Aki Torii, Kosuke Shibata, Yujiro Eto, Takuya Hirano
Optics Express 30(15) 26120-26120 2022年7月18日 査読有り
We report on the waveguide-based generation of pulsed squeezed light at 795 nm, suitable for quantum enhanced measurements with rubidium atoms. Pulsed ultraviolet second harmonic light with a power of more than 400 mW is produced using a periodically poled LiNbO3 (PPLN) waveguide and is injected into another PPLN waveguide to generate quadrature squeezing. We find that the phase of the second harmonic pulse is shifted within a pulse, and we attribute the shift to heating due to blue-light induced infrared absorption (BLIIRA) from a comparison between the experiment and a numerical simulation. A squeezing level of −1.5(1) dB is observed in homodyne detection when we apply a linear phase shift to the local oscillator. The experiment and simulation imply that the squeezing level can be further improved by reducing BLIIRA.
Japanese Journal of Applied Physics 60(5) 2021年5月 査読有り
Second-harmonic generation (SHG) using periodically poled material in the high-conversion regime is investigated experimentally and theoretically. In the experiment, we use nanosecond pulses and periodically poled MgO:LiNbO3 waveguides with two lengths, 8.3 and 3.6 mm. In both waveguides, the conversion efficiency reaches 80% with increasing pump power and then decreases. The reduction in efficiency is more prominent for the long waveguide. For a peak power of the fundamental wave exceeding 140 W, stronger SHG is achieved by using the short waveguide. To understand these phenomena, we numerically investigate the effect of the cascaded nonlinear phase shift caused by the quasi-phase-matched SHG. The nonlinear phase shift induces an energy backflow to the fundamental wave even when effective phase matching is satisfied, and it greatly reduces the conversion efficiency, at the same level of power as the experiment.
Correlation measurements of the outputs of a nondegenerate optical parametric amplifier with weak coherent input light were performed. By choosing the relative phase between the input and pump light, we observed positive and negative correlation between the signal and idler photons.
A different way of producing antibunched light was experimentally demonstrated in which the production process is difficult to understand by a naive photon picture. A degenerate beam of down-converted photon pairs from a nonlinear crystal pumped by pulsed light was mixed with coherent local oscillator pulses by a beam splitter, and the intensity autocorrelation of one of the output beams was measured. It showed two-photon interference fringes as the phase difference of the two input fields was varied, and showed antibunching when the interference was destructive.
PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 33(1-3) 413-417 1996年
We investigate spectroscopic properties of cold Rb-85 atoms in a magneto-optic trap. Both the transmission and the reflection spectra of the trapped atoms are recorded. The dressed-atom picture and the density-matrix formalism are appropriatery used to explain the absorption profile around the F = 3-F' = 2,3,4 and F = 2-F' = 1 transitions. Around the trapping laser frequency, phase-conjugation signals are observed (reflectivity is about 10(-4)), which are attributed to the degenerate and nearly-degenerate four-wave mixing.
PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 33(1-3) 339-342 1996年
We find that photons from a light emitting diode injected with Poissonian electrons have super-Poissonian statistics when the differential efficiency is larger than the mean emission efficiency of the device. This result shows the limitation of a conventional theory which describes the generation of sub-Poissonian light in terms of Poisson point process.
PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 33(1-3) 413-417 1996年
We investigate spectroscopic properties of cold Rb-85 atoms in a magneto-optic trap. Both the transmission and the reflection spectra of the trapped atoms are recorded. The dressed-atom picture and the density-matrix formalism are appropriatery used to explain the absorption profile around the F = 3-F' = 2,3,4 and F = 2-F' = 1 transitions. Around the trapping laser frequency, phase-conjugation signals are observed (reflectivity is about 10(-4)), which are attributed to the degenerate and nearly-degenerate four-wave mixing.
PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 33(1-3) 339-342 1996年
We find that photons from a light emitting diode injected with Poissonian electrons have super-Poissonian statistics when the differential efficiency is larger than the mean emission efficiency of the device. This result shows the limitation of a conventional theory which describes the generation of sub-Poissonian light in terms of Poisson point process.
IEEE JOURNAL OF QUANTUM ELECTRONICS 31(12) 2236-2240 1995年12月
Weak sub-Poissonian light was generated with a high-efficiency light-emitting diode (LED). The lowest intensity of sub-Poissonian light generated in our experiment was about thousand times as small as those of previous experiments. iis an injection current to LED decreased, the mean emission efficiency lowered at room temperature and the frequency response worsened at liquid nitrogen temperature, These phenomena were interpreted in terms of trap states.
IEEE JOURNAL OF QUANTUM ELECTRONICS 31(12) 2236-2240 1995年12月
Weak sub-Poissonian light was generated with a high-efficiency light-emitting diode (LED). The lowest intensity of sub-Poissonian light generated in our experiment was about thousand times as small as those of previous experiments. iis an injection current to LED decreased, the mean emission efficiency lowered at room temperature and the frequency response worsened at liquid nitrogen temperature, These phenomena were interpreted in terms of trap states.
A two-photon coincidence counting measurement is reported of a squeezed pulse train from a parametric amplifier pumped by a mode-locked laser. The intensity correlation function at zero time delay can be determined by measuring the ratio of two types of the coincidences, the one within the same mode-locked pulse and the one among different pulses. A single mode analysis of the intensity correlation function g(2) is made to explain the experimental results. A discrepancy between the theory and the experiments due to a geometrical problem of detecting the paired photons is discussed.
A two-photon coincidence counting measurement is reported of a squeezed pulse train from a parametric amplifier pumped by a mode-locked laser. The intensity correlation function at zero time delay can be determined by measuring the ratio of two types of the coincidences, the one within the same mode-locked pulse and the one among different pulses. A single mode analysis of the intensity correlation function g(2) is made to explain the experimental results. A discrepancy between the theory and the experiments due to a geometrical problem of detecting the paired photons is discussed.
We have measured the intensity correlation of pulsed squeezed light generated by a degenerate optical parametric amplifier seeding weak coherent input signal. When the signal was deamplified, the correlation showed antibunching and the probability distribution of the photon number was sub-Poissonian, both of these being nonclassical properties of light.
We have measured the intensity correlation of pulsed squeezed light generated by a degenerate optical parametric amplifier seeding weak coherent input signal. When the signal was deamplified, the correlation showed antibunching and the probability distribution of the photon number was sub-Poissonian, both of these being nonclassical properties of light.
APPLIED PHYSICS B-PHOTOPHYSICS AND LASER CHEMISTRY 55(3) 233-241 1992年9月
Broadband high level squeezing was clearly observed from 100 kHz to 80 MHz using crystals Ba2NaNb5O15 of 5 mm length, MgO: LiNbO3 Of 19 mm length and KNbO3 of 5.8 mm length. Maximum noise reductions detected on a spectrum analyzer were -1.2 dB (-24%), -1.25 dB (-25%), and -1.8 dB (-34%) for the three crystals, respectively. The maximum squeezing is limited mostly by "optical index damage" of the parametric crystals. A detailed analysis of the beam parameters traced along the pump beam, squeezed vacuum, etc. is given. A detailed discussion on the evaluation of the initial squeezed level is given. A preliminary experiment with compressed laser pulses to avoid the optical damage is also described.
APPLIED PHYSICS B-PHOTOPHYSICS AND LASER CHEMISTRY 55(3) 233-241 1992年9月
Broadband high level squeezing was clearly observed from 100 kHz to 80 MHz using crystals Ba2NaNb5O15 of 5 mm length, MgO: LiNbO3 Of 19 mm length and KNbO3 of 5.8 mm length. Maximum noise reductions detected on a spectrum analyzer were -1.2 dB (-24%), -1.25 dB (-25%), and -1.8 dB (-34%) for the three crystals, respectively. The maximum squeezing is limited mostly by "optical index damage" of the parametric crystals. A detailed analysis of the beam parameters traced along the pump beam, squeezed vacuum, etc. is given. A detailed discussion on the evaluation of the initial squeezed level is given. A preliminary experiment with compressed laser pulses to avoid the optical damage is also described.