Modulation and lock-in amplifier free coherent Raman spectroscopy

Label-free spectroscopy and imaging are valuable tools that permit the study of biological samples without the need for exogenous labels, allowing for investigation of unperturbed biological systems. Here, we introduce a novel form of impulsive Raman detection that eliminates the need for modulation of the pump pulse and lock-in detection. We demonstrate and characterize this novel detection technique and benchmark it against conventional lock-in based detection. By eliminating the largest source of dispersion in the experimental system, the overall complexity of impulsive Raman is significantly reduced and allows more flexibility in using high NA objectives for biological spectroscopy and microscopy.