Gain Of Optical Parametric Amplifier Research Articles

Controlling Remote Entanglement and One‐Way Steering Via a Squeezed Vacuum Field and an Optical Parametric Amplifier

AbstractA scheme is proposed for generating remote entanglement and one‐way Einstein‐Podolsky‐Rosen (EPR) steering between two mechanical resonators in a cavity optomechanical system. Both mechanical resonators are coupled to a common cavity, which contains an optical parametric amplifier (OPA) and is driven by a squeezed vacuum field. The entanglement and EPR steering can be generated by the squeezed vacuum field and significantly enhanced by the gain of OPA. By manipulating the ratio of two effective optomechanical coupling strengths, the asymmetric EPR steering with excellent controllability on the direction, even the one‐way EPR steering can be achieved. Moreover, both the squeezed vacuum field and the OPA can effectively enhance the robustness of EPR steering against the environment temperature, and the temperature‐dependent one‐way EPR steering is explored. This work paves the way toward generating macroscopic mechanical entanglement and EPR steering with potential applications in quantum information processing.

Controlling double optomechanically induced transparency and slow/fast light in an electro-optomechanical system via an optical parametric amplifier

We investigate tunable double optomechanically induced transparency and slow/fast phenomena in a hybrid electro-optomechanical system. The hybrid system consists of an optical cavity with an optical parametric amplifier (OPA) and two charged mechanical resonators. The double optomechanical induce transparency can be exhibited by manipulating the coupling parameters of the electro-optomechanical system. Specifically, the number of transparent points and the width of transparent windows increase with an increase in the coupling constant. Furthermore, the phenomenon of double transparency is strongly influenced by the parametric gain of OPA and by the Coulomb interaction between the two mechanical oscillators. It is found that the larger parametric gain and Coulomb coupling induce an increasing width of transparency windows. Moreover, we study the slow/fast light effect associated with the rapid phase change of the transmission of probe field. Our approach provides a great flexibility for controlling double induced transparency, and has potential applications in optical information storage and optical communication.

Optical spring effect enhanced by optical parametric amplifier

We experimentally demonstrate that the optical spring effect can be modified using an optical parametric amplifier in an opto-mechanical cavity. The theoretical analysis shows that both the gain and phase of the optical parametric amplifier can modify the frequency of a mechanical resonator in an opto-mechanical cavity. This modification could be used to tune the frequency of peak sensitivity of gravitational wave detectors. The experimental results show a factor of 1.2 ± 0.8 increase in mechanical resonator frequency shift induced by optical spring by tuning the optical parametric amplifier gain.

Normal-mode splitting in an optomechanical system enhanced by an optical parametric amplifier and coherent feedback

Normal-mode splitting (NMS) is an evident signature of strong coupling interactions for observing quantum phenomena, such as optomechanical squeezing and entanglement. In the previous literature, optical parametric amplifier (OPA) and coherent feedback are independently proposed to enhance the NMS. Here, we combine OPA and coherent feedback into a single optomechanical system to enhance the NMS. Controllable parameters, such as input optical power, OPA gain and phase, coherent feedback strength, are varied to observe NMS variations. In particular, we consider positive and negative feedback in terms of the amplitude reflectivity of the beam splitter for coherent feedback. The NMS appears mostly with the positive coherent feedback rather than the negative. Furthermore, the largest mode separation occurs at an OPA phase of approximately rather than zero because the effective cavity detuning changes the effective intracavity round-trip phase, and therefore changes the OPA amplification/deamplification condition. The results indicate that the interplay between OPA and coherent feedback can enhance the NMS with more controllable parameter freedoms. This scheme provides a promising way to increase the optomechanical coupling strength, thereby having potential applications in the ground state cooling of a mechanical oscillator, the preparation of optomechanical quantum states, and the sensitive detection of a weak force.

Generation of second-order sideband and slow-fast light effects in a PT-symmetric optomechanical system

We theoretically study the second-order sideband generation and slow-fast light effects in a parity-time (PT) symmetric optomechanical system, which consists of an active cavity and a passive cavity containing optical parametric amplifier (OPA). Compared to the double-passive nonlinear system, we find that the second-order sideband efficiency can be significantly enhanced by the tunneling strength in the PT-symmetric system with OPA. The flexible manipulation of the second-order generation also can be realized by modulating OPA gain and phase. Moreover, the fast and slow light effects in the optomechanical system are discussed. When the tunneling strength J=3κ1, the time of the second-order sideband group delay can be effectively prolonged in a PT-symmetric cavity in the presence of OPA. The results may have some guidance for the enhancement of second-order sideband efficiency, which has potential applications in optical communication and storage.

Nonreciprocal unconventional photon blockade in a driven dissipative cavity with parametric amplification

In this paper, we show that nonreciprocal unconventional photon blockade can be observed in a spinning cavity immersed in a degenerate optical parametric amplifier (OPA) driven by the laser driving with weak Kerr nonlinearities through the Fizeau drag. We analytically derive the optimal conditions for strong antibunching, which are in good agreement with those obtained by numerical simulations. Under the weak driving condition, we discuss the physical origins of the nonreciprocal unconventional photon blockade, which originates from the destructive interference between different paths from the ground state to two-photon states by driving the device from the left side. While the quantum interference paths are broken when the device is driven from the right side, which leads to the occurring of the photon bunching. Moreover, we extend the above results to the general non-Markovian regimes, in which the cavity couples with a thermal reservoir consisting of collection of infinite oscillators (bosonic photonic modes). We show nonreciprocal unconventional photon blockade exhibits a transition from the non-Markovian to Markovian regimes by controlling environmental spectral width regardless of the weakness of OPA gain and driving field.

Manifestation of classical nonlinear dynamics in optomechanical entanglement with a parametric amplifier

Cavity optomechanical system involving an optical parametric amplifier (OPA) can exhibit rich classical and quantum dynamical behaviors. By simply modulating the frequency of the laser pumping the OPA, we find two interesting parameter regimes, with one of them enabling to study quantum-classical correspondence in system dynamics, while there exist no classical counterparts of the quantum features for the other. For the former regime, as the parametric gain of OPA increases to a critical value, the classical dynamics of the optical or mechanical modes can experience a transition from the regular periodic oscillation to period-doubling motion, in which cases the light-mechanical entanglement can be well studied by the logarithm negativity and can manifest the dynamical transition in the classical nonlinear dynamics. Moreover, the optomechanical entanglement shows a second-order transition characteristic at the critical parametric gain. For the latter regime, the kind of normal mode splitting comes up in the laser detuning dependence of optomechanical entanglement, which is induced by the squeezing of the optical and mechanical hybrid modes and finds no classical correspondence. The OPA assisted optomechanical systems therefore offer a simple way to study and exploit quantum manifestations of classical nonlinear dynamics.

Generation and enhancement of sum sideband in a quadratically coupled optomechanical system with parametric interactions.

We investigate theoretically the generation and enhancement of sum sideband in a quadratically coupled optomechanical system with parametric interactions. It is shown that the generation of frequency components at the sum sideband stems from the nonlinear optomechanical interactions via two-phonon processes in the quadratically coupled optomechanical system, while an optical parametric amplifier (OPA) inside the system can considerably improve the sum sideband generation (SSG). The dependence of SSG on the system parameters, including the power of the control field, the frequency detuning of the probe fields and the nonlinear gain of OPA are analyzed in detail. Our analytic calculation indicates that the SSG can be obtained even under weak driven fields and greatly enhanced via meeting the matching conditions. The effect of SSG may have potential applications for achieving measurement of electric charge (or other weak forces) with higher precision and on-chip manipulation of light propagation.

Tunable unconventional phonon blockade in Fabry-Perot cavity and optical parametric amplifier composite system

In this paper, we present a scheme to realize an unconventional photon blockade effect in a Fabry-Perot cavity and optical parametric amplifier (OPA) composite system. The system includes a tunable phase of complex driving strength, the second-order correlation function is used to describe the photon statistical properties. The numerical simulation of the photon blockade effect is conducted with different parameters. Our calculations show that the unconventional photon blockade effect can be controlled by the tunable phase of complex driving strength. Under the weak driving condition, the exact optimal conditions for strong photon anti-bunching are analytically derived (i.e. the optimal nonlinear gain of optical parametric amplifier and the phase of the field driving for the strong photon anti-bunching are obtained), and obtain the analytic calculations of the second-order correlation function. Under the optimal conditions, we perform a numerical simulation with different parameters. The optimal conditions for strong photon anti-bunching are found by analytic calculations, which are in good agreement with the numerical results. The results provide a platform for coherently operating the photon blockade and have potential applications in quantum information processing and quantum optical devices.

Scheme for enhancing quadripartite entangled optical modes from an opto-mechanical system

Multipartite entanglement is a key resource for quantum information processing and quantum communication. We show that the robust entanglement among four filtered output optical modes can be achieved when there is a nonlinear crystal inside an optomechanical cavity. The optical parametric amplifier (OPA) gives rise to single-mode squeezing of the cavity modes; therefore, the entanglement among four output optical modes can be enhanced remarkably. Furthermore, the degree of quadripartite entanglement is influenced by the nonlinear gain of OPA and bandwidth of the filters. Large entanglement can be obtained by optimizing the filter functions, which is important for utilizing entangled light beams more efficiently in real experiments. This kind of multipartite entanglement will be useful and valuable in the area of quantum communication networks.

Target Detection of Quantum Illumination Receiver Based on Photon-subtracted Entanglement State

We theoretically propose a quantum illumination receiver based on the ideal photon-subtracted two-mode squeezed state (PSTMSS) to efficiently detect the noise-hidden target. This receiver is generated by applying an optical parametric amplifier (OPA) to the cross correlation detection. With analyzing the output performance, it is found that OPA as a preposition technology of the receiver can contribute to the PSTMSS by significantly reducing the error probability than that of the general two-mode squeezed state (TMSS). Comparing with TMSS, the signal-to-noise ratio of quantum illumination based on ideal PSTMSS and OPA is improved more than 4 dB under an optimal gain of OPA. This work may provide a potential improvement in the application of accurate target detection when two kinds of resource have the identical real squeezing parameter.

Optimizing bandwidth of fiber optical parametric amplifier with different combinations of higher-order dispersion coefficient signs

This paper investigates the influence of different combinations of second-order (β2 ), fourth-order (β4 ) and sixth-order (β6 ) dispersion coefficient signs (negativity/positivity) to the fiber optical parametric amplifier gain performance. The numerical simulation has exploited the fourth-order Runge-Kutta method to solve the coupled amplitude equations which basically represent the parametric process of four-wave mixing. In the normal regime at which β2 is positive, the fiber optical parametric amplifier exhibits a poor gain spectrum and it is well performed once the pump is presumed to be in anomalous regime i.e. β2 is negative. The effect of β4 is significant when the signal wavelength is further from the pump wavelength and a wide amplification bandwidth is produced when the fiber have positive β4 in the anomalous regime. As for β6 , unfortunately in this simulation its influences are hardly can be seen probably because of its small value regardless its sign, but, from phase-mismatch equation it is shown that its impact is prominent when the signal is positioned way far from the pump. All in all, this shown that the signs combination of the higher-order dispersion coefficients are significant in order to optimize the FOPA amplification bandwidth.

Measurement of two-mode squeezing with photon number resolving multipixel detectors

The measurement of the two-mode squeezed vacuum generated in an optical parametric amplifier (OPA) was performed with photon number resolving multipixel photon counters (MPPCs). Implementation of the MPPCs allows for the observation of noise reduction in a broad dynamic range of the OPA gain, which is inaccessible with standard single photon avalanche photodetectors.

Optimization of Raman-Assisted Fiber Optical Parametric Amplifier Gain

We studied the gain of Raman-assisted fiber optical parametric amplifiers (RA-FOPAs) both theoretically and experimentally. We investigated the relationship between the overall gain and different combinations of Raman and parametric pump powers using contour maps. We derived a normalized phase-matched model to determine the general behavior the peak gains of RA-FOPAs operating in the small signal region. The contour maps of the combined gain enhancement can be used to optimize both indirect and direct Raman gain of the signal/idler in RA-FOPAs. We showed that, in a given fiber, it is possible to optimize the Raman and parametric pump powers in RA-FOPAs for high gain and high efficiency.

Multiple-wavelength conversion with gain by a high-repetition-rate pulsed-pump fiber OPA

The authors propose and demonstrate a novel multiple-wavelength converter with gain, based on a pulsed-pump fiber optical parametric amplifier (OPA). It generates multiple replicas of the signal, as well as spectrally inverted versions. The device is modeled by using quasi-steady-state OPA gain equations, as well as by the split-step Fourier method. Predicted conversion gains of up to 20 dB have been confirmed by experiments. A 10-Gb/s nonreturn-to-zero (NRZ) input signal was converted into several replicas, with penalties ranging from 0.26 to 1.24 dB for frequency shifts of /spl plusmn/k/spl times/100 GHz (k=1, 2, 3, 4).

Pump-to-signal transfer of low-frequency intensity modulation in fiber optical parametric amplifiers

This paper describes the theoretical and experimental investigation of the transfer of low-frequency intensity modulation (IM) from pump to signal in fiber optical parametric amplifiers (OPAs). It is first established that low-frequency IM of the pump remains unchanged over the length of the amplifier in spite of the presence of parametric gain. The pump-power dependence of the OPA gain is then used to calculate the instantaneous effect of pump IM on the signal and idler output powers. These calculations are performed for both one- and two-pump OPAs. The main predictions are that 1) the ratio /spl rho/ of the signal intensity modulation depth to that of the pump varies across the OPA gain spectrum and 2) for a 20-dB gain, /spl rho/ can exceed 10 at some wavelengths, which indicates that this effect can be detrimental. Experiments have been performed to verify these predictions. Using sinusoidal IM of the pump, the resulting amplified signal IM was measured, and the experimental results were found to be in good agreement with the theoretical predictions.

Wide-Band Tuning of the Gain Spectra of One-Pump Fiber Optical Parametric Amplifiers

By suitably choosing the fiber properties, and by tuning the pump wavelength near the fiber zero-dispersion wavelength, one can in principle generate a wide variety of one-pump fiber optical parametric amplifier gain spectra. These can range from a very wide single region to two symmetric narrow gain regions far away from the pump. We have experimentally verified these predictions. With a highly nonlinear fiber, we have inferred the existence of gain over a single 400-nm region and measured a maximum on-off gain of 65 dB. With a common dispersion-shifted fiber, we have obtained tunable gain regions less than 1 nm wide, up to 200 nm from the pump; we have also shifted these by several nanometers by lowering the fiber temperature to 0/spl deg/C.

200-nm-bandwidth fiber optical amplifier combining parametric and Raman gain

Theory shows that the gain bandwidth of a one-pump fiber optical parametric amplifier (OPA) using highly nonlinear fiber (HNLF) could be more than 200 nm. Under these circumstances, the OPA gain would overlap the pump-induced Raman gain. We have studied the combined effects of OPA and Raman gain theoretically and experimentally. The experimental results demonstrate a 200-nm bandwidth from a single fiber-optical amplifier and also verify that the influence of the Raman effect is relatively small, as predicted by the theory.

Automatic time delay optimization between the pump and seed pulses of a broadly tunable femtosecond optical parametric amplifier

We propose a scheme for optimizing the time delay between the pump and seed pulses of an optical parametric amplifier (OPA) over a large spectral range. The efficiency of this method is demonstrated for a femtosecond BBO parametric amplifier seeded with a white-light continuum pulse. The error signal used for intensity stabilization results from a modulation of the temporal delay between the pump and the continuum pulses and phase-sensitive detection of the amplified signal. It allows us to lock the delay to the position that maximizes the OPA gain.