Single functional molecules offer great potential for the development of novel nanoelectronic devices with capabilities beyond today's silicon-based devices. To realise single-molecule electronics, the development of a viable method for connecting functional molecules to each other using single conductive polymer chains is required. The method of initiating chain polymerisation using the tip of a scanning tunnelling microscope (STM) is very useful for fabricating single conductive polymer chains at designated positions and thereby wiring single molecules. In this feature article, developments in the controlled chain polymerisation of diacetylene compounds and the properties of polydiacetylene chains are summarised. Recent studies of “chemical soldering”, a technique enabling the covalent connection of single polydiacetylene chains to single functional molecules, are also introduced. This represents a key step in advancing the development of single-molecule electronics.

The Hamiltonian and the equations of motion for various modes involving spontaneous and stimulated Raman processes are derived. The coupled differential equations involving these modes are solved analytically by using an intuitive approach (IA). The solution of the present paper does not require any short time approximation. As a matter of fact, the present solution for field operators and hence the squeezing for various modes are valid for all interaction time t. In this way, the present paper is more general compared to the earlier investigations where short-time approximations were found a must. By exploiting the solutions for the field operators, we obtain the squeezing effects of input coherent light for pure and for mixed field modes. The IA employs the perturbation theory and hence we came across the secular terms in the solution. Of course, for small coupling constants these secular terms could be summed for all orders. To establish our claim, we remove the secular terms at least for one occasion.