Biomaterial-Based Biomimetic Visual Sensors: Inkjet Patterning of Bacteriorhodopsin.

Biomimetic visual sensors utilizing bacteriorhodopsin (bR) were fabricated by using an inkjet method. The inkjet printer facilitated the jetting of the bR suspension, allowing for the deposition of bR films. The resulting inkjet-printed bR film exhibited time-differential photocurrent response characteristics similar to those of a dip-coated bR film.

Experimental observation of three-photon interference between a two-photon state and a weak coherent state on a beam splitter.

We experimentally demonstrated a three-photon interference on a beam splitter between a weak coherent state and a two-photon state produced by a spontaneous parametric down conversion. It indicates that a combined three-photon probability amplitude, which is formed by the two-photon state and one-photon from the coherent state, can be used to interfere with another three-photon probability amplitude from the coherent state. The observed three-photon coincidence rate showed that the interference depended on not only the relative phase between the two interference field but also the amplitude of the weak coherent state.

Controlling quantum interference in phase space with amplitude.

We experimentally show a quantum interference in phase space by interrogating photon number probabilities (n = 2, 3, and 4) of a displaced squeezed state, which is generated by an optical parametric amplifier and whose displacement is controlled by amplitude of injected coherent light. It is found that the probabilities exhibit oscillations of interference effect depending upon the amplitude of the controlling light field. This phenomenon is attributed to quantum interference in phase space and indicates the capability of controlling quantum interference using amplitude.

Development of UV Light Irradiation Patterning of Bacteriorhodopsin Thin Films for Biomimetic Functional Devices.

We developed a new patterning method for bacteriorhodopsin (bR) thin films using UV light irradiation. The proton pump function of bR thin films can be deactivated with UV light irradiation. Inactivation of the proton pump function of bR is related to structural changes or photo-bleaching of the retinal in bR using UV light exposure, which was confirmed with absorption and Raman spectroscopy measurements.

Enhanced Photocurrent Generation from Bacteriorhodopsin Photocells Using Grating-Structured Transparent Conductive Oxide Electrodes.

We fabricated a grating-structured electrode made of indium-doped zinc oxide (IZO) with a high refractive index (approximately 2) for a bacteriorhodopsin (bR) photocell. We investigated the photocurrent characteristics of the bR photocell and demonstrated that the photocurrent values from the bR/IZO electrode with the grating structure with a grating period of 340 nm were more than 3.5-4 times larger than those without the grating structure.

Investigation of the photon-number statistics of twin beams by direct detection.

We present the results of an experiment in which we observed photon-number statistics of twin beams emerging from a nondegenerate optical parametric oscillator. We generated the photocurrent for recording by detecting the light and mixing it with a standard electrical oscillator. The measured photocurrent variances exhibited a quantum correlation of as much as -4.

Generation of two-mode bright squeezed light using a noise-suppressed amplified diode laser.

We present the generation of nonclassical state using an amplified diode laser as a light source. The intensity noise of an amplified diode laser was significantly suppressed and reached the shot noise limit at 15 MHz using both a filter cavity and resonant optical feedback. Frequency doubling efficiency of 66% and up to 120 mW output power of green has been achieved in cw second-harmonic generation from 1080 nm to 540 nm.

Generation of twin beams from an optical parametric oscillator pumped by a frequency-doubled diode laser.

Quantum-correlated twin beams were generated from a triply resonant optical parametric oscillator with an a-cut KTP crystal pumped by a frequency-doubled diode laser. A total output of 5.1 mW was obtained in the classical-nonclassical light-conversion system driven by a 50-mW diode laser at 1080 nm.

Generation of 22.8 mW single-frequency green light by frequency doubling of a 50-mW diode laser.

We report frequency doubling of an extended-cavity diode laser in an a-cut KTP crystal. Continuous-wave, single-mode green light at 540 nm with a power of 22.8 mW was generated from an input of 44.

Quantum channel using photon number correlated twin beams.

We report quantum communications channel using photon number correlated twin beams. The twin beams are generated from a nondegenerate optical parametric oscillator, and the photon number difference is used to encode the signal. The bit error rate of our system will be 0.

Experimental investigation of the intensity fluctuation joint probability and conditional distributions of the twin-beam quantum state.

We give the intensity fluctuation joint probability of the twin-beam quantum state, which was generated with an optical parametric oscillator operating above threshold. Then we present what to our knowledge is the first measurement of the intensity fluctuation conditional probability distributions of twin beams. The measured inference variance of twin beams 0.