Interference on thin-film and metamaterial absorbers enables coherent control and processing of quantum light. Recently, this phenomenon was used to demonstrate deterministic control of photon absorption probability, quantum states filtering, anti-Hong-Ou-Mandel interference, and application of geometric (Berry) phase for remote control of light dissipation. Here, we expand these ideas by introducing the regime of distributed coherent absorption where light quanta are absorbed within spatially separated active layers. We show that this scheme allows photon number discriminating detection free from the limitations of conventional temporal and spatial multiplication approaches. Free space and integrated designs are discussed.
Classical Hong-Ou-Mandel (HOM) effect – two-particle interference on a lossless beamsplitter, reveals the fundamental difference between bosonic and fermionic particles. As a result of such interference, pairs of bosons coalesce while pairs of fermions anti-coalesce. Here we report an observation of the anti-HOM effect where bosons anti-coalesce and fermions show coalescent-like behavior when interfere on a lossy beamsplitter. By exploiting two-photon entangled states, we provide an experimental demonstration of the anti-HOM effect for both bosonic and fermionic spatial wavefunctions of the photons. This fundamental phenomenon may enrich quantum information and metrology protocols where states of entangled photons are dynamically converted.
Dissipation was traditionally considered as a destructive effect for quantum phenomena such as quantum light interference. In spite of this, correctly designed dissipation may provide an additional degree of freedom for quantum light control. Here we investigate, both theoretically and experimentally, different aspects of coherent quantum light interaction with lossy beamsplitters. Applications of dissipative interference for quantum technology are discussed.
We report the experimental results of generation and coherent detection of narrow linewidth tunable terahertz radiation at room
temperature utilizing a difference frequency generation as a result of stimulated scattering in the nonlinear crystal of MgO:LiNbO3.
The terahertz radiation was generated from an all-solid-state tunable injection-seeded THz-wave parametric generator (is-TPG), which
emits the monochromatic THz-wave over a wide tunable frequency range from 0.6 THz to 2.4 THz with the linewidth of narrower
than 100 MHz. Mixing of terahertz radiation (frequency &ohgr;T ) with a near-infrared intense pump pulse (frequency &ohgr;P ) results in the
excitation and amplification of the difference frequency component with frequency &ohgr;i =&ohgr;P -&ohgr;T, which is detected with a InGaAsbased photodiode. We demonstrate this method a fast response and very sensitive THz-wave detection running at room temperature,
which is at least three of magnitude faster and two of magnitude more sensitive than a typical Liquid-He cooling Si bolometer for
detecting the quasi-cw THz-wave beam. This detection technique is possible for coherent detection, it can measure the THz electric
field, not only the intensity. As a result, the phase information is preserved, the real and imaginary parts of a sample's dielectric
function may be determined simultaneously with this detection.
We carried out real-time measurement of gas density using monochromatic terahertz waves. The THz-wave absorbance is useful to measure the density of a gas having a characteristic spectrum in the THz region. We used the ring cavity THz-wave parametric oscillator (ring-TPO) as a monochromatic tunable THz-wave source. One can change the oscillation frequency of ring-TPO with a rotating galvano mirror forming the ring cavity. The frequency can be changed by synchronization with a repeating pump-pulse of 500 Hz. We demonstrated real-time measurement of the gas density in R-22, which had some spectral structure in THz frequency region. The gas density in the sample cell was changed by controlling the pressure to lower than 1 atm. When the gas density in the cell was the most tenuous, the maximum sensitivity was about 5%, which was limited by the fluctuation of THz-wave intensity.
We have demonstrated a quasi-monolithic THz-wave parametric oscillator (TPO) to confer more stability, a lower
threshold, and more compact size on THz-wave generating devices. In this report, we describe narrow linewidth
generation in a quasi-monolithic TPO. The cavity configuration was designed so that the noncollinear phase-matching
condition was satisfied in the crystal. A 5 mol% MgO:LiNbO3 crystal within dimensions of 15 mm × 20 mm with three
surfaces for total reflection was used as a nonlinear optical crystal. The quasi-monolithic TPO in a ring-cavity
configuration consisted of a nonlinear optical crystal and a super-mirror that reflected the idler beam (&lgr; > ca. 1067 nm)
and transmitted the pump beam (1064 nm). We obtained narrow oscillation linewidth of < 760 MHz at 1.6 THz of THz-wave
radiation. The low threshold of the oscillation was around 5.4 mJ/pulse.
We developed a fast data-acquisition rate terahertz (THz)–wave spectrometer based on an all-solid-state achromatically injection-seeded THz-wave parametric generator (is-TPG). It takes only seconds to smoothly sweep the frequency range from 0.9 THz to 2.4 THz. This system has been used successfully in THz-wave absorption spectrum measurement with high brightness, a fast data-acquisition rate, and ease of handling.
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