Coherent optical pulse reshaping in a resonant molecular absorber

The coherent reshaping of short‐duration (2–40 nsec) N₂O laser pulses in a resonant NH₃ absorber is studied for a variable number of absorption lengths (αl ≤ 14). For small‐area square pulses, the reshaping can produce subnanosecond pulses at the leading and trailing edges. A rapid phase reversal gives rise to amplification for times comparable to the transverse relaxation time. Zero‐degree pulses ${\mathrm{[\int }}_{\mathrm{-\infty }}^{\infty }\mathcal{E}\text{(z,t)\hspace{0.17em}d\hspace{0.17em}t=0]}$ are observed to propagate with enhanced transmission for both short‐duration low‐intensity pulses and longer pulses of intensity sufficient to enable observation of optical nutation effects.