We report on the design, fabrication and integration of micro/nano-scale optical waveguide arrays and devices for optical printed circuit board (O-PCB) and VLSI photonic applications. The O-PCBs perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards or chips in a manner similar to the electrical printed circuit boards (E-PCBs). The photonic devices include microlasers, microlenses, micro-reflectors, couplers, arrayed waveguide grating structures, multimode interference (MMI) devices and photodetectors. For VLSI micro/nano-photonics we used photonic crystals and plasmonic metal waveguide structures. We also describe device characterization using near filed scanning microscopy. We examine the scientific and technological issues concerning the miniaturization, interconnection, and integration of photonic devices, circuits and systems in micron or submicron scale. In miniaturization, the issues include size effect, proximity effect, energy confinement effect, microcavitiy effect, single photon effect, optical interference effect, high field effect, nonlinear effect, noise effect, quantum optical effect, and chaotic noise effect. In interconnection, the issues include homogeneous interconnection (between identical devices) and heterogeneous interconnection (non-identical devices). In integration, the issues of interfacing same kind of devices, two different kinds of devices, and several or many different kinds of devices are addressed. The discussion includes the nano-scale electron beam system and techniques to characterize nano-scale structures.