We discuss nonclassical light properties, in particular, focused on multi-photon quantum correlations in quantum optics. We analyze two-mode fields from a nondegenerate optical parametric oscillator below threshold using criteria introduced by Agarwal1 and Lee. Additionally, we identify that system parameters like pump and seed coherent amplitudes influence the nonclassicality of the output quantum state.
We propose a novel quantum interferometer based on two stimulated Parametric Down-Conversion (PDC) crystals seeded by weak coherent idler fields to investigate the relationship between the nonclassicality of the signal photon state and the fidelity of the conjugate idler photon state. We show that the purity of the signal photon state is tightly bounded by the entanglement between the signal photon and its conjugate idler photon, i.e., the fidelity of the idler state in the bipartite system, resulting in a novel complementarity relation for wave-particle duality. Moreover, we find that the nonclassical measure of the signal photon state is identical to the fidelity of the conjugate idler photon states prepared in each crystal. In our novel interferometer, the input beam splitter of the conventional SU(2) interferometer is replaced with two seeded SU(1,1) PDC systems that emit only a single photon at once from two crystals, thus producing an entangled superposition state where the conjugate idler photon states act as path detectors with controllable fidelity. We demonstrate that the presented quantum interferometer consisting of two stimulated PDC crystals positioned in parallel is an ideal setup for investigating and quantitatively understanding the complementarity relation of wave-particle duality.
Photothermal treatment (PTT) using nanoparticles has gained attention as a promising alternative therapy for malignant tumors. One strategy for increasing the selectivity of PTT is the use of macrophages as a cellular vector for delivering nanoparticles. The aim of the present study is to examine the use of macrophages as a cellular vector for efficient PTT and determine the appropriate irradiation power and time of a near-infrared (NIR) laser using real-time phase-contrast imaging. Thermally induced injury and death of cancer cells were found to begin at 44°C to 45°C, which was achieved using the PTT effect with gold nanoshells (NS) and irradiation with a NIR laser at a power of 2 W for 5 min. The peritoneal macrophage efficiently functioned as a cellular vector for the NS, and the cancer cells surrounding the NS-loaded macrophages selectively lost their cellular viability after being irradiated with the NIR laser.
We present an ultrabroadband supercontinuum (SC) frequency comb generation covering the optical spectrum
more than 1.2 octave from 570 nm to 1350 nm with a near flat-top power spectrum by using a mode-locked Yb
fiber laser at 1030 nm as a master oscillator (MO). The repetition rate of the MO that has a spectral-width
of 28 nm is 152 MHz and is phase-locked to a reference frequency synthesizer. A power amplifier is used to
boost up the output power up to 1.3 W and the positively chirped amplified pulses are compressed by using
a transmission grating pair. We used a commercially-available 10-cm long photonic crystal fiber that has two
zero-dispersion wavelengths at 800 nm and 1093 nm, respectively, to generate an ultrabroadband SC frequency
comb. Optical spectrum depending on the frequency chirp and pulse-width of the amplified pulses are analyzed
to find an optimum coupling power as well as an optimum chirp parameter. We found that a dimensionless chirp
parameter of 8.6 and a pulse-width of 517 fs for a chirped Gaussian pulse resulted in the optimum spectrum
width of 1.2 octave.
A two-photon transition in cold Rb atoms will be probed with a phase-coherent wide-bandwidth femtosecond laser comb. Frequency domain analysis yields a high resolution picture where phase coherence among various transition pathways through different intermediate states produces interference effects on the resonantly-enhanced transition probability. This result is supported by the time domain Ramsey interference effect. The two-photon transition spectrum is analyzed in terms of the pulse repetition rate and carrier frequency offset, leading to a cold-atom-based frequency stabilization scheme for both degrees of freedom of the femtosecond laser.
We have established a portable I2-stabilized Nd:YAG laser for the purpose of making wavelength standards at 532 nm and 1064 nm. All the optical parts of the laser systems were arranged on a 45 cm X 45 cm breadboard. The system was transported from NRLM to JILA for frequency comparison. The results of the comparison show that the Allan Variance of the portable laser reached < 3 X 10-13 when the integration time (tau) is larger than 100 s. The frequency differences between the NRLM and JILA lasers during 3-day measurements were consistent within +/- 35 Hz, but the matrix-averaged standard deviation of about 310 Hz, and offset are regarded as not yet fully satisfactory. The stability of the portable laser was further improved to about 3 X 10-14 by using a longer iodine cell and several frequency stabilization techniques.
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