Optical technology is rapidly finding novel applications in several exiting bioanalytical, biological, and biomedical applications. Optical beams are increasingly used for bio-fluidic sample manipulation in BioMEMS devices replacing convectional mechanical, electrostatic, and electrokinetic methods. This paper presents novel multiphysics computational approach for modeling optical interaction with fluidic, thermal, mechanical, and biological processes. We present a model of optical manipulation of particles and biological cells with laser beams. Computational results are compared to available experimental data from laboratory experiments and from practical engineered optical bio microdevices. The modeling approach is demonstrated on selected specific applications of optical manipulation of micro spheres, micro cylinders, and optical manipulation and sorting of biological cells in microfluidic cytometers.