Search for sub-eV axion-like resonance states via stimulated quasi-parallel laser collisions with the parameterization including fully asymmetric collisional geometry

We have searched for axion-like resonance states by colliding optical photons in a focused laser field (creation beam) by adding another laser field (inducing beam) for stimulation of the resonance decays, where frequency-converted signal photons can be created as a result of stimulated photon-photon scattering via exchanges of axion-like resonances. A quasi-parallel collision system (QPS) in such a focused field allows access to the sub-eV mass range of resonance particles. In past searches in QPS, for simplicity, we interpreted the scattering rate based on an analytically calculable symmetric collision geometry in both incident angles and incident energies by partially implementing the asymmetric nature to meet the actual experimental conditions. In this paper, we present new search results based on a complete parameterization including fully asymmetric collisional geometries. In particular, we combined a linearly polarized creation laser and a circularly polarized inducing laser to match the new parameterization. A 0.10 mJ/31 fs Ti:sapphire laser pulse and a 0.20 mJ/9 ns Nd:YAG laser pulse were spatiotemporally synchronized by sharing a common optical axis and focused into the vacuum system. Under a condition in which atomic background processes were completely negligible, no significant scattering signal was observed at the vacuum pressure of 2.6 × 10−5 Pa, thereby providing upper bounds on the coupling-mass relation by assuming exchanges of scalar and pseudoscalar fields at a 95% confidence level in the sub-eV mass range.

Scheme features of radio pulse gating for radar measurements

The model of a radio pulse stroboscopic converter consisting of a mixer and a narrowband filter tuned to the difference frequency of the carrier signals is considered. We demonstrate that the measurement of the phase structure of the input signals can be made at low frequency by amplitude methods by changing the phase both in the channel of the gating radio pulses and in the low frequency channel. The radio-pulse gating scheme goes into a phase-sensitive mode when the system clock frequency is synchronized with the second harmonic of the difference frequency, however, in this case, a parasitic phase modulation occurs in the converted signal, which does not depend on the transformation coefficient of the spectrum and is determined only by the duty cycle of the input signal. To eliminate parasitic modulation, which distorts the envelope of the output signal of the converter in a phase-sensitive mode, it is proposed to use an auto-shift circuit with a falling “slow” sawtooth voltage when generating gating radio pulses.

Development of a Cheap Helicopter Assisted Landing System Method

This paper presents a relatively cheap helicopter assisted landing system concept. A frequency modulated continuous radar (FMCWR) is used to check an unprepared landing area for the presence of interfering objects. The spectrum processing of the converted signal is used to provide multi target resolution. The experimental research is done by using a 4.3 GHz FMCWR radar. The converted signal spectra are provided for mirror and rough surfaces, as well for multiple targets in a case of interfering object existence.

Experimental Proof of the Characteristics of Short-Range FM Radar Converted Signal Spectrum for a Smooth Surface

This paper presents a natural experiment of the spectral processing of 4.3 GHz Frequency Modulated Continuous Wave Radar (FMCWR) converted signal. The FMCWR antennas are fixed above a smooth reflective surface. The converted signal spectrum is theoretically calculated and compared with the experimental data.

Terahertz Signal Generation in 1-D Photonic Crystals

Theoretical and numerical results are presented to assure that a tunable, narrow-band, coherent THz radiation source can be based on parametric down-conversion in aphotonic crystal. Our proposal is based on down-conversion mixing and a local-field enhancement mechanism that is available by tuning each of the two driving laserfields either to band-edge or to a defect mode in the band gap. The frequency of the down-converted signal can be tuned by intersecting two non co-linear laser sources. The polarizations are degenerate at normal incidence and have sub-THz down-conversion maximum. For aspecific sample geometry we show that by changing the angle of incidence of one tunable laser to 30 degrees the THz frequency is about11.5 THz for p-polarization and 3.5THz for s-polarization, since the angle-dependent transmission spectrum is different for p- and spolarizations.The peak conversion efficiency for both polarizations is enhanced by over two orders of magnitude. Finally we also introduce some preliminary experimental results which agree with the numerical results we present here.