C. R. Giuliano

Coherent coupling of laser gain media using phase conjugation

We have experimentally demonstrated a laser energy-scaling technique, based on a phase-conjugate oscillator/amplifier scheme that permits the coupling of several parallel amplifiers to form a single coherent output beam. This, is achieved despite dramatic differences in the individual amplifier energies and optical path lengths. When many amplifiers are coupled together, energy can be scaled significantly beyond the limit imposed by the maximum available volume of a single active medium. Although the present demonstration utilized Nd:YAG, this technique is quite general and can be applied to a variety of laser media.

Polarization‐rotation and thermal‐motion studies via resonant degenerate four‐wave mixing

We report experimental observation of polarization rotation in resonant degenerate four‐wave mixing (DFWM) arising from the third‐order coupling of the electric fields. This effect allows investigation of molecular motion and its effect on the efficiency of the DFWM. By controlling the pulse width and therefore γ=T0/τp (where T0≡λ/vth) we show quantitative agreement with a third‐order density matrix perturbation calculation. In particular, using a CO2 laser at 10.6 μm and SF6 as the nonlinear medium, we show that for γ≫1 (stationary limit) we see no molecular motion and for γ≈1, we see a significant ’’washout’’ of one third–order polarization.

Enhancement of self-focusing threshold in sapphire with elliptical beams

The power threshold for optically induced bulk damage in sapphire is a sensitive function of the ellipticity of the incident beam shape. Experimental results are consistent with a simple self‐focusing theory.

Phase conjugation at 10.6 μm by resonantly enhanced degenerate four‐wave mixing

A resonantly enhanced phase‐conjugate 10.6‐μm signal has been generated in the saturable absorber SF6. Direct evidence of aberration correction is shown through the use of far‐field photographs taken with a pyroelectric vidicon camera. Reflection coefficients of 7% have been achieved in a few Torr of SF6 for a 2‐cm interaction length.

Laser‐induced damage in transparent dielectrics: ion beam polishing as a means of increasing surface damage thresholds

Polishing of sapphire surfaces with energetic Ar+ ion beams is shown to result in a substantial increase in laser damage threshold over that for conventionally polished surfaces. Data for both entrance and exit damage are presented. The results are interpreted in terms of an increase in surface strength with ion beam polishing.

Phase conjugate master oscillator‐power amplifier using BaTiO3 and AlGaAs semiconductor diode lasers

A double pass phase conjugate master oscillator‐power amplifier has been demonstrated at 820 nm using AlGaAs gain elements and BaTiO3 in a self‐pumped ring configuration. Single frequency operation with diffraction‐limited output beam quality was achieved at output powers in excess of 50 mW cw.

NONLINEAR ABSORPTION OF LIGHT. POSITIVE AND NEGATIVE SATURATION EFFECTS IN THE SAME ABSORBER

The optical transmission of platinum dithizonate dissolved in CCl4 was measured as a function of intensity at 6943 A. When a 35‐nsec pulse is used for excitation the transmission increases from its low‐level value at a power density of 0.1 MW/cm2, goes through a maximum at 10 MW/cm2 and then decreases to its low‐level value at 80 MW/cm2. This material functions effectively as a passive Q switch for ruby and may provide power stabilization as well. A long‐lived cumulative bleaching effect is produced when the output from a non‐Q‐spoiled laser is used for excitation. The transmission behavior of this system at all intensities is discussed in terms of a generalized kinetic mechanism.

On the equality of stimulated Brillouin scattering reflectivity to conjugate reflectivity of a weak probe beam

If a strong pump wave, with energy that is above threshold for stimulated Brillouin scattering, and a weak probe wave are incident into a nonlinear medium, then it has been shown by others that the reflectivity of the weak probe is equal to the reflectivity of the strong pump and that the probe is phase conjugated provided that the pump is phase conjugated. We present an analysis that predicts an exact equality of the reflectivities and identifies the parametric limitations.

Coupled cw dye lasers using intracavity four-wave mixing.

An experimental investigation of laser-oscillator frequency locking by a four-wave interaction was conducted. An experiment was performed that successfully demonstrated the locking of two cw dye lasers using this concept with Na vapor serving as the nonlinear (coupling) medium.

Coherent coupling of CW laser oscillators using intracavity four-wave mixing

A theoretical study of frequency locking laser oscillators using an intracavity four-wave interaction is discussed. An experimental demonstration that successfully locked two CW dye lasers using this concept was performed, along with intracavity four-wave mixing studies, with sodium vapor serving as the nonlinear (mixing) element. >