The Current StudyThe experimental method focuses on generating second harmonic light with precisely controlled spatial coherence. Through this approach, the researchers can effectively design and manipulate the coherence of the fundamental beam, thereby shaping the coherence characteristics of the second harmonic light with a high degree of control. The data clearly show that the spatial coherence of the fundamental speckle fields directly shapes the coherence of the second harmonic output. In particular, the second harmonic coherence patterns closely reflect the engineered coherence of the input, confirming that spatial coherence can be purposefully designed and preserved through frequency conversion. ConclusionThis study offers compelling experimental evidence that high spatial coherence, long considered a prerequisite in nonlinear optics, is not strictly necessary.