Microsecond All-Optical Modulation by Biofunctionalized Porous Silicon Microcavity

We successfully created a composite photonic structure out of porous silicon (PSi) microcavities doped by the photochromic protein, photoactive yellow protein (PYP). Massive incorporation of the protein molecules into the pores was substantiated by a 30 nm shift of the resonance dip upon functionalization, and light-induced reflectance changes of the device due to the protein photocycle were recorded. Model calculations for the photonic properties of the device were consistent with earlier results on the nonlinear optical properties of the protein, whose degree of incorporation into the PSi structure was also estimated. The successful proof-of-concept results are discussed in light of possible practical applications in the future.

All-Optical Switching Demonstrated with Photoactive Yellow Protein Films

Integrated optics (IO) is a field of photonics which focuses on manufacturing circuits similar to those in integrated electronics, but that work on an optical basis to establish means of faster data transfer and processing. Currently, the biggest task in IO is finding or manufacturing materials with the proper nonlinear optical characteristics to implement as active components in IO circuits. Using biological materials in IO has recently been proposed, the first material to be investigated for this purpose being the protein bacteriorhodopsin; however, since then, other proteins have also been considered, such as the photoactive yellow protein (PYP). In our current work, we directly demonstrate the all-optical switching capabilities of PYP films combined with an IO Mach–Zehnder interferometer (MZI) for the first time. By exploiting photoreactions in the reaction cycle of PYP, we also show how a combination of exciting light beams can introduce an extra degree of freedom to control the operation of the device. Based on our results, we discuss how the special advantages of PYP can be utilized in future IO applications.

Complex molecular logic gates from simple molecules

Molecular logic gates (MLGs) are compounds that can solve Boolean logic operations to give an answer (OUTPUT) upon receiving a stimulus (INPUT). These derivatives can be used as biological sensors and are promising substitutes for the present logic gates. Although MLGs with complex molecular structures have been reported, they often show stability problems. To address this problem, we describe herein six stable pseudo-hemiindigo-derived MLGs capable of solving complex logic operations. MLGs 7, 8, 9, and 10 can solve a complex logic operation connecting 4 logic gates using 2 different wavelengths (445 nm and 400 nm) and the presence of p-TsOH and triethylamine (TEA) as inputs; MLG 11 solves a complex logic operation connecting 3 logic gates and uses 3 inputs, one wavelength of 445 nm and the presence of p-TsOH and TEA; and MLG 12 can only solve one logic operation (INH) and uses only the presence of p-TsOH and TEA as an input. Each operating method of the MLGs was evaluated with several techniques; proton interactions with MLGs were screened with NMR by titrating with p-TsOH, the photochemical properties were examined with absorption ultraviolet-visible (UV-Vis) spectroscopy, and the isomerization dynamics were examined with NMR using the two wavelengths for isomerization (photostationary isomer). The results indicate that the pseudo-hemiindigo-derived MLGs described herein can be applied as multiplexers or data selectors that are necessary for the transient flow of information for biological and computer systems. Finally, to design different MLGs and a system that can treat more information as complex logic gates (demultiplexers), two and three MLGs were mixed in different experiments. In both cases, four inputs were employed (445 nm, 400 nm, p-TsOH and TEA), yielding more outputs. Detailed information about the system dynamics was obtained from NMR experiments.

Design of all-optical reversible logic gates using photonic crystal waveguides for optical computing and photonic integrated circuits

Reversible logic gates are capable of designing lossless digital systems, which have received a great deal of attention in photonic integrated circuits due to their advantages, such as less heat generation and low power dissipation. In this paper, all-optical reversible Feynman and Toffoli logic gates are designed for optical computing devices and low-power integrated circuits. Proposed designs of all-optical reversible logic gates are implemented with two-dimensional photonic crystal waveguides without using any nonlinear material. The finite-difference time-domain method is used to simulate and verify the proposed design, and it is operated at a wavelength of 1550 nm. The structure of all-optical reversible logic gates requires much less area, and Feynman logic gates offer a contrast ratio (CR) of 12.4 dB, transmittance of 0.96, and less insertion loss of -0.015dB, while Toffoli logic gates offer a CR of 32.5 dB, transmittance of 0.9, and less insertion loss of -0.04dB.

All-optical design for inherently energy-conserving reversible gates and circuits

As energy efficiency becomes a paramount issue in this day and age, reversible computing may serve as a critical step towards energy conservation in information technology. The inputs of reversible computing elements define the outputs and vice versa. Some reversible gates such as the Fredkin gate are also universal; that is, they may be used to produce any logic operation. It is possible to find physical representations for the information, so that when processed with reversible logic, the energy of the output is equal to the energy of the input. It is suggested that there may be devices that will do that without applying any additional power. Here, we present a formalism that may be used to produce any reversible logic gate. We implement this method over an optical design of the Fredkin gate, which utilizes only optical elements that inherently conserve energy.

Reversible gates, like Fredkin gates, may be useful for energy conservation efforts. Cohen et al. present a formalism that may be used to produce any reversible logic. This method is implemented over an optical design of the Fredkin gate which utilizes only optical elements that inherently conserve energy.

All-optical ultrafast XOR/XNOR logic gates, binary counter, and double-bit comparator with silicon microring resonators

We present designs of all-optical ultrafast YES/NOT, XOR/XNOR logic gates, binary counter, and double-bit comparator based on all-optical switching by two-photon absorption induced free-carrier injection in silicon 2 × 2 add-drop microring resonators. The proposed circuits have been theoretically analyzed using time-domain coupled-mode theory based on reported experimental values to realize low power (∼ 28 mW) ultrafast (∼ 22 ps) operation with high modulation (80%) and bit rate (45 Gb/s). The designs are complementary metal-oxide semiconductor compatible and provide advantages of high Q-factor, tunability, compactness, cascadibility, scalability, reconfigurability, simplicity, and minimal number of switches and inputs for realization of the desired logic. Although a two-bit counter has been shown, the scheme can easily be extended to N-bit counter through cascading.