Observation of an Optical Difference Frequency

Jan Peřina

Naohiro Tanno, Kenichi Yokoto, Humio Inaba

Low-loss, coherent two-photon propagation and pulse breakup with peak amplification are observed resulting from two-photon resonant self-induced transparency of different-frequency optical pulses interacting with a three-level system in potassium vapor. Theoretical analysis yielding new area equations for two different-frequency pulses with computer solutions agrees well with the observed results.

Toshiki Kobayashi, Rikizo Ikuta, Shinro Yasui +9 more

Recently a single-photon frequency converter by a nonlinear optical medium with a strong pump light [1] has been actively studied for quantum information processing [2]. The effective Hamiltonian of the process is described as a frequency-domain beamsplitter, which has two different frequency modes in its input and output. The transmittance is tunable by a pump power for the nonlinear optical effect. Such a frequency-domain beamsplitter is expected to cause an interference of two photons of different colors [3] in the context of a Hong–Ou–Mandel (HOM) experiment. In this study, we first observed the HOM dip in an optical range by using a frequency-domain beamsplitter.

Jan Peřina

Jietai Jing, Sheng Feng, Russell Bloomer +1 more

We observed continuous-variable entanglement between the bright beams emitted above threshold by an ultrastable optical parametric oscillator (OPO), classically phase locked at a frequency difference of $161.827\phantom{\rule{0.2em}{0ex}}324\phantom{\rule{0.2em}{0ex}}0(5)\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$. The amplitude-difference squeezing is $\ensuremath{-}3\phantom{\rule{0.3em}{0ex}}\mathrm{dB}$ and the phase-sum one is $\ensuremath{-}1.35\phantom{\rule{0.3em}{0ex}}\mathrm{dB}$. Besides proving entanglement in a phase-locked OPO, such outstanding frequency-difference stability paves the way for transferring entanglement between different optical frequencies and densely implementing continuous-variable quantum information in the frequency domain.