Due to the complexity of the fluid dynamics and non-linear reactions in the combustion zone, a simplified approach to study this process is required. Given these complexities, it is practically very challenging to take measurements in very high temperature and pressure zones in practical combustion systems, and if by any means those measurements can be made, it is equally challenging to analyze those measurements. Hence, in order to more comprehensively understand these processes, the problem needs to be resolved into the smaller and controllable sub-category of experiments, by creating laminar flamelets. One approach used in creating these flamelets is by establishing simplified non-premixed flames in the counterflow configuration. Alongwith all the fundamental properties of combustion, it is important to study the health hazard and environmentally detrimental emissions, such as soot and polycyclic aromatic hydrocarbons (PAHs). Such combustion studies need to be carried out using the non-intrusive in-situoptical diagnostics measurement techniques, such as the Laser Induced Incandescence (LII), Planar Laser Induced Fluorescence (PLIF) and Light Extinction (LE). These measurements for renewable biofuels aid in better understanding of the soot formation process, as well as in developing the fuel specific knowledge to bring them into commercial use. Furthermore since the most practical combustion systems operate at elevated pressures, it is also important to understand the soot formation process under elevated pressure conditions. Considering these, in the current study, the soot and PAH formation processes for butane and butanol isomers (C4 fuels) at atmospheric pressure; and for ethylene at elevated pressure have been experimentally investigated and compared in a counterflow non-premixed flame configuration.