Shamrock sr 750

In spectral measurements, at location C in Fig. 2a the scattered light from one section of the collimated double jet beams (or the sideways emission) is coupled into a Shamrock spectrometer (Shamrock SR-750, Andor) equipped with an ICCD detector (DH740i-18U-03, iStar, Andor). In this case, in addition to the imaging lens, a couple of steering mirrors (not shown in Fig. 2a) are employed for rotating the sampled source section by 90-degree so that the image becomes parallel to the entrance slit of the spectrometer and so improved light coupling efficiency is achieved. Spectral measurements at the other three locations labeled by A, B and D respectively are made with a miniature fiber-pigtailed spectrometer (Model S2000, Ocean Optics) of lower sensitivity but more convenience of operation. In measuring the spectrum of the collimated jet beams (not the scattered light) at location D, three optical wedges are utilized to reflect off the beam three times and thus significantly reduce the optical power entering the spectrometer. It should be noted that for all the spectral traces given in this paper the spectral response of the detection system has not been corrected, and thus the relative heights of the spectral peaks, especially those in Fig. 1d, trace D in Fig. 2b do not present the real signal strength.