A modulator for modulating an incident beam of light, the modulator comprising a plurality of equally spaced-apart elements, each of which includes a light-reflective planar surface. The elements are arranged parallel to each other with their light-reflective surfaces parallel to each other. The modulator includes means for supporting the elements in relation to one another and means for moving particular ones of the elements relative to others so that the moved elements transit between a first configuration wherein the modulator acts to reflect the incident beam of light as a plane mirror, and a second configuration wherein the modulator diffracts the light reflected therefrom. In operation the light-reflective surfaces of the elements remain parallel to each other in both the first and second configurations. The perpendicular spacing between the reflective surfaces of the respective elements is equal to m/4 × the wavelength of the incident beam of light, wherein m equals an even whole number or zero when the elements are in the first configuration and m equals an odd whole number when the elements are in the second configuration.

Method and apparatus for modulating a light beam

Holography, coherent light amplification and optical phase conjugation with photorefractive materials

Wave front shaping, the ability to manipulate light fields both spatially and temporally, in complex media is an emerging field with many applications. This review summarizes how insights from mesoscopic scattering theory have direct relevance for optical wave control experiments and vice versa. The results are expected to have an impact on a number of fields ranging from biomedical imaging to nanophotonics, quantum information, and communication technology.

Light fields in complex media: Mesoscopic scattering meets wave control

Nonlinear optical mixing can be used to perform a variety of new optical functions, as well as real-time holography. The theory and some of the first experiments are described.

Phase conjugate optics and real-time holography

It is proposed that the process of nonlinear optical phase conjugation can be utilized to compensate for channel dispersion and hence to correct for temporal pulse broadening. Specifically, a four-wave nonlinear interaction is shown to achieve pulse renarrowing. Spectral bandwidth constraints of the input pulse are presented for typical phase-conjugate interaction parameters.

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Compensation for channel dispersion by nonlinear optical phase conjugation.

Conjugate wave-front generation and image reconstruction by four-wave mixing (A)

This Letter is the first report of the observation of amplified reflection and self-oscillation produced by degenerate optical four-wave mixing by using a resonantly enhanced Kerr nonlinearity in atomic sodium vapor. Phase-conjugated reflected waves with intensities 100 times greater than input-signal intensities were achieved with only 40-kW/cm2 pump intensity.

Observation of amplified reflection by degenerate four-wave mixing in atomic sodium vapor.

This is the first reported demonstration of cw wavefront conjugation by degenerate four-wave mixing in a solid. Conversion efficiencies of 3% for conjugate-wave generation were obtained in a ruby crystal using a cw argon-ion laser.

Continuous-wave backward-wave generation by degenerate four-wave mixing in ruby

A laser utilizing F2+ centers in KF and yielding pulses 3–5 psec wide continuously tunable over the 1.24–1.45-μm range is described. The mode locking was achieved through synchronous pumping with ~100-psec-wide pulses at 1.064 μm. Operated cw, the laser yielded greater than 2.3 W near band center and greater than 1 W over most of the tuning band for ~5-W input. At any given wavelength, time-average mode-locked output power was at least half the corresponding cw value.

Color-center laser generates picosecond pulses and several watts cw over the 1.24 - 1.45-Mu m range.

The invention relates to a variable attenuator having two phase gratings (1 and 2) with rectangular grooves. In a first embodiment of the present invention the gratings are slidably mounted (10, 20, 30) so that the gratings have the grooves parallel and the faces in close proximity. As one grating is translated relative to the other the light passing through the device may be varied from total extinction to substantially total transmittance. A single device can be fabricated to provide this attenuation for radiation spanning the visible spectrum. In other embodiments the gratings are fixed relative to one another and the entire device is moved relative to the beam to be attenuated.

David M. Bloom

Papers

Conjugate wave-front generation and image reconstruction by four-wave mixing (A)

Observation of amplified reflection by degenerate four-wave mixing in atomic sodium vapor.

Continuous-wave backward-wave generation by degenerate four-wave mixing in ruby

Color-center laser generates picosecond pulses and several watts cw over the 1.24 - 1.45-Mu m range.

Variable attenuator for laser radiation