An apparatus (1) and associated method for spectroscopic analysis of a sample (30). The appartaus comprising: a first light source (12) configured to illuminate a sample comprising a structure with first light (13) configured to scatter at one or more interfaces (34) of the structure (32)；a second light source (14) configured to illuminate the sample with second light (15) configured to excite one or more molecules in the structure (32) to thereby cause thermal expansion of the structure (32)；a controller (10) configured to control the second light source (14) to: modulate the second light (15) to thereby modulate thermal expansion of the structure (32), and vary a wavelength of the second (15) light across a wavelength interval； anda detector (16) configured to receive first light (13) scattered at the one or more interfaces (34) of the structure (32) during different phases of the modulation of the second light (15) for spectroscopic analysis.
