We report degenerate four-wave mixing (DFWM) of visible radiation in borosilicate glasses doped with crystallites of the mixed semiconductor CdSxSe1−x. These semiconductor-doped glasses—available commercially in the form of colored glass filters—exhibit third-order nonlinearities of ~10−9–10−8 esu for DFWM with short (~10-nsec) laser pulses at various visible wavelengths. Our studies on the temporal decay of the transient gratings indicate that the nonlinearity is not thermal in origin but may be attributed to the generation of a short-lived electron–hole plasma. In contrast with DFWM experiments in other semiconductors invoking gratings of optically generated carriers (or other mobile particles), we report unique diffusion-independent decay of the gratings in these glasses; this is deduced from the dependence of the intensity and polarization of the DFWM signal on the polarization combinations of the input beams. Finally, we report detailed data on the aberration-correction properties of these isotropic glasses.

Degenerate four-wave mixing in semiconductor-doped glasses

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

Phase conjugate optics and real time holography (A)

Active optical systems are those in which real-time control over optical wavefronts is employed to optimize system perference in the presence of random distrurbances. Applications include 1) outgoingwave systems for maximizing the power density of a laser beam on a target and 2) received-wave systems for maximizing the angular resolving power of a telescope viewing a distant object through a turbulent atmosphere. In this tutorial-review paper, the basic concepts of active optics systems and their historical evolution are discussed, from early figurecontrol systems with a servo bandwidth of less than 1 Hz to the recently developed high-bandwidth systems for atmospheric compensation with bandwidths of several hundred hertz. A critical comparison of the various approaches to wavefront sensing is then made covering both coherent (laser) and incoherent (white-light)systems. Current techniques for wavefront correction including Bragg cells, segmented mirrors, thin-plate deformable mirrors, monolithic mirrms, and membrane mirrors are described. The performance analysis and optimization of closed loop systems is covered using two basic models. The paper concludes with a review of the design and performance of five current experimental active optical systems, with some comments on future applications.

Active optics: A new technology for the control of light

The real-time information processing and manipulation of electromagnetic waves using nonlinear Qptical techniques has resulted in a myriad of new applications in diverse fields such as quantum electronics, image processing, optical computing, adaptive optics, and nonlinear spectroscopy. In this paper, we review and explore the field, provide a historical perspective, analyze several of the nonlinear interactions useful for the generation of phase-conjugate replicas, and conclude with a brief survey of potential applications and suitable nonlinear media.

Nonlinear Optical Phase Conjugation

We have obtained quantitative measurements on the correction of severely aberrated laser beams using stimulated Brillouin scattering (SBS) at 0.69 μm. We have shown that under certain conditions SBS can be used to restore an aberrated optical beam to its original unaberrated condition. When an optical beam double passes an aberrating region after reflecting from an “ordinary” mirror (i.e., a plane mirror) the aberration is twice that obtained from a single pass. However, when the aberrated beam enters a medium that allows SBS to occur, it emerges from its second pass through the aberrating medium in the same condition as that in which it originally entered. Quantitative experiments are described in which a single-mode ruby laser beam is intentionally aberrated by passing it through an etched plate. When the beam is allowed to double-pass the plate using an ordinary reflector (i.e., plane mirror), the beam divergence is more than 10 times the diffraction-limited divergence. However, when we replace the ordinary reflector with a cell in which SBS can take place, the SBS reflected beam is restored to diffraction-limited divergence when it is allowed to pass back through the aberrating medium. Applications of this time-reversal or phase-reversal technique for correcting aberrations in optical trains and atmospheric turbulence are discussed.

Correction of phase aberrations via stimulated Brillouin scattering

This paper deals with certain nonlinear effects that can directly generate a wavefront which is the phase conjugate of the incident field. These phenomena can be exploited in pulsed laser systems to remove aberrations in the optical train as well as ab-errations arising from turbulence in the atmosphere. We discuss our measurements of the effectiveness of this conjugation process using a ruby laser and stimulated Brillouin scattering in a CS2 waveguide device. Measurements are made of the divergence angle of the beam after correction. The application of conjugate processes realizable in SBS, SRS, parametric downconversion, and four-wave mixing is considered for typical CO2 laser systems. System gain, backscatter limitations and parasitic oscillation are discussed for typical pulsed amplifier systems. Amplified spontaneous emission and unwanted glint returns from optical defects appear to be the most serious limitations.

Nonlinear Optical Phase Conjugation for Laser Systems

This paper deals with certain nonlinear effects that,can directly generate a wavefront which is the phase conjugate of the incident field. These phenomena can be exploited in pulsed laser systems to remove aberrations in the optical train as well as aberrations arising from turbulence in the atmosphere. We discuss our measurements of the effectiveness of this conjugation process using a ruby laser and stimulated Brillouin scattering in a CS2 waveguide device. Measurements are made of the divergence angle of the beam after correction as a function of interaction length. The application of conjugate processes realizable in SBS, SRS, parametric down conversion, and four-wave mixing is considered for typical CO2 laser systems. System gain, backscatter limitations and parasitic oscillation are discussed for typical pulsed amplifier systems. Amplified spontaneous emission and unwanted glint returns from optical defects appear to be the most serious limitations.

Victor Wang

Papers

Correction of phase aberrations via stimulated Brillouin scattering

Nonlinear Optical Phase Conjugation for Laser Systems

Nonlinear Optical Phase Conjugation For Laser Systems