The proposed device, developed by our researchers, employs a multimode blue laser diode which receives feedback from a concentric bidirectional multi-pass cavity. The laser bandwidth is reduced to 4 cm-1 as a result of the feedback provided via a volume Bragg grating. As a result, the spectra of spontaneous Raman scattering from ambient atmospheric air is recorded within a limit of detection below 1 parts-per-million. The effectiveness of the device is demonstrated through detection of acetone, methane and isotopic carbon dioxide in breath. This technology can be used in medical diagnostics, hazardous gas monitoring, environmental detection or even in simple home gas detection/monitoring.
Experimental Setup Demonstrating How the Spontaneous Raman Emission is Collected Collinearly