an all - optical nonlinear joint transform correlator has been implemented for the first time without using a spatial light modulator and digital processing in the fourier plane . the correlator utilizes energy transfer from two - beam coupling in the fourier plane . a compressional nonlinearity in the hard - clipped regime is implemented by pumping a weak plane wave with the intense joint spectrum of the reference and signal images . operation of this device rivals or exceeds that of the phase - only filter for detecting objects in cluttered noise . experimental results are compared with both plane wave and beam propagation simulations .