Photonic Gate Research Articles

Dynamic characteristics of photonic gate with multiple-quantum-well reflection modulator and heterojunction phototransistor

Summary form only given. In order to improve the switching-off speed of a photonic gate array consisting of a multiple-quantum-well (MQW) modulator, a distributed Bragg reflector (DBR), and a heterojunction phototransistor (HPT), a resistor structure connected in parallel with the modulator is proposed. The bandwidth was measured as a function of the optical gain for the following two gate structures: the MQW reflection modulator connected with (1) the p-i-n photodiode in series; and (2) the HPT in series and the resistor in parallel, respectively. The results show that the addition of the resistor can reverse the increase in switching-off time due to the Miller capacitance effect with optical gain. Estimates indicate that optimizing the device size and structure will result in subnanosecond switching times with several times the optical gain. >

Photon-gated spectral hole burning by donor-acceptor electron transfer

We have observed a new mechanism for photon-gated spectral hole burning, donor-acceptor electron transfer, in a material composed of a zinc-tetrabenzoporphyrin derivative (donor) with chloroform acceptors in poly(methyl methacrylate) thin films. Gated holes form when we simultaneously excite the donor 0-0 singlet absorption (630 nm) and the donor triplet-triplet absorption (350-550 nm), with the largest gating enhancement (>30) occurring for gating light near 480 nm. The gating action spectrum and the photoproduct spectrum confirm that the mechanism is electron transfer from an excited triplet of the porphyrin donor to the chloroform acceptor. This result opens up a new class of materials for photon gating that should be of interest for frequency-domain optical storage applications as well as high-resolution spectroscopy of electron transfer processes in solids.