converter employs a Dual-Parallel Dual-Drive Mach–Zehnder Modulator (DP–DDMZM) that makes the system more compact than previously reported photonic mixers. Suppressed carrier modulation technique is used to increase the sideband power, which improves conversion efficiency by 20 dB as compared to dual-series modulator based mixer. To examine the performance of the proposed system for 5 G digital data transmission and reception, dispersion analysis over the length of fiber is performed. Furthermore, its performance for various digital modulation schemes is discussed.

Photonic Mixer Incorporating All-Optical Microwave Frequency Generator Based on Stimulated Brillouin Scattering Using Single Laser Source

In this paper, we report the theoretical and experimental implementation of a photonic mixer for Radio-Over-Fiber (RoF) transmission systems, which incorporates an all-optical 10.87 GHz microwave frequency signal generator based on beating laser frequency with its first order Stimulated Brillouin Scattering (SBS) frequency shift. A 13GHz Radio Frequency (RF) is down-converted to 2.13 GHz Intermediate Frequency (IF) signal. The proposed system configuration represents a cost-effective photonic mixer that can be deployed for up and down conversion around 11 GHz in RoF transmission systems. The optically generated microwave signal of 10.87 GHz has a phase noise of -109 dBc/Hz at 15-MHz offset. The proposed photonic mixer exhibits a Spurious-Free Dynamic Range (SFDR) of 93dB.Hz 2/3 . This RoF transmission system configuration deploys dual parallel Gallium Arsenide (GaAs) Mach Zehnder Modulator as a photonic mixer, and a single laser source as a Brillouin pump and as an optical carrier at the same time. To the best of our knowledge, this type of photonic mixers has not been reported in the literature.

Theoretical investigation of the capture effect in IMDD-based microwave photonic mixers

We study the large-signal behavior of microwave photonic (MWP) mixers to investigate the small-signal suppression phenomenon commonly referred to as the capture effect. We introduce and theoretically study the capture effect in the context of MWP mixers. Theoretical expressions are derived for calculating the capture effect in three basic MWP mixer types based on intensity-modulation direct-detection (IMDD). We show that the capture effect not only is a function of the power ratio between the input radio-frequency (RF) signals to the MWP mixers, but also depends on the absolute value of their powers. In addition, it is shown that the capture effect of an IMDD-based MWP mixer depends on the fiber dispersion and chirping of the optical modulator, but does not depend on the noise of its components and bias drift of the optical modulator. We extend the study to different unequal-power frequency components of a signal, and as a practical example, we investigate the capture effect when a narrowband FM signal is applied to the RF input of an IMDD-based MWP mixer, theoretically demonstrating considerations and limitations in using MWP mixers.

Ultra-Wideband and Adaptive Photonic Signal Processing of Microwave Signals

Microwave photonic techniques are attractive for processing high bandwidth signals, overcoming inherent electronic limitations. These processors provide new capabilities for realizing adaptive processing over extremely wide microwave frequency ranges, ultra-wideband operation, and electromagnetic interference immunity. In-fiber signal processors are inherently compatible with fiber-wireless systems, and can provide connectivity with in-built signal conditioning. Recent new methods in wideband microwave photonic processing are presented, including ultra-wideband phase shifters and true time delays for phased array beamforming, widely tunable single passband filters, switchable microwave photonic filters, wideband photonic mixers, high-resolution multiple frequency microwave photonic measurement systems, and photonic RF memory structures.

Microwave photonic signal processing

Photonic signal processing offers the advantages of large time-bandwidth capabilities to overcome inherent electronic limitations. In-fibre signal processors are inherently compatible with fibre optic microwave systems that can integrate with wireless antennas, and can provide connectivity with in-built signal conditioning and electromagnetic interference immunity. Recent methods in wideband and adaptive signal processing, which address the challenge of realising programmable microwave photonic phase shifters and true-time delay elements for phased array beamforming; ultra-wideband Hilbert transformers; single passband, widely tunable, and switchable microwave photonic filters; and ultra-wideband microwave photonic mixers, are described. In addition, a new microwave photonic mixer structure is presented, which is based on using the inherent frequency selectivity of the stimulated Brillouin scattering loss spectrum to suppress the carrier of a dual-phase modulated optical signal. Results for the new microwave photonic mixer demonstrate an extremely wide bandwidth operation of 0.2 to 20 GHz and a large conversion efficiency improvement compared to the conventional microwave photonic mixer.

Simultaneous broadband microwave downconversion and programmable complex filtering by optical frequency comb shaping

High-repetition-rate optical frequency combs can act as broadband photonic mixers and downconvert a microwave signal to an intermediate frequency (IF) band so that it becomes accessible with high-speed electronics. In this Letter, we show that with line-by-line pulse shaping and dispersive propagation, the photonic mixer can simultaneously perform programmable multitap complex-coefficient-filtering within the IF band. This solution opens new possibilities for microwave signal processing by combining the flexibility of optoelectronic frequency comb technology with high-speed analog-to-digital converters.

Losses from long-living photoelectrons in terahertz-generating continuous-wave photomixers

The extraction of continuous-wave terahertz (THz) power from photonic mixers is known to be hampered by input power limitations, low conversion efficiencies, and saturation effects. Using vertically illuminated low-temperature-grown GaAs travelling-wave mixers with a coplanar stripline geometry, a mechanism of illumination-dependent reabsorption of the THz-power generated by the mixer was isolated. We find evidence that it is related to a substantial density of long-living photoelectrons (several nanoseconds). The proposed mechanism is expected to impact the performance of photonic terahertz mixers at high input powers, also of those based on transit-time-dominated semiconductor structures.

Semi-Analytical Calculation of Terahertz Signal Generated from Photocurrent Radiation in Traveling-Wave Photonic Mixers

A semi-analytical method based on distributed source transmission line model is proposed to analyze a traveling-wave terahertz photomixer integrated with a coplanar stripline waveguide. Multilayer spectral domain method along with complex image technique have been applied to calculate the distributed voltage source element in the transmission line representation. To find the coupled terahertz signal along the coplanar stripline, the transmission line equations are solved. The results obtained from the proposed method are verified by the full wave analysis.

Terahertz photonic mixers as local oscillators for hot electron bolometer and superconductor-insulator-superconductor astronomical receivers

A pump experiment of two astronomical heterodyne receivers, a superconductor- insulator-superconductor (SIS) receiver at 450GHz and a hot-electron-bolometer (HEB) receiver at 750GHz, is reported. A low-temperature-grown GaAs metal-semiconductor-metal photonic local oscillator (LO) was illuminated by two near infrared semiconductor lasers, generating a beat frequency in the submillimeter range. I-V junction characteristics for different LO pump power levels demonstrate that the power delivered by the photomixer is sufficient to pump a SIS and a HEB mixer. SIS receiver noise temperatures were compared using a conventional solid-state LO and a photonic LO. In both cases, the best receiver noise temperature was identical (Tsys=170K).

Travelling-wave photonic mixers for increased continuous-wave power beyond 1 THz

Travelling-wave designs for terahertz photonic mixers have been shown to surpass limitations of small-area designs and therefore have the potential to generate greatly increased continuous-wave (CW) powers at frequencies well above 1 THz and towards 2 THz. Still a lot of optimization process has to be done and new materials tested. Results with different geometries and materials made to date are compared.

Large-area traveling-wave photonic mixers for increased continuous terahertz power

A large-aperture design for terahertz traveling-wave photomixers, continuously pumped free space by two detuned diode lasers, is proposed and experimentally verified for devices based on low-temperature-grown GaAs (LT-GaAs). It combines the advantages of conventional interdigitated small-area structures and traveling-wave devices. An output power of 1 μW at the mixing frequency of 1 THz was measured in initial testing, which meets local oscillator power requirements for superconducting heterodyne mixer devices.

Analysis of hybrid modulation techniques in MZ‐EOM‐based photonic mixers to overcome dispersion‐induced power penalty in up‐converting millimeter‐wave fiber‐optic links

In this letter, we investigate the combination of single-sideband (SSB) and double-sideband (DSB) modulation techniques in up-converting millimeter-wave fiber-optic links. It is shown that the dispersion-induced power penalty due to fiber chromatic dispersion may be mitigated and eventually overcome by employing MZ-EOM SSB modulation over the local oscillator signal and/or the intermediate frequency signal. Experimental results are provided for the hybrid modulation scheme which combines both SSB and DSB. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 127–129, 1999.

Analysis of hybrid modulation techniques in MZ-EOM-based photonic mixers to overcome dispersion-induced power penalty in up-converting millimeter-wave fiber-optic links

In this letter, we investigate the combination of single-sideband (SSB) and double-sideband (DSB) modulation techniques in up-converting millimeter-wave fiber-optic links. It is shown that the dispersion-induced power penalty due to fiber chromatic dispersion may be mitigated and eventually overcome by employing MZ-EOM SSB modulation over the local oscillator signal and/or the intermediate frequency signal. Experimental results are provided for the hybrid modulation scheme which combines both SSB and DSB. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 127–129, 1999.