Analysis of quantum noise in a singly resonant nondegenerate optical parametric oscillator

We have analyzed the evolution of quantum operators in a three-wave mixing process by using the nonlinear polarization driven wave equations and linearization of the quantum operators. We have theoretically shown that a nondegenerate optical parametric amplifier can generate amplitude-squeezed light when operated in the backconversion regime. Furthermore, a nondegenerate optical parametric oscillator, where only the signal wave is resonant, is proved to generate amplitude-squeezed light when the pump intensity is above the value at which 100% photon conversion efficiency is achieved. The calculated limit for amplitude-squeezing in this case is 3 d B.     

Compact efficient eye-safe intracavity optical parametric oscillator with a shared cavity configuration

We present a compact efficient eye-safe intracavity optical parametric oscillator pumped by a passively Q-switched Nd:YAG laser in a shared cavity configuration. A signal pulse of 3.3 mJ energy at a 1573 nm wavelength with a peak power of 150 kW was achieved. The effective conversion efficiency with respective to the optimized 1064 nm Q-switched pulse energy was as high as 51%.     

Entanglement generated in a nanomechanical oscillator system

We consider a Fabry–Perot cavity with one fixed mirror and a movable perfectly reflecting mirror. Applying a linearised fluctuation analysis, we derive the quantum fluctuations and correlation matrix between the cavity and nanomechanical oscillator. We investigate the continuous-variable (CV) entanglement and squeezing between the cavity and nanomechanical oscillator. It is found that high intensity of entanglement and squeezing between the cavity and nanomechanical oscillator can be achieved.     

Enhanced entanglement in a non-degenerate four-level atom with a parametric oscillator

We discuss the generation and evolution of a macroscopic entanglement light with a subthreshold non-degenerate parametric oscillator, coupled to a vacuum reservoir. The four-level atoms driven by two classical fields interact with the parametric oscillator. The master equation for the cavity modes of the scheme is derived and analyzed, the entanglement properties of the two-mode light generated by this scheme inside and outside the cavity is studied. We show that the light produced by this system is strongly entangled with time evolution inside and outside a cavity.     

High-efficiency mid-infrared ZnGeP2 optical parametric oscillator in a multimode-pumped tandem optical parametric oscillator

We demonstrate a high-efficiency ZnGeP(2) optical parametric oscillator (OPO) pumped by another KTP OPO in a multimode-pumped tandem OPO configuration. The maximum optical-to-optical and slope efficiencies were 32% and 42.5%, respectively. Our setup also provides tunable multiband radiation in the 2.03-2.32-mum range and the 2.9-6.2-mum range simultaneously.     

Photoacoustic measurement of methane concentrations with a compact pulsed optical parametric oscillator

A pulsed periodically poled lithium niobate optical parametric oscillator operating in a cavity with a grazing-incidence grating configuration was used for sensitive and precise measurement of trace quantities of methane in nitrogen by photoacoustic spectroscopy with a novel differential photoacoustic detector. A sensitivity of 1.2 parts in 10(9) by volume of methane was obtained in direct calibration measurements (not extrapolated). With this apparatus, in situ measurement of the methane concentration in ambient air under atmospheric conditions was demonstrated.     

Multimodal coherent anti-Stokes Raman spectroscopic imaging with a fiber optical parametric oscillator

We report on multimodal coherent anti-Stokes Raman scattering (CARS) imaging with a source composed of a femtosecond fiber laser and a photonic crystal fiber (PCF)-based optical parametric oscillator (FOPO). By switching between two PCFs with different zero dispersion wavelengths, a tunable signal beam from the FOPO covering the range from 840 to 930 nm was produced. By combining the femtosecond fiber laser and the FOPO output, simultaneous CARS imaging of a myelin sheath and two-photon excitation fluorescence imaging of a labeled axons in rat spinal cord have been demonstrated at the speed of 20 μs per pixel.     

Entanglement sudden birth and sudden death in a system of two distant atoms coupled via an optical element

An investigation is reported of the collective effects and the dynamics of atom–atom entanglement in a system of two distant two-level atoms which are coupled via an optical element. In the system under consideration, the two atoms, which are trapped in the foci of a lens, are coupled to a common environment being in the vacuum state and they emit photons spontaneously. A fraction of the emitted photons from each atom is thus focused on the position of the other atom. The presence of optical element between two distant atoms leads to the occurrence of delayed collective effects, such as delayed dipole–dipole interaction and delayed collective spontaneous emission, which play the crucial role in the dynamical behaviour of the entanglement. We discuss the phenomena of entanglement sudden birth, entanglement sudden death, and revival of entanglement for both cases of initial one-photon and initial two-photon unentangled atomic states. We show that the evolution of the entanglement is sensitive not only to the interatomic distance but also to the initial state of the system as well as to the properties of the optical element.     

Single-mode, tunable output from a midwave-infrared-seeded optical parametric oscillator system

We have built a coupled master oscillator and a slave oscillator optical parametric oscillator (OPO) system that provides single-frequency, pulsed radiation in the midwave infrared (MWIR). The direct-diode-pumped master OPO provided narrow-band (<6-MHz, instrument-limited), tunable MWIR cw radiation that was used to seed a higher-peak-power pulsed slave OPO. When seeded directly at the MWIR idler, the pulsed output of the slave OPO was constrained to oscillate on a single longitudinal mode even though the slave OPO is pumped by a multilongitudinal-mode laser source. The linewidth of the pulsed output has been measured to be <220 MHz (instrument limited), which is well suited for coherent differential absorption lidar applications.     

The tripartite entanglement in a phase-mismatched frequency non-degenerated optical parametric amplifier

We present an analytical solution for Fokker–Planck equation of phase-mismatched frequency non-degenerated optical parametric amplifier (FNOPA). We investigate the continuous-variable (CV) tripartite entanglement characteristic of FNOPA working at phase-matched and phase-mismatched condition. From below threshold to above threshold, we numerically calculate the dependence of CV tripartite entanglement on relative loss parameter η and phase-mismatched factor Δω. The larger η and the smaller Δω can bring a good entanglement.     

Tunable single-mode operation of a pulsed optical parametric oscillator pumped by a multimode laser

High-quality single-longitudinal-mode (SLM) tunable signal radiation is generated by a pulsed optical parametric oscillator (OPO) pumped by a compact, inexpensive multimode laser. The OPO is based on periodically poled lithium niobate (PPLN) in a ring cavity that is injection seeded at its resonated signal wavelength by a single-mode tunable diode laser. Accurate control of the OPO cavity length and crystal temperature ensures a continuously tunable SLM signal output frequency range of >7.5 THz (>250 cm(-1)); the corresponding idler output remains multimode. High-resolution molecular spectra are recorded to verify OPO performance at wavelengths of ~1.55 mum. The observed signal optical bandwidth of 相似文献   

Limited efficiency of a silver selenogallate optical parametric oscillator caused by two-photon absorption

The nonresonant two-photon absorption (TPA) coefficient in silver selenogallate (AgGaSe(2)) crystals was measured for both ordinary and extraordinary polarizations in the 1300-1600-nm wavelength range. We found a cutoff wavelength for the TPA at between 1400 and 1500 nm, which corresponds to half of the bandgap energy of the AgGaSe(2) crystal. Below the cutoff wavelength we measured the TPA coefficient to be approximately 0.035 cm/MW for the extraordinary polarization and two to three times lower for the ordinary polarization. We compared the AgGaSe(2) samples from two manufacturers and observed a factor of 2 difference in the TPA coefficients. Because of the high TPA, the 1.32-mum pumped AgGaSe(2) optical parametric oscillator conversion efficiency was clipped at a low level.     

Entanglement swapping with non-Gaussian resources

We investigate the entanglement swapping of non-Gaussian states, including squeezed number states, two-mode photon-added states, and two-mode photon-subtracted squeezed states and analyze the entanglement of the swapped states by adopting logarithmic negativity as the measure of entanglement. Furthermore, we examine the fidelity of teleportation protocols for different input states where the swapped states serve as the quantum channel. All these results are compared with that obtained in the case of Gaussian two-mode squeezed vacuum.     

Characterization of a periodically poled lithium niobate optical parametric oscillator pumped by a Bessel beam

Abstract

A Bessel beam pumped periodically poled lithium niobate optical parametric oscillator has been characterized. A slope efficiency of 5.4 ± 0.1% was obtained and a threshold pulse energy of 472 ± 12 μJ was measured, which corresponds to a threshold fluence of 0.207 ± 0.005 J cm^?2. The signal output was tuned over ～20 nm by changing the crystal temperature by 50°C. The FWHM bandwidth at each temperature was observed to be 0.3 ± 0.1 nm at each wavelength. The beam profiles of the Bessel pump and Gaussian signal beams were studied in both the near and far field. A beam divergence of 1.14 ± 0.02 mrad was measured.     

Tunable continuous-wave doubly resonant optical parametric oscillator by use of a semimonolithic KTP crystal

A temperature-tuned continuous-wave doubly resonant optical parametric oscillator (OPO) consisting of a semimonolithic KTP crystal and a concave mirror has been designed and built. Under single-axial-mode-pair operation, we obtained a combined output power of the signal and idler light fields up to 365 mW at a pump power of 680 mW. The output wavelength of the OPO can be temperature tuned by as much as 9 nm. We achieved 2.8-GHz continuous frequency tuning of the OPO by tuning the pump laser frequency.     

Improved scanning range for coherent anti-stokes Raman spectroscopy using a tunable optical parametric oscillator

Coherent anti-Stokes Raman spectroscopy (CARS) is a well-known form of nonlinear spectroscopy that has been used for a wide range of specialized quantitative applications. From an analytical chemist's point of view, however, conventional CARS is impractical as a tool for qualitative and quantitative analyses because the scan range is too short to produce complete vibrational spectra. This paper introduces a new technique, synchronously scanned optical parametric oscillator (OPO) CARS, that improves the potential for using nonlinear spectroscopy as an analytical technique in both gas- and condensed-phase samples. First, it uses a broadly tunable OPO to increase the scan range. Second, phase matching problems that limit scans in condensed-phase CARS are reduced by using both the signal and the idler beams in a synchronous scanning manner. Finally, this synchronous scanning method generates an output signal that remains fixed at a single wavelength (single-wavelength detection). Advantages of single-wavelength detection include reduction of stray light, simplicity, and elimination of the need for wavelength calibration of the detection optics. Results are presented on neat and mixed samples in gas and condensed phases.     

Nearly diffraction-limited signal generated by a lower beam-quality pump in an optical parametric oscillator

The beam quality of an optical parametric oscillator (OPO) within a singly resonant, confocal-positive branch unstable resonator is investigated. Resonator configurations have been found in which the beam quality of the outgoing signal exceeds the beam quality of the pump. Cavity magnification and pump-pulse duration are found to determine the signal beam quality. It is shown that signal M2 decreases with increasing pump-pulse duration for a given cavity magnification. In an experimental demonstration of a LiNbO3 OPO within an unstable resonator, pumped by a multitransversal mode beam, a signal beam with an almost-single transversal mode has been generated, whereas the multitransversal mode behavior of the pump beam is projected on the idler beam.     

Characterization of a CH planar laser-induced fluorescence imaging system using a kHz-rate multimode-pumped optical parametric oscillator

The performance characteristics of a new CH planar laser-induced fluorescence (PLIF) imaging system composed of a kHz-rate multimode-pumped optical parametric oscillator (OPO) and high-speed intensified CMOS camera are investigated in laminar and turbulent CH4-H2-air flames. A multi-channel Nd:YAG cluster that produces up to 225 mJ at 355 nm with multiple-pulse spacing of 100 μs (corresponding to 10 kHz) is used to pump an OPO to produce up to 6 mJ at 431 nm for direct excitation of the A-X (0, 0) band of the CH radical. Single-shot signal-to-noise ratios of 82:1 and 7.5:1 are recorded in laminar premixed flames relative to noise in the background and within the flame layer, respectively. The spatial resolution and image quality are sufficient to accurately measure the CH layer thickness of ~0.4 mm while imaging the detailed evolution of turbulent flame structures over a 20 mm span. Background interferences due to polycyclic-aromatic hydrocarbons and Rayleigh scattering are minimized and, along with signal linearity, allow semi-quantitative analysis of CH signals on a shot-to-shot basis. The effects of design features, such as cavity finesse and passive injection seeding, on conversion efficiency, stability, and linewidth of the OPO output are also discussed.