Open-Path Ghost Spectroscopy Based on Hadamard Modulation

In order to achieve spectral detection in free space, an open-path ghost spectroscopy (GS) based on complementary Hadamard modulation is proposed. In the proposed system, a programmable spectral filter is used to modulate a series of Hadamard patterns to a broadband signal provided by an amplified spontaneous emission (ASE) source, and the spectrum-under-test is recovered by cross correlation between the power measured by an optical power meter and the Hadamard patterns. Both the simulation and experiment are carried out, and the highest spectral resolution up to 0.126 nm is achieved. Furthermore, the detection performance of the GS in a designed strong turbulence path is also demonstrated, which shows that the proposed GS is a promising solution to recover the optical spectrum in the condition of weak light and strong turbulence in the open path.