We propose an optical parallel adder based on a binary decision diagram that can calculate simply by propagating light through electrically controlled optical pass gates. The CARRY and CARRY operations are multiplexed in one circuit by a wavelength division multiplexing scheme to reduce the number of optical elements, and only a single gate constitutes the critical path for one digit calculation. The processing time reaches picoseconds per digit when we use a 100-μm-long optical path gates, which is ten times faster than a CMOS circuit.
High-performance and low-cost sensors are critical devices for high-throughput analyses of bio-samples in medical
diagnoses and life sciences. In this paper, we demonstrate photonic crystal nanolaser sensor, which detects the adsorption
of biomolecules from the lasing wavelength shift. It is a promising device, which balances a high sensitivity, high
resolution, small size, easy integration, simple setup and low cost. In particular with a nanoslot structure, it achieves a
super-sensitivity in protein sensing whose detection limit is three orders of magnitude lower than that of standard
surface-plasmon-resonance sensors. Our investigations indicate that the nanoslot acts as a protein condenser powered by
the optical gradient force, which arises from the strong localization of laser mode in the nanoslot.
In photonic crystal (PC) microlasers with point defect cavities, effective carriers are reduced by the leakage to outside of the defect, surface recombination, spatial carrier hole burning, and Auger recombination. To estimate these effects, we calculated carrier and photon behavior by solving two-dimensional rate equations in space and time domains. The result clearly shows these effects and their dependence on cavity structure, pump area, and so on. Compared with that for the microdisk laser, higher threshold values are estimated for PC microlasers. However, a comparably low threshold density and a high efficiency are expected for the quasiperiodic PC microlaser, because the hole burning by the whispering gallery mode of this cavity suppresses the carrier leakage.
The recent development of photopumped 1.5 - 1.65 μm GaInAsP microdisk, microgear and photonic crystal lasers is re-viewed. For the former two lasers, room temperature cw lasing characteristics are presented. Their small cavity volume and high Q factor simply reduced the threshold pump power to a record low value of 10 microwatt order, and provided a large sponta-neous emission factor of over 0.1 potentially with the Purcell effect. In the microdisk, nonlasing resonant modes with differ-ent order and different phase often appear. Rate equation analysis indicated that such modes with a high Q affect the laser performance. The microgear having a rotational periodic structure is unique because it not only suppresses such modes, but also increases the Q factor by the minute control of electromagnetic fields so that the radiation field is minimized. The latter advantage will allow a further reduction in cavity size from the smallest limit of the microdisk. A couple of microdisks lased even in a form of a coupled cavity, which can be treated as a photonic molecule. The photonic crystal cavity is also unique because it is easy to construct various types of cavities by the composite of line and point defects inside the uniform photonic crystal slab. The pulsed lasing was obtained in some of them, while we found a large thermal resistance that dis-turbed the cw lasing. We also found through the rate equation analysis that carriers are effectively confined in the microdisk by the strain relaxation effect in compressively-strained quantum wells. However, the result also suggested that the carrier confinement is rather degraded by this effect, so a structural optimization is necessary in the photonic crystal laser.