High sensitivity and resolution integrated optical system for portable Raman spectrometer.

An integrated optical system with high sensitivity and resolution was presented. This was made possible by coupling a probe to a monochromator directly, using an aspheric lens and an achromatic lens in the coupling path, using a dichroic filter with high transmission and a steep transitional zone as a beam splitter, increasing the throughput of the monochromator, and optimizing its structural parameters. This optical system has a high sensitivity; the tested spectrogram of a glass rod demonstrated that the signal-to-noise ratio measured by the integrated optical system was almost 4 times as high as an independent probe and monochromator. The optical system also has the advantages of high resolution (4  cm^-1 or 0.28 nm), low cost, and portable size. This work lays a good groundwork for the development of a high sensitivity, high resolution, and low cost integrated portable Raman spectrometer.