Cascaded Four-wave Mixing Research Articles

Dynamic control of cascaded four-wave mixing via re-configurable dispersion.

We integrate a spatial light modulator-based dispersion controller into a cascaded four-wave mixing (CFWM) system. By tuning the group delay dispersion (GDD) and fourth-order dispersion (FOD) terms, we control the CFWM phase matching and demonstrate an output bandwidth tuning of over 3.3×. At the maximum bandwidth, our system covers the telecommunications S-, C-, and L-bands (1466-1641 nm) with an average output power of 300 mW, which is contained in 52 individual lines spaced 374 GHz apart. This method represents a reconfigurable alternative to photonic crystal fibers for dispersion engineering and allows for the use of step-index fiber and customizable power spectral density (PSD) profiles.

Tunable Continuous‐Variable Tripartite Entanglement via Simultaneous and Ordinal Cascaded Nonlinear Processes

AbstractMultipartite quantum entanglement plays a vital role in both fundamental science and quantum applications. The cascaded four‐wave mixing (FWM) process is an effective method to prepare multipartite entanglement, however, the physical nature of entanglement based on different cascading paths, i.e., simultaneous cascaded FWM (SC‐FWM) and ordinal cascaded FWM (OC‐FWM), has not yet been conclusively determined. In this article, tunable continuous‐variable (CV) triple‐mode entanglement is proposed to be generated by using both the SC‐FWM and OC‐FWM schemes. The simulation results reveal that the absorption/dispersion properties of the two nonlinear processes can be efficiently tuned by varying the optical parameters (i.e., the photon detuning and the nonlinear susceptibility), resulting in triple‐mode CV entanglement with tunable properties. Compared with the OC‐FWM scheme, the SC‐FWM scheme has a broader entanglement bandwidth and a higher degree of entanglement, where the tripartite entanglement region is 4.38% larger than that of the OC‐FWM scheme. Furthermore, these results indicate that the SC‐FWM scheme has a more compact and stable mode structure with better entanglement performance. Such tunable optical triple‐mode entanglement may find applications in specific quantum communication protocols and pave the way for implementing and manipulating multichannel quantum networks.

Phase Conjugated Mode Conversion Enabled by Two-stage Cascaded Four-wave Mixing Processes

Phase Conjugated Mode Conversion Enabled by Two-stage Cascaded Four-wave Mixing Processes

Enhancement of quadripartite quantum correlation via phase-sensitive cascaded four-wave mixing process

Multipartite quantum correlation is important for both fundamental science and quantum information processing. Its enhancement is critical to improve the performance of physical systems. Therefore, it is of great practical significance to study the enhancement of multipartite quantum correlation. Here, we theoretically investigate a scheme for enhancing quadripartite quantum correlation by utilizing a phase-sensitive cascaded four-wave mixing (CFWM) process. We find that the intensity-difference squeezing (IDS) among the four output beams generated by the phase-insensitive CFWM process can be largely enhanced by introducing the phase-sensitive CFWM process. We also find that our phase-sensitive CFWM process can be used to generate intensity-sum squeezing (ISS), which cannot be generated by the phase-insensitive CFWM process. Moreover, we find that the maximum squeezing value of ISS is equal to that of IDS when the intensity gains of the three four-wave mixing processes are equal in the phase-sensitive cascaded scheme. In the end, we discuss the effects of the losses and the phase fluctuations on the squeezing values of our phase-sensitive CFWM process and the corresponding phase-insensitive CFWM process with the same intensity gains. It can be seen that the squeezing enhancement of our phase-sensitive CFWM process holds also in presence of the losses and the phase fluctuations. Our results pave the way for experimental implementation and may find applications in quantum metrology and quantum communication.

Pulse compression of a single-frequency Q-switched fiber laser based on the cascaded four-wave mixing effect

A pulse compressing technology of single-frequency Q-switched laser based on the cascaded four-wave mixing (CFWM) effect is demonstrated theoretically and experimentally, for the first time to the best of our knowledge. A theoretical model of the pulse compression is established through deconstructing the pulse duration evolution in the high-order Stokes and anti-Stokes lights of CFWM. A pulse compression ratio of (2|m|+1)1/2 is quantificationally obtained with m corresponding to the order number of the CFWM light. Utilizing dual-wavelength (DW) single-frequency Q-switched laser injected into a highly nonlinear fiber (HNLF), the pulse compression and the spectral broadening phenomenon are observed simultaneously. As the order number of the CFWM light increases from 0-order to 3-order, the pulse duration has reduced from 115 ns to 47 ns with a compression ratio of 2.45, which is essentially consistent with the theoretical analysis. The pulse compressing technique by CFWM is conducive to promoting the performance development of the single-frequency Q-switched laser, which can improve the system precision in the Lidar, trace gas detection, and high-precision ranging. Furthermore, this technology based on time-frequency transformation dynamics may be generally applicable to other single-frequency pulsed fiber lasers.

Generation of tripartite squeezed state by cascaded four-wave mixing in single hot rubidium atomic system

We report the quantum correlated triple beams via cascaded four-wave mixing (CFWM) amplified in single hot atomic vapor. Experimentally, we show that strong quantum correlation of three light beams, among them any two’s quantum correlation is characterized by the maximum value of intensity-difference squeezing (IDS) about −7.8 ± 0.3 dB. We found there is IDS between two idler beams, because two pairs of Einstein–Podolsky–Rosen injections potentially exist in our system. Besides, CFWM can emit three-mode beams at three different frequencies, in which these beams can be well separated in the spatial domain. Moreover, much difference with other methods, the injecting probe field can manipulate the gain and IDS of output three-mode light beams, which is resulting from competition relationship between cascaded two four-wave mixing processes. More interestingly, Autler–Townes splitting of gain peaks of output signals due to dressing effect of pumping fields, will lead to the evolution of measured two- and three-mode IDS from single-mode to multi-mode at frequency domain. This result will provide a multimode quantum resource which can potentially realize multimode entanglement and quantum networks.

Multi-Way Noiseless Signal Amplification in a Symmetrical Cascaded Four-Wave Mixing Process

According to the fundamental laws of quantum optics, vacuum noise is inevitably added to the signal when one tries to amplify a signal. However, it has been recently shown that noiseless signal amplification can be realized when a phase-sensitive process is involved. Two phase-sensitive schemes, a correlation injection scheme and a two-beam phase-sensitive amplifier scheme, are both proposed to realize multi-way noiseless signal amplification in a symmetrical cascaded four-wave mixing process. We theoretically study the possibility of the realization of four-way noiseless signal amplification by using these two schemes. The results show that the correlation injection scheme can only realize one-way noiseless signal amplification, but that the two-beam phase-sensitive amplifier scheme can lead to four-way noise figure values below 1. Our results here may find potential applications in quantum information processing, e.g., the realization of quantum information tap and quantum non-demolition measurement, etc.

Generation of octapartite entanglement by connecting two symmetric cascaded four-wave mixing processes with one linear beam splitter

We theoretically propose a scheme for generating full octapartite entanglement using two symmetric cascaded four-wave mixing (FWM) processes and one linear beam splitter (BS), in which two independent symmetric cascaded FWM processes are connected by a BS. To present the entanglement properties of the system, we first verify that the generated state is a H -graph state by exploiting the graphical calculus for Gaussian pure states, and reveal the internal interaction of the generated state by using the derived coupling strength matrix. We proceed with investigating the possibility of this scheme for generating octapartite entanglement by applying the positivity under a partial transposition criterion. The results show that there exists full octapartite entanglement in the whole gain region, and the degree of entanglement increases as the power gain increases. In addition, we investigate the effect of transmissivity of BS on the entanglement properties of the system and the dependence of bipartite entanglement on the power gain and the transmissivity of BS. Our results give a simple way to increase the scale of entanglement by linear optics and cascaded FWM processes.

Generation of four-mode cluster states based on cascade four-wave mixing process

As a crucial quantum resource for quantum computing and quantum information processing, cluster state has attracted extensive attention due to its unique entanglement properties and rich structures. In this work, we theoretically propose a scheme for generating four-mode entangled states based on cascaded four-wave mixing (FWM) process. The internal entanglement characteristics are studied by using the positivity under partial transposition criterion and eigenmode decomposition. In addition, the output entangled states are reconstructed and optimized by adjusting the relative phase of balanced homodyne detection and postprocessing the signal noise, and finally three four-mode cluster states with different structures are generated. Such a method can effectively reduce the excess noise induced by finite squeezing. Our theoretical results provide a reliable way of generating scalable continuous variable cluster states based on FWM process in atomic ensemble.

Accurate Evaluation of Cascaded Four-Wave Mixing Products Generation in Fiber with Optical Feedback Based on Multilayer Perceptronaccurate Evaluation of Cascaded Four-Wave Mixing Products Generation in Fiber with Optical Feedback Based on Multilayer Perceptron

Accurate Evaluation of Cascaded Four-Wave Mixing Products Generation in Fiber with Optical Feedback Based on Multilayer Perceptronaccurate Evaluation of Cascaded Four-Wave Mixing Products Generation in Fiber with Optical Feedback Based on Multilayer Perceptron

Continuously spacing-tunable multi-wavelength single-frequency fiber laser based on cascaded four-wave mixing at 1.06 μm

A continuously spacing-tunable multi-wavelength single-frequency fiber laser (MW-SFFL) at 1.06 μm is investigated based on cascaded four-wave mixing (CFWM) in a high-nonlinearity photonic crystal fiber (HN-PCF). By using two separate wavelength-tunable continuous-wave (CW) SFFLs for pumping the HN-PCF, the MW-SFFL with up to ten stable wavelengths is generated under a total pump power of 890 mW. Furthermore, when the wavelength and the power of pump lasers are appropriately manipulated, the wavelength spaces of the MW-SFFL can be tuned freely within 166 pm and the numbers of wavelengths can be controlled to 4, 6, 8, and 10, respectively. To our knowledge, it is demonstrated for the first time that the MW-SFFL based on CFWM at 1.0 μm band are directly excited by CW SFFLs.

Widely linewidth tunable lasers through cascaded four-wave mixing based phase modulation amplification

We demonstrate wide-range linewidth-tuning of a narrow-linewidth laser in the C-band up to 40 GHz through cascaded four-wave mixing (CFWM) based phase modulation amplification. Stimulated Brillouin scattering (SBS) severely limits the power scaling of narrow-linewidth lasers. Continuous tuning of the linewidth or temporal coherence of the laser to mitigate SBS is conventionally achieved through external phase modulation with white noise or other RF waveforms. However, the range of linewidth tuning is limited by the bandwidth and power of the electro-optic modulator. We overcome this through the use of FWM as a linewidth multiplier. To achieve linewidth multiplication, two tunable pumps line-broadened in electro-optic phase modulators with white noise are power scaled and propagated through highly nonlinear fiber. We achieve linewidth tuning up to ∼4 GHz using control of the noise waveform, while CFWM achieves a 10× multiplication of linewidth up to 40 GHz at a fixed wavelength. Linewidth tuning can be further scaled through power scaling or cascading multiple nonlinear stages. The proposed technique would be useful in nonlinearity control in narrow-linewidth laser amplifiers, high-resolution optical imaging, LIDAR, and infrared spectroscopy.

Generation of tunable ultraviolet femtosecond pulse in MgO crystal by cascaded four wave mixing

Ultraviolet femtosecond laser pulse is an important tool in studying ultrafast chemical and physical processes. Realizing broadband ultraviolet laser pluses with a wide tunable range would significantly facilitate the study of ultrafast processes. As an effective and convenient method, the cascaded four-wave mixing (CFWM) has been widely adopted to generate broadband and tunable ultraviolet femtosecond laser pulses. In this work, we carry out CFWM in MgO crystal by using two 400-nm pulses to generate tunable ultraviolet femtosecond pulse. The MgO crystal is chosen due to its high third-order nonlinear susceptibility, large band gap and high transmittance in the ultraviolet region. In the experiment, nine frequency up-converted and five frequency down-converted sidebands are observed. The measured wavelength and scattering angle of each sideband are consistent with the CFWM theory predictions. The wavelength range of the sidebands covers 350–450 nm. The total conversion efficiency of the ultraviolet sidebands is 1.2%, which is higher than the reported values with visible/near infrared driven lasers. Meanwhile, the spectra of the high-order sidebands present a Gaussian profile and can support a Fourier-transform-limited pulse duration of less than 50 fs. Besides, the central wavelengths of the sidebands can be effectively tuned by adjusting the time-delay between the two pre-chirped pump pulses. Our study provides an efficient and convenient scheme to generate short ultraviolet femtosecond pulses with a wide tunable range.

Ultrafast 1 MHz vacuum-ultraviolet source via highly cascaded harmonic generation in negative-curvature hollow-core fibers

Vacuum-ultraviolet (VUV) light is critical for the study of molecules and materials, but the generation of femtosecond pulses in the VUV region at high repetition rates has proven difficult. Here we demonstrate the efficient generation of VUV light at megahertz repetition rates using highly cascaded four-wave mixing processes in a negative-curvature hollow-core fiber. Both even- and odd-order harmonics are generated up to the 15th harmonic (69 nm, 18.0 eV), with high energy resolution of∼40meV. In contrast to direct high harmonic generation, this highly cascaded harmonic generation process requires lower peak intensity and therefore can operate at higher repetition rates, driven by a robust∼10Wfiber-laser system in a compact setup. Additionally, we present numerical simulations that explore the fundamental capabilities and spatiotemporal dynamics of highly cascaded harmonic generation. This VUV source can enhance the capabilities of spectroscopies of molecular and quantum materials, such as photoionization mass spectrometry and time-, angle-, and spin-resolved photoemission.

Multicolor concentric annular ultrafast vector beams.

Novel multicolor concentric annular ultrafast vector beams (MUCAU-VB) are firstly generated simply by using cascaded four-wave mixing (CFWM) in a glass plate pumped by two intense vector femtosecond pulses. A proof-of-principle experiment shows that up to 10 frequency up-conversion concentric annular radially polarized sidebands are obtained simultaneously based on CFWM process, where the spectra range of the first 7 order sidebands extending from 545 nm to 725 nm. The results prove the polarization transfer property from the pump beam to the signal beams even in the CFWM, a third-order optical parametric process. The pulse duration of the first order sideband is measured to be 74 fs which is according with those of two input beams. These novel MUCAU-VB, which are manipulated in temporal, spectral, spatial domain and polarization state simultaneously, are expected to apply in wide fields, such as manipulating particles and multicolor pump-probe experiments.

Experimental characterization of multiple quantum correlated beams in two-beam pumped cascaded four-wave mixing process.

We experimentally explore the relationships between the number of multiple quantum correlated beams generated by two-beam pumped cascaded four-wave mixing (CFWM) process and the system parameters, such as the angle between the two pump beams, one-photon detuning and two-photon detuning. We find that all of three system parameters can influence the number of multiple quantum correlated beams. Under the optimal system parameters, we can observe the emission of up to 14 quantum correlated beams with the intensity-difference squeezing of -6.29 ± 0.20 dB (-7.93 ± 0.64 dB after accounting for losses) from such CFWM scheme. Our results may find potential applications in building multi-user quantum network and multi-parameter quantum metrology.

Cross-referenced deadband-free microwave frequency measurement with cascaded-four-wave-mixing-based photonic harmonic down-conversion.

A cross-referenced and deadband-free method with photonic harmonic down-conversion is proposed for microwave frequency measurement based on cascaded-four-wave-mixing (CFWM) in semiconductor optical amplifiers. The proposed method enables ultra-wide and accurate frequency measurement with low-frequency spectrum detection, and at the same time achieves deadband-free and multi-tone frequency measurement by cross-referenced frequency discrimination. For a proof of concept, microwave signal measurement is experimentally demonstrated up to the 40 GHz frequency range with an 0.2-MHz measurement error. The frequency measurement features ease of configuration by only changing the low-frequency electrical local oscillators of the CFWM-based photonic harmonic down-converter.

Generation of high-energy clean multicolored ultrashort pulses and their application in single-shot temporal contrast measurement.

We demonstrate the generation of 100-μJ-level multicolored femtosecond pulses based on a single-stage cascaded four-wave mixing (CFWM) process in a thin glass plate by using cylinder lenses. The generated high-energy CFWM signals can shift the central wavelength and have well-enhanced temporal contrast because of the third-order nonlinear process. They are innovatively used as clean sampling pulses of a cross-correlator for single-shot temporal contrast measurement. With a simple homemade setup, the proof-of-principle experimental results demonstrate the single-shot cross-correlator with dynamic range of 1010, temporal resolution of about 160 fs and temporal window of 50 ps. To the best of our knowledge, this is the first demonstration in which both the dynamic range and the temporal resolution of a single-shot temporal contrast measurement are comparable to those of a commercial delay-scanning cross-correlator.

Quantum manipulation of entanglement enhancement in cascaded four-wave-mixing process

Entanglement manipulation in various systems is one of the important problems in quantum information science. In this paper, the phase sensitivity and entanglement enhancement of the cascade four-wave mixing of hot atomic steam are studied. The results show that the quantum entanglement of the probe light and the conjugate light output at the second level of the cascade four-wave mixing process is significantly stronger than that at the first level, and the maximum increment can reach more than 5 dB, and the perfect entanglement can be achieved by increasing the intensity factor. The relations of quantum correlation type and the size of the entanglement with the pump phase and the nonlinear intensity factor are also discussed in this work. The results show that because of the enhancement of entanglement and the sensitivity of entanglement type to pump phase, the light field noise characteristics can be changed by controlling the phase and intensity factors thus realize the enhancement of entanglement between the probe and coupling light and the quantum manipulation of entanglement extent and quantum entanglement type. The theoretical study is of important significance for guiding the experimental implementation of optical parameter manipulation of entanglement enhancement, compression angle and compression degree of two-mode compression state.

Two-beam pumped cascaded four-wave-mixing process for producing multiple-beam quantum correlation

We propose a two-beam pumped cascaded four-wave-mixing (CFWM) scheme with a double-$\mathrm{\ensuremath{\Lambda}}$ energy-level configuration in $^{85}\mathrm{Rb}$ vapor cell and experimentally observe the emission of up to 10 quantum correlated beams from such CFWM scheme. During this process, the seed beam is amplified; four new signal beams and five idler beams are generated. The 10 beams show strong quantum correlation which is characterized by the intensity-difference squeezing of about $\ensuremath{-}6.7\ifmmode\pm\else\textpm\fi{}0.3$ dB. Then, by altering the angle between the two pump beams, we observe the notable transition of the number of the output beams from 10 to eight, and even to six. We find that both the number of the output quantum correlated beams and their degree of quantum correlation from such two-beam pumped CFWM scheme increase with the decrease of the angle between the two pump beams. Such system may find potential applications in quantum information and quantum metrology.