Frequency Quadrupler Research Articles

Enhanced UV Nonlinear Optical Properties in Layered Germanous Phosphites through Functional Group Sequential Construction

AbstractThis study pioneers a novel strategy for synthesizing solar‐blind ultraviolet (UV) nonlinear optical (NLO) crystals through functional groups sequential construction, effectively addressing the inherent trade‐offs among broad transmittance, enhanced second‐harmonic generation (SHG), and optimal birefringence. We have developed two innovative van der Waals layered germanous phosphites: GeHPO3, the first Ge(II)‐based oxide NLO crystal which exhibits a black phosphorus‐like structure, and K(GeHPO3)2Br, distinguished by its exceptional birefringence and graphene‐like structure. Significantly, GeHPO3 exhibits a remarkable array of NLO properties, including the highest SHG coefficient recorded among all NLO crystals for phase‐matching and generating 266 nm coherent light via quadruple frequency conversion. It delivers a potent SHG intensity, surpassing KH2PO4 (KDP) by 10.3 times at 1064 nm and β‐BaB2O4 by 1.3 times at 532 nm, complemented by a distinct UV absorption edge at 211 nm and moderate birefringence of 0.062 at 546 nm. Comprehensive theoretical analysis links these exceptional characteristics to the unique NLO‐active GeO34− units and the distinctive, highly ordered layered structures. Our findings deliver essential experimental insights into the development of Ge(II)‐based optoelectronic materials and present a strategic blueprint for engineering structure‐driven functional materials with customized properties.

Enhanced UV Nonlinear Optical Properties in Layered Germanous Phosphites through Functional Group Sequential Construction.

This study pioneers a novel strategy for synthesizing solar-blind ultraviolet (UV) nonlinear optical (NLO) crystals through functional groups sequential construction, effectively addressing the inherent trade-offs among broad transmittance, enhanced second-harmonic generation (SHG), and optimal birefringence. We have developed two innovative van der Waals layered germanous phosphites: GeHPO3, the first Ge(II)-based oxide NLO crystal which exhibits a black phosphorus-like structure, and K(GeHPO3)2Br, distinguished by its exceptional birefringence and graphene-like structure. Significantly, GeHPO3 exhibits a remarkable array of NLO properties, including the highest SHG coefficient recorded among all NLO crystals for phase-matching and generating 266 nm coherent light via quadruple frequency conversion. It delivers a potent SHG intensity, surpassing KH2PO4 (KDP) by 10.3 times at 1064 nm and β-BaB2O4 by 1.3 times at 532 nm, complemented by a distinct UV absorption edge at 211 nm and moderate birefringence of 0.062 at 546 nm. Comprehensive theoretical analysis links these exceptional characteristics to the unique NLO-active GeO3 4- units and the distinctive, highly ordered layered structures. Our findings deliver essential experimental insights into the development of Ge(II)-based optoelectronic materials and present a strategic blueprint for engineering structure-driven functional materials with customized properties.

High‐resolution 3D imaging by microwave photonic time division multiplexing‐multiple‐input‐multiple‐output radar with broadband digital beamforming

AbstractA broadband microwave photonic time division multiplexing (TDM) multiple‐input‐multiple‐output (MIMO) radar is proposed in which photonic frequency quadrupling is adopted to generate broadband radar signals and photonic frequency mixing is implemented for de‐chirping processing of radar echoes. By utilising two radio frequency switches to control the signal transmission and reception, TDM‐MIMO mechanism is formed using a single microwave photonic radar transceiver. This microwave photonic TDM‐MIMO radar not only achieves high range resolution using broadband processing but also enables high angular resolution and forward‐looking imaging capability with low system complexity. Besides, a broadband digital beamforming (DBF) method is introduced to solve the broadband beam squint and broadening problems and implement near‐field correction. In the experiment, a microwave photonic TDM‐MIMO radar with an 8×8 T‐shape antenna array is established with a bandwidth of 8 GHz (18–26 GHz) in each channel. The range and angular resolutions are estimated to be ∼2 cm and ∼2°, respectively. Applying the broadband DBF method, high‐resolution 3D imaging of small targets is achieved with good focusing of targets and deep suppression of grating lobes and side lobes. Hence, the proposed microwave photonic TDM‐MIMO radar with broadband DBF provides a promising solution for high‐resolution 3D imaging.

Optical Upconversion of OFDM Signals for Next Generation Fronthauling Using Frequency Doubling and Quadrupling

Optical Upconversion of OFDM Signals for Next Generation Fronthauling Using Frequency Doubling and Quadrupling

A 50-GHz SiGe Frequency Quadrupler With 42-dBc Harmonic Rejection and 17% Peak Total Efficiency

A 50-GHz SiGe Frequency Quadrupler With 42-dBc Harmonic Rejection and 17% Peak Total Efficiency

Research on the vibration mechanism of compressor complex exhaust pipeline based on transient flow

The periodic exhaust of the compressor often induces gas flow fluctuations within the pipeline, leading to vibrations. Excessive vibration can lead to fatigue, cracks, loosening of components, and resulting in local leakage, which may easily lead to fire, explosion, and secondary hazards. Therefore, in this paper, a computational model for the transient flow field of the compressor exhaust pipeline was established, using the pulse excitation method and Fluent software, the natural frequencies of the gas column in the pipeline were calculated, and the patterns of oscillation decay of the gas column wave propagating back and forth within three exhaust pipes were researched. The mechanism behind the pipeline pressure pulsation and the influence of pipeline structural parameters on the natural frequencies of the gas column were explored. The calculation results show that the first-order natural frequency of the gas column is very close to the double frequency of the compressor excitation frequency at 3.33Hz, and the second-order natural frequency of the gas column is very close to the quadruple frequency of the compressor excitation frequency at 3.33Hz, which may cause significant pipeline vibrations. Altering the pipeline structure, especially when influenced by airflow branching after a tee junction, results in complex changes in the natural frequencies of the gas column. Furthermore, the structural natural frequencies of the pipeline were obtained through the finite element. It has been observed that resonance phenomena exist among the structural natural frequencies and their harmonics of the pipeline and the natural frequencies of the gas column and their harmonics, as well as multiples of the excitation frequency. These results lay the foundation for understanding the vibration mechanism of the pipeline and finding ways to reduce vibration.

The generation of a fourth-harmonic probe and its application in Nomarski interferometry at Shengguang-II.

In this work, a design for the generation of a 4ω (263-nm) probe converted from a 1ω (1053-nm) laser is presented. The design is based on a beta-barium borate and potassium dihydrogen phosphate two-step frequency-conversion process. A suitable configuration for Nomarski interferometry based on the 4ω probe is proposed, for measuring the electron density of laser-produced plasmas. The signal-to-noise ratio of the output 4ω probe to 1ω and 2ω light after frequency quadrupling and harmonic separation is 103 with a 0.5 GW/cm21ω input but decreases to ∼102 at intensities below 0.1 GW/cm2. Additional noise suppression by a factor of 104 is achieved using filters before the interferometer recording camera. The spatial resolution of the diagnostic can reach 5.2 µm for a 10% modulation transfer function. An experiment validating the probe diagnostic system is conducted at the Shengguang-II laser facility. A clear interferogram of an aluminum plasma is obtained with 0.1 GW/cm2 input, suggesting a maximal electron density of about 2.5 × 1020 cm-3 as retrieved through an inverse-Abel transform. The design proposed in this paper is appropriate for a small laser device or a large laser facility that lacks a separate diagnostic beam, and it is an inexpensive solution as it requires small-aperture 1ω input at a relatively low intensity. All the key parameters necessary to implement the design are provided in detail, making it straightforward to reproduce or transplant the system for specific uses.

Beam commissioning of the SARAF Injector and MEBT (protons)

The SARAF Phase II cryogenic linear accelerator (linac) is currently under construction and will be commissioned through collaborative efforts between SNRC and CEA. The linac will accelerate a 5 mA pulsed/continuous wave (CW) proton and deuteron beam, reaching energies of up to 35 MeV and 40 MeV, respectively. The linac injector consists of Phase I components, including an ECR ion source, a Low-Energy Beam Transport (LEBT) line, and a 4-rod Radio Frequency Quadruple (RFQ). Additionally, a new Medium Energy Beam Transport (MEBT) line has been installed and integrated into the injector infrastructure. The MEBT includes three rebuncher resonators, magneto-optical elements, and beam diagnostics. The MEBT beam diagnostics, as well as the Phase I D-plate installed downstream, were used for beam characterization. The downstream-installed Temporary Beam Line (TBL) and a prototype of the Gallium Indium Liquid Target (GALIT) were used for commissioning, operating at high beam duty cycles, including CW mode. The report describes the proton beam commissioning process of the injector prior to the delivery of the cryomodules, scheduled for the second half of 2023.

A 52–65 GHz Frequency Quadrupler With Low Conversion Loss and High Harmonic Rejection Ratio in 28-nm CMOS

This brief presents a 52-65 GHz frequency quadrupler with low conversion loss and high harmonic rejection ratio based on 28-nm bulk CMOS process. The frequency quadrupler includes two stages balanced frequency push-push doublers (PPD) cascaded with common-gate buffers. A series LC pair is placed between the PPD and the buffer of the first stage, which not only improves the conversion gain, but also suppresses the unwanted fundamental signals. A filter-integrated matching network is designed as the output matching network to reject undesired harmonics. As a result, the proposed design exhibits advantages in conversion gain and harmonic rejection ratio. The measured peak output power is -1.8 dBm and the output power 3-dB bandwidth is 52-65 GHz when the input power is 0 dBm. The even and odd harmonics rejection ratios are better than 35 dBc and 45 dBc, respectively, which can be used in high-performance mm-Wave LO chain.

A 208-MHz, 0.75-mW Self-Calibrated Reference Frequency Quadrupler for a 2-GHz Fractional-N Ring-PLL in 4-nm FinFET CMOS

This paper presents a 208-MHz, 0.75-mW selfcalibrated reference frequency quadrupler (RFQ), which provides a 4x higher reference clock with minimal deterministic frequency error. The digital-assisted calibration technique is exploited to compensate wide range of frequency and duty cycle errors and to reduce the noise degradation of analog calibration loop. Also, instead of utilizing a duty cycle corrector for 2x clock, reusing a delay cell reduces the power consumption by 50%. The fractional-N ring-PLL with the proposed RFQ was implemented in a 4nm FinFET CMOS process. The active area of the RFQ is 0.0175mm2 while the whole PLL occupies the area of 0.109mm2. By using the RFQ, the measured RMS-jitter of the PLL is definitely improved from 6.6ps to 3.35ps at 1.92GHz output frequency.

Photonics-Based Broadband Radar With Coherent Receiving for High-Resolution Detection

A microwave photonics radar with interference-suppressed high-resolution detection ability is proposed and experimentally demonstrated based on optical frequency quadrupling and coherent receiving de-chirping. Which is achieved by using a dual-parallel Mach-Zehnder modulator to perform base-band signal frequency quadrupling in transmitter, and an optical coherent receiver to realize balanced photonic in-phase/ quadrature (I/Q) de-chirping of the broadband radar echoes in receiver. Thanks to the frequency multiplication, a wideband radar transmitting signal can be generated with low speed electron devices. Meanwhile, interference-free detection by suppressing undesired common-mode interferences and image frequency could be achieved with balanced photonic I/Q de-chirping broadband radar echoes. In the experiment, a photonics-based K-band radar with a bandwidth of 8 GHz is demonstrated, corresponding to a resolution better than 2.0 cm. In addition, the balanced photonic I/Q de-chirping receiver achieves an image-rejection ratio of 40.4 dB. The proposed radar detection system is a promising candidate in interference-suppressed high-resolution radar application.

High-power deep-ultraviolet light generation at 266 nm from frequency quadrupling of a picosecond pulsed 1064 nm laser with a Nd:YVO4 amplifier pumped by a 914 nm laser diode.

We report the generation of picosecond pulsed light at a 266 nm wavelength with an average power of 53 W. We developed a picosecond pulsed 1064 nm laser source with an average power of 261 W, a repetition rate of 1 MHz, and a pulse duration of 14 ps, using a gain-switched DFB laser diode as a seed laser and a 914 nm laser-diode-pumped Nd-doped YVO4 power amplifier. We achieved stable generation of 266 nm light with an average power of 53 W from frequency quadrupling using an LBO and a CLBO crystals. The amplified power of 261 W and the 266 nm average power of 53 W from the 914 nm pumped Nd:YVO4 amplifier are the highest ever reported, to the best of our knowledge.

High-Accuracy and High-Tolerance Laser Encoder With a Grating-Pyramid Configuration

Laser encoders is promising positioning sensors for nanometer measurement. It is a key challenge for laser encoders to offer high accuracy while ensuring high tolerance in service. In this paper, we present a laser encoder employing a grating-pyramid configuration. This configuration realizes double diffraction via a single retro-reflector, which offers the following two advantages: (i) providing high-resolution output signals due to optical quadruple frequency; (ii) improving alignment tolerance due to retro-reflection of the single pyramid. Its operating principle is described in detail, and the performance are evaluated. Simulation result presents that stand-off error and pitch error are the critical head-to-scale tolerance for the developed laser encoder. Experiment result shows that the laser encoder offers a stand-off tolerance of ±0.68 mm and a pitch tolerance of ±1.67°. Furthermore, an interpolation accuracy of 3 nm is achieved, which indicates that the laser encoder would achieve nanometer-level resolution. Both simulation and experimental results demonstrate its high-accuracy and high-tolerance.

A High-Efficiency W-Band Frequency Quadrupler With Current-Reusing Stacked Push–Push Stages

This letter presents a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula> -band frequency quadrupler with current-reusing stacked push–push doubler (PPD) stages, implemented in a 180-nm SiGe BiCMOS process. A series balun is used between two PPDs to generate differential signals for the second PPD stage, while also allowing half of the second stage’s current to be reused in the first doubler stage, thereby improving efficiency. The circuit exhibits a compelling output power, peak conversion gain, bandwidth, harmonic rejection, and efficiency for a quadrupler in this frequency range across a 3-dB bandwidth of 76–94 GHz. The quadrupler achieves a peak conversion gain of 13.5 dB, a peak output power of 8.7 dBm, and a maximum dc-to-RF efficiency of 6.4%.

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.

A Frequency Quadrupler in 130-nm SiGe With Stack Multiport-Driven Matching Achieving 37.4% Instantaneous Bandwidth

In this letter, a wideband and high harmonic rejection frequency quadrupler, which consists of a two-stage push–push pair frequency doubler, is demonstrated in a 130-nm SiGe technology. A novel stack multiport-driven matching (SMDM) technology is employed in inter-stage matching to address the limited bandwidth, providing a more efficient method to match the dual-tank networks to 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> . The SMDM also provides dc pass-through with the common-base (CB) amplifier, thereby increasing the conversion gain (CG). Additionally, the undesired harmonics are suppressed by the dual-tank networks loaded on the collector of the two-stage doubler. The measured results show that the 3-dB bandwidth of the output power is about 6.8 GHz from 14.8 to 21.6 GHz, that is, 37.4%. The worst-case harmonic rejection ratios (HRRs) are 22.1 dBc at the second-order harmonic, 44.4 dBc at the fundamental harmonic, and 35.7 dBc at the third-order harmonic with input power 2 dBm over the entire operating bandwidth, respectively. The frequency quadrupler occupies an area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.83\times0.5$ </tex-math></inline-formula> mm2.

A 60-GHz Hybrid FMCW-Doppler Radar for Vibration Detection With a Robust I/Q Calibration Method

In the field of noncontact sensing, both the continuous-wave (CW) Doppler radar and the frequency-modulated CW (FMCW) radar have their own superiorities. A combination of these two radar modes would be a suitable choice to accommodate various application scenarios. This article presents a 60-GHz hybrid FMCW-Doppler radar transceiver fabricated in a 65-nm CMOS process. An on-chip frequency quadrupler driven by a 15-GHz external signal source is utilized for the 60-GHz hybrid waveform generation. Based on the hybrid operating modes, a robust I/Q imbalance calibration method is also proposed. Specifically, in the Doppler radar mode, the imbalance factors are extracted by evaluating the quadrature beat signals during the FMCW period, and then the interferometry signals are calibrated to improve the detection performance. Unlike the trajectory-based ellipse-fitting method, the accuracy of the estimated imbalance factor is independent of the target displacement. Compared with the test-signal-based imbalance factors extraction ahead of the target detection, the real-time extraction during the target detection is more efficient and can also mitigate the estimation errors caused by environmental variations. With the proposed hybrid radar system and the I/Q calibration method, an 80-mm linear displacement is recovered with a 0.016-mm root mean square error (RMSE), and a periodic vibration with a 1- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> amplitude is detected with a 16.4-dB signal-to-noise ratio (SNR). Multiple-target detection is also performed in the FMCW radar mode, and the vibration trajectories are recovered accurately.

Amplification and frequency quadrupling of picosecond long duration burst-mode laser

By employing two laser diodes (LDs) dual-end pulse-pumped a Nd:YVO4 crystal amplification, LiB3O5 (LBO) crystal frequency doubling and β-BaB2O4 (BBO) crystal frequency quadrupling, a 266 nm picosecond burst-mode laser is observed. The macro-pulse width of 16 μs and the macro-pulse repetition rate of 550 Hz are realized by using the electro-optic modulator (EOM) to pick up micro-pulses output from a 1064 nm laser source with pulse width of 18 ps and frequency repetition of 178 MHz. By actually delaying the time between front edges of macro-pulses and pump pulses, flat-top amplified macro-pulse envelope is obtained. The amplified macro-pulse has the micro-pulse energy of 787 nJ at the optimal delay time of 49.5 μs, corresponding beam quality ofMx2 = 1.30, My2=1.29. The frequency doubling burst-mode laser is obtained with the micro-pulse energy of 531 nJ, corresponding to beam quality ofMx2 = 1.15, My2=1.18. The conversion efficiency from 1064 nm to 532 nm is 67%. Elliptically focused 532 nm beam is used to match the narrow longitudinal acceptance angle of type-Ⅰ BBO crystal. The 266 nm micro-pulses have the pulse energy of 135 nJ. The conversion efficiency from 532 nm to 266 nm is 25%, and the total conversion efficiency from 1064 nm to 266 nm is 17%. The beam quality of the 266 nm burst-mode laser is Mx2 = 1.15 and My2 = 1.25.

Digital Keying Enabled by Reconfigurable 2D Modulators.

Energy, area, and bandwidth efficient communication primitives are essential to sustain the rapid increase in connectivity among internet-of-things (IoT) edge devices. While IoT edge-sensing, edge-computing, and edge-storage have witnessed innovation in materials and devices, IoT edge communication is yet to experience such transformation. The aging silicon (Si)-based complementary metal-oxide-semiconductor (CMOS) technology continues to remain the mainstay of communication devices where they are used to implement amplitude, frequency, and phase shift keying (amplitude-shift keying [ASK]/frequency-shift keying [FSK]/phase-shift keying [PSK]). Keying allows digital information to be communicated over a radio channel. While CMOS-based keying devices have evolved over the years, their hardware footprint and energy consumption are major concerns for resource constrained IoT communication. Furthermore, separate circuit designs and hardware elements are needed for each keying scheme and achieving multibit modulation to improve bandwidth efficiency remains a challenge. Here, a reconfigurable modulator is introduced that exploits unique ambipolar transport and programmable Dirac voltage in ultrathin MoTe2 field-effect transistors to achieve ASK, FSK, and PSK modulation. Furthermore, by integrating two programmed MoTe2 field-effect transistors, multibit data modulation is demonstrated, which improves the bandwidth efficiency by 200%. Finally, a frequency quadrupler is also realized exploiting the unique "double-well" transfer characteristic.

An E-band CMOS frequency quadrupler with 1.7-dBm output power and 45-dB fundamental suppression

This paper presents an E-band frequency quadrupler in 40-nm CMOS technology. The circuit employs two push–push frequency doublers and two single-stage neutralized amplifiers. The pseudo-differential class-B biased cascode topology is adopted for the frequency doubler, which improves the reverse isolation and the conversion gain. Neutralization technique is applied to increase the stability and the power gain of the amplifiers simultaneously. The stacked transformers are used for single-ended-to-differential transformation as well as output bandpass filtering. The output bandpass filter enhances the 4th-harmonic output power, while rejecting the undesired harmonics, especially the 2nd harmonic. The core chip is 0.23 mm2 in size and consumes 34 mW. The measured 4th harmonic achieves a maximum output power of 1.7 dBm with a peak conversion gain of 3.4 dB at 76 GHz. The fundamental and 2nd-harmonic suppressions of over 45 and 20 dB are achieved for the spectrum from 74 to 82 GHz, respectively.