Ultra-High Dynamic Range Optical Modulators For Ladar Scene Projection

Laser Detection and Ranging (LADAR) scene simulators are an important tool for characterizing the LADAR systems used by missiles and aircraft. The scene simulator is used for incremental and final testing of the embedded hardware and software that enable real-time operation of the LADAR system. An important component in the scene simulators is a large 256x256 array of optical sources or pixels that deliver nanosecond wide optical pulses with the high dynamic range that is typical of real scenes. This dynamic range requirement is greater than 62 dB. This proposal addresses the design of an enhanced dynamic range modulated optical source based on a compact Mach-Zehnder (MZI) intensity modulator. The novel design will ensure that the dynamic range available is more than ten thousand times greater than what is obtainable from conventional MZI modulators. The MZI device will be capable of bandwidths in excess of 1 GHz, and can be integrated onto a larger optical chip containing 8, 16 or 32 such devices. The array of optical pixels in the scene generator must also provide 4096 levels of gray, equivalent to 12-bit linearity. This linearity requirement may be satisfied by pre-compensation distortion in the external driving electronics.