Optical pulse shaping method and system based on multi-frequency acoustic-optic deflection and retro-diffraction based multi-delay generation

A system for performing an optical pulse shaping method, the system comprising:

• a radio frequency (RF) signal programming device,
• an acoustic-optic device comprising at least one of an acoustic-optic modulator or an acoustic-optic deflector,
• an optical lens system,
• a grating, and
• a frequency-stabilized laser system monitor, wherein:
• in the RF signal programming device, a user writes the frequency, amplitude, and phase of each component of an RF signal, and programmed RF signals are then combined, amplified, and transmitted to drive the acoustic-optical device in forms of sine waves;
• the acoustic-optic device converts the RF signal into a sound wave signal with a corresponding frequency, intensity, and phase, and performs multi-angle diffraction on an incident pulsed laser, to achieve an objective of beam splitting;
• based on acoustic-optic deflection principle, deflection angles between the incident pulsed laser and deflected beams are proportional to the frequencies of the sound wave signal under small angle approximation, so as to be configured by programming the frequencies of the RF signals, the amplitudes and phases of each deflected sub-pulse beams are controlled by the amplitudes and phases of the sound wave decided by those of the RF signals at the corresponding frequencies;
• the optical lens system comprises a wide-angle collimation lens to collimate multi-angle sub-pulse beams from the acoustic-optical device into parallel beams by converting angular difference from acoustic-optical device output into transverse displacements, while ensuring weak focusing of each beams, so as to improve a response bandwidth of retro-diffraction at the grating interface;
• the grating is positioned near focal planes of weakly focused sub-pulse beams, the orientation of the grating is optimized to ensure retro-diffraction of a negative first order to optimally overlap with an incident direction, the transverse displacement of each sub-pulse beams leads to optical path length difference during the retro-diffraction, leading to relative optical delays among the retro-diffracted sub-pulses, wherein the relative optical delays are determined by a focal length of the optical lens system and the deflection angles of the acoustic-optic device, and are controlled by the frequency of the RF signal;
• each retro-diffracted sub-pulse passes through the wide-angle collimation lens and the acoustic-optical device again, wherein the grating diffraction occurs near a Gaussian optical waist of each beam, the retro-diffraction generates approximately time-reversed wavefront for each beam, which ensures that for each beam diffracted twice by the same sound wave ends up with output direction to be the reversed direction of the original incident pulse, with an overall diffraction efficiency insensitive to the sub-pulse delay, resulting in recombination of all the sub-pulse beams into an incident beam path, and along a reversed direction to be coupled into a single-mode optical device after an optical circulator as the output, any sub-pulse beams that do not follow such reversed path is blocked from entering the output;
• by controlling inter sub-pulse delays, amplitudes and phases of the sub-pulses, nearly arbitrary waveforms within an input pulse bandwidth and total delay are synthesized by the sub-pulse sequence, by programming the RF waveforms;
• and
• the frequency-stabilized laser system monitor is configured to detect the amplitudes and phases of the sub-pulse sequence in real time and to provide feedback for stabilizing a waveform from the output.