Abstract

Photon-photon scattering in a vacuum^1a is perhaps one of the most fundamental mechanisms giving rise to nonlinear optical effects.^1b However, none of the previously proposed effects has been observed in the experiment.^1b Recently, we have demonstrated the feasibility of new nonlinear magneto-optical effects in a vacuum that gives rise to optical second-harmonic generation (SHG) under the action of both strong dc magnetic field (Ho) and high intensity optical laser radiation available.² Here we review practical aspects of possible experiment on the SHG in vacuum. Stipulating that signal-to-noise ratio is sufficiently high, e.g., =10², and using pulsed magnetic field H₀ ~ 8 × 10⁶ Gauss, one can obtain the least laser intensity of I₁ ≃ 10¹⁴W/cm². With such an intensity or even higher, the average number of detected photons per pulse nears unity. One can use averaging of photon counts over a few laser beam lines for a single pulse or/and over many pulses of laser. NOVA with λ₁ ~ 0.35m or GEKKO XII with λ ~ 0.53 μm can provide the laser energy of 6-10 kJ/pulse in each of 10~12 beam lines. If all the beam lines are used, the probability of not observing any SHG photons can be as low as ~10^-6-10^-4. Using picosecond lasers, the number of pulses required to observe the effect is ~10⁶-10⁷. SHG from the plasma of the ionized residual gas becomes negligible compared with vacuum contribution when the vacuum pressure is < 10^-5 torr.

© 1990 Optical Society of America