Thermal probing in single microparticle and microfiber induced near-field laser focusing.

Microparticle and microfiber induced near-field laser heating has been widely used in surface nanostructuring. Information about the temperature and stress fields in the nanoscale near-field heating region is imperative for process control and optimization. Probing of this nanoscale temperature, stress, and optical fields remains a great challenge since the heating area is very small (~100 nm or less) and not immediately accessible for sensing. In this work, thermal probing of a single microparticle and microfiber induced near-field focusing on a substrate with laser light is conducted experimentally and interpreted by high-fidelity simulations. The laser (λ = 532 nm) serves as both heating and Raman probing sources. It is very interesting to note that variation of the Raman intensity, wavenumber, and linewidth all can be used to precisely capture the size of the micro-size subject on the substrate. Nanoscale mapping of conjugated optical, thermal, and stress effects, and the de-conjugation of these effects are performed. The effect of the laser fluence on the temperature and stress in the nanoscale heating region is investigated. With laser fluence of 3.9 ×10(9) W/m(2) and for a 1.21 μm silica particle induced laser heating, the maximum temperature rise and local stress are 58.5 K and 160 MPa, respectively. For a 6.24 μm glass fiber, they are 33.0 K and 120 MPa, respectively. Experimental results are explained and consistent with three-dimensional high-fidelity optical, thermal and stress field simulation.