GaAs-based micromachining is a very attractive technique for integrating mechanical structures and active optical devices, such as laser diodes and photodiodes. For monolithically integrating mechanical parts onto laser diode wafers, the micromachining technique must be compatible with the laser diode fabrication process. Our micromachining technique features three major processes: epitaxitial growth (MOVPE) for both the structural and sacrificial layers, reactive dry-etching by chlorine for high-aspect, three-dimensional structures, and selective wet-etching by peroxide/ammonium hydroxide solution to release the moving parts. These processes are compatible with laser fabrication, so a cantilever beam structure can be fabricated at the same time as a laser diode structure. Furthermore, a single-crystal epitaxial layer has little residual stress, so precise microstructures can be obtained without significant deformation. We fabricated a microbeam resonator sensor composed of two laser diodes, a photodiode, and a micro-cantilever beam with an area of 400700 µm. The cantilever beam is 3 µm wide, 5 µm high, and either 110µm long for a 200-kHz resonant frequency or 50 µm long for a 1-MHz resonant frequency. The cantilever beam is excited by an intensity-modulated laser beam from an integrated excitation laser diode; the vibration signal is detected by a coupled cavity laser diode and a photodiode.

We studied Si and Mg doping characteristics in cubic GaN and fabricated a light emitting diode of cubic GaN on a GaAs substrate by metalorganic vapor-phase epitaxy. The diode structure consisted of undoped and Mg-doped GaN stacking layers deposited on Si-doped GaN and AlGaN layers. The electron-beam-induced-current signal and current injection characteristics of this diode structure were measured. There was a peak at the interface between the Mg-doped and undoped GaN in the electron-beam-induced-current signal. This shows successful growth of the p-n junction. Light emitting operation was achieved by currents injected through the conducting GaAs substrate of this diode at room temperature. We observed electroluminescence below the bandgap energy of cubic GaN with a peak at 2.6 eV.

A thermally controlled magnetization actuator (TCMA) is proposed for micro-mechanical relays. It is actuated by changing the local magnetization of the structure by remote heating using a laser beam. It is fabricated by nickel surface micromachining (a fabrication technique using nickel electroplating). The optical power of the laser diode used to drive the TCMA is about 30 mW. The switching time of the microrelay was experimentally measured to be 10 ms, the same as that of a conventional mechanical relay. The contact force was calculated to be 20 µN, which can be improved by increasing the size of the TCMA.

Some sampled servo signal characteristics of an optically switched laser diode (OSL) head are examined. Wobbling signal amplitude increases with bias current and is proportional to the light beam deviation from a track center at around the threshold current corresponding to the low reflection part of the medium. It is confirmed that OSL head tracking can be realized using the sampled servo method.