Fig. 1. Schematic diagram of the interaction between light and turbid medium

Fig. 2. Transmitted and reflected light intensity varies with sample thickness

Fig. 3. Sample detection using quartz tube enhanced Raman fiber probe

Fig. 4. Transmittance curves of quartz glass

Fig. 5. Structure of tapered quartz tube

Fig. 6. Metal-coated hollow core fiber

Fig. 7. Comparison diagram of spectral backgrounds of different fibers

Fig. 8. Quartz tube enhanced fiber Raman probe. (a) Schematic diagram of probe design; (b) Schematic diagram of probe section; (c) Physical of Raman probe

Fig. 9. Raman spectroscopy experiment setup. (a) Schematic diagram; (b) Physical diagram

Fig. 10. Powder detection with different probes. (a) Schematic diagram; (b) Experimental results

Fig. 11. Experimental setup and results of powder samples detection at different depths. (a) Experimental setup; (b) Probe-to-bottom=0.5 cm; (c) Probe-to-bottom=3.5 cm; (d) Probe-to-bottom=6.5 cm