A new type of optical waveguide utilizing an antiresonant reflector is described. Implementation in the SiO2-Si system gave losses as low as 0.4 dB/cm for the TE mode. The TM mode loss is >60 dB/cm, making the device an excellent planar technology integrated optic polarizer.

A simple technique is described for gating light on and off on the picosecond time scale. The gate is built in much the same fashion as traditional Kerr cells, the difference lying in the use of powerful optical pulses rather than electrical pulses to induce a birefringence in various liquids. The direct observation of the exponential decay (τ = 32 ± 6 psec) of the birefringence induced in nitrobenzene shows that orientational effects are largely responsible for the refractive index changes induced by light in this liquid.

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The ejection of electrons from inner shells of atoms through photoionization is suggested as a straightforward means of creating population inversions at vacuum uv and x-ray wavelengths. This can be accomplished by photon sources covering broad bands. Sodium vapor and solid copper are examined as possible candidates for laser action at 372 Å and 1.54 Å, respectively. A first-rise traveling wave pump must be used; pumping powers required for superradiant operation run into several gigawatts, with rise times ranging from 10−9 sec in the near-vacuum uv to 10−15 sec in the x-ray region.

Three new results have been obtained with a recently developed camera of 10-psec framing time: (1) The effect of the finite speed of light in photographing relativistic objects is experimentally demonstrated, by photographing a dumbbell-like entity formed by two packets of light. In contrast to material objects, which, theory predicts, should appear rotated, the light dumbbell appears sheared. (2) Photographs of the mode-locked Nd: glass laser radiation show numerous subsidiary pulses accompanying the main ultrashort pulses in the train. The latter have durations ranging from 7 psec to 15 psec. (3) The technique of gated picture ranging, previously used with nanosecond pulses, is extended to the picosecond range where a resolution of 1 cm is demonstrated. Some potentially useful applications are proposed.