We demonstrate experimentally that a broad-area laserlike optical oscillator (a nondegenerate photorefractive oscillator) with structured injected signal displays two-phase patterns. The technique [de Valcarcel and Staliunas, Phys. Rev. Lett. 105, 054101 (2010)] consists in spatially modulating the injection, so that its phase alternates periodically between two opposite values, i.e., differing by pi.
Martinez, R., Esteban, A., Roldan, E., Staliunas, K., VALCARCEL, G., Silva, F. Experimental demonstration of phase bistability in a broad-area optical oscillator with injected signal. "Physical review A", 30 Novembre 2015, vol. 92, núm. 5, p. 1-4.