David Edward Watkins

Phase locking two beams by means of seeded Brillouin scattering

We have demonstrated that the phases of the stimulated Brillouin scattering reflections of two separately focused pump beams can be locked to a common phase by a backward seed of pump laser light.

Observation of amplified reflection through degenerate fourwave mixing at CO(2) laser wavelengths in germanium.

We report the first known observation of amplified reflection through degenerate four-wave mixing at 10.6 microm. Reflectivities of over 100% are reported in both n-type and p-type germanium at pump intensities of about 100 MW/cm(2). The maximum reflectivity reported is 800% in p-type Ge.

Observation of resonantly enhanced degenerate four-wave mixing in doped alkali halides

We describe the first reported observation of resonantly enhanced phase conjugation through degenerate four-wave mixing (DFWM) in doped alkali halides. We also describe the first reported quantitative comparison of the resonant DFWM process in the infrared with the theory of Abrams and Lind [Opt. Lett. 2, 94 (1978); 3, 205 (1978)]. The comparison for small values of alpha0L is shown to be excellent. For alpha0L in excess of 3, experiment and theory diverge because of pump attenuation by the resonant medium.

Determination of the third-order nonlinear optical coefficients of germanium through ellipse rotation

We describe the first reported direct determination of the 10 -Am nonlinear susceptibility in intrinsic Ge through time-resolved ellipse rotation. We found that X(3)(1111). = 2.5 X 10(-11) esu and X(3)(1221)= 1.3 X 10(-11) esu, significantly below previous estimates.

Effect of signal frequency on four-wave mixing through stimulated Brillouin scattering

We present measurements of the dependence of the phase-conjugate reflectivity on signal frequency for Brillouinenhanced four-wave mixing at pump intensities above the threshold instability. The measurements were made in TiC1(4) at lambda = 1 microm and are consistent with a computer model of the reflectivity. We have observed that the frequency of the conjugate beam is independent of the frequency of the input signal beam in the unstable regime.

Application Of Pulse Compression And Shaping To The FEL Photoelectric Injector

We discuss the application of self-phase modulation and grating pulse compression to the generation of temporally trapezoidal optical pulses for controlling the electron beam emittance and energy spread in an FEL photoelectric injector. Pulse compression in a single-stage pulse compressor, with background reduction based on the nonlinear birefringence of the optical fiber, yields 3-ps, compressed pulses without background pedestals or sidelobes. Trapezoidal, flat-topped pulses with 20-ps FWHM and 4-ps risetime have been obtained through self-phase modulation and group-velocity dispersion of the 3-ps pulses in a second fiber. Pulse shaping through Fourier transform amplitude and phase masking in the frequency domain and the amplification of the trapezoidal pulses are also discussed.

Generation and amplification of temporally 'square' optical pulses for the FEL photoelectric injector

The authors discuss the application of self-phase modulation and grating pulse compression to the generation of optical pulses suitable for controlling the electron beam emittance and energy spread in a FEL (free-electron laser) photoelectron injector. Pulse compression in a single-stage pulse compressor, with background reduction based on the nonlinear birefringence of the optical fiber, yields 5-10-ps Gaussian pulses. Temporarily square pulses with 15-ps FWHM (full width at half maximum) and 5-ps risetime have been obtained through self-phase modulation and group-velocity dispersion of the 5-ps pulses in a second fiber. Pulse shaping through the use of nonlinear birefringence in optical fibers is also discussed.<<ETX>>

New Developments in Optical Phase Conjugation

Optical phase conjugation has ceased to be regarded as merely a scientifically interesting laboratory phenomenon. It is now being invoked as a tool to deal with various laser problems that do not yield easily to more conventional solutions. Thus, in addition to the continuing research on the fundamental mechanisms in various methods of phase conjugation, activities at the Los Alamos National Laboratory have also addressed development issues of more practical relevance. For a tutorial introduction to the concepts of optical phase conjugation we direct the reader to references [1] and [2], whereas more details on various subtopics can also be found in [2].