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Sub-Poissonian pulses of light are generated by means of traveling-wave optical parametric deamplification.Upon direct detection the quantum noise on the deamplified pulses is measured to be below the shot-noise limit by as much as 0.5~0.2 dB (11~4 %). The parametric-gain dependence of the measured Fano factor -directdetection noise as a fraction of the shot-noise limit -agrees with the quantum theory of the amplifier when diffraction effects are taken into account.PACS number(s): 42.50.Dv, 42.50.Lc, 42.65.Ky A nondegenerate optical parametric amplifier (NOPA) is equivalent to two independent degenerate optical parametric amplifiers (DOPA's). Using this property and with a proper choice for the NOPA input state, one can produce squeezed vacuum at the output of one DOPA and a spatiotemporally matched local oscillator (LO) at the output of the other. Employing such a matched LO for detecting the squeezing generated by the first DOPA we have measured up to 5.8 dB of quadrature squeezing -the highest ever observed in a traveling-wave experiment [1].In this Rapid Communication we report that the above equivalence can also be utilized to generate sub-Poissonian (amplitude squeezed) light. The NOPA input state can be chosen in such a way that when the output of one DOPA is maximally amplified, which occurs for a given pump-phase setting, that of the other is maximally deamplified. If the amplified output is directly detected and used to lock the pump phase, then the output of the deamplified DOPA locks into an amplitude squeezed state. Upon direct detection the noise on the deamplified DOPA output falls below the shot-noise limit. In our experiment the minimum measured Fano factor of 0. 89+. 0.04 ( -0.5 0.2 dB) is in agreement with the prediction of the quantum theory of a DOPA when the effects of gain-induced diffraction are taken into account.Generation of sub-Poissonian light has a long history. The landmark experiment of Short and Mandel [2] that demonstrated the sub-Poissonian nature of resonance fluorescence was followed by many reports of the generation subPoissonian light from a variety of physical systems [3 -6]. The most successful system to date has been the constantcurrent driven semiconductor laser [5]. However, to obtain good squeezing the laser had to be cryogenically cooled and closely coupled to the photodetectors. The use of roomtemperature, commercial lasers results in degradation of observed squeezing due to feedback and mode competition effects [6]. In contrast, a traveling-wave device, such as a parametric amplifier, is expected to be free from the above degrading effects. This Rapid Communication reports the generation of sub-Poissonian light by means of travelingwave parametric amplification. An earlier paper reported the observation of photon antibunching, a related nonclassical effect, in parametric amplification [7]. *FAX: (708)491-4455.1050-2947/95/51(5)/3429(4)/$06. 00 F = 1 -r/+ rg/g where g =(~p~+Iv~) is the maximal gain experienced by the amplified output of DOPA2, and 0~y~1 is the ove...

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