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Nobutaka Hattori,1 Yoshiko Okada,2 Yayoi Kawata,3 Yoshihiko Furusawa,3 Takumi Imai,4 Hisako Yoshida,4 Mihoko Ota,3 Masaki Arai,3 Ayumi Shintani,4 Jovelle Fernandez3 1Department of Neurology, Juntendo University, Tokyo, Japan; 2Japan Parkinson Congress, Tokyo, Japan; 3Japan Medical Office, Takeda Pharmaceutical Company Limited, Tokyo, Japan; 4Department of Medical Statistics, Graduate School of Medicine, Osaka Metropolitan University, Osaka, JapanCorrespondence: Yoshihiko Furusawa, Japan Medical Office, Takeda Pharmaceutical Company Limited, 2 Chome-1-1 Nihonbashihoncho, Chuo City, Tokyo, 103-0023, Japan, Tel +81-3-3278-2111, Fax +81-3-3278-2000, Email yoshihiko.furusawa@takeda.comObjective: The coronavirus disease 2019 (COVID-19) pandemic changed the lives of patients with Parkinson’s disease (PD) and their caregivers. This study aimed to investigate changes in patient behavior and PD symptoms and their effect on caregiver burden resulting from the COVID-19 pandemic in Japan.Methods: This nationwide, observational, cross-sectional survey included patients with self-reported PD and caregivers (members of the Japan Parkinson’s Disease Association). The primary objective was to evaluate changes in behaviors, self-assessed PD symptoms, and caregiver burden from pre–COVID-19 (February 2020) to post–national state of emergency (August 2020 and February 2021).Results: Responses from 1883 patients and 1382 caregivers from 7610 distributed surveys were analyzed. Mean (standard deviation) age of patients and caregivers was 71.6 (8.2) and 68.5 (11.4) years, respectively; 41.6% of patients had a Hoehn and Yahr (HY) scale of 3. Patients (> 40.0%) reported decreased frequency of going out. Most patients (> 70.0%) reported no change in treatment visit frequency, voluntary training, or rehabilitation and nursing care insurance services. Symptoms worsened for approximately 7– 30% of patients; the proportion with HY scale 4– 5 increased from pre–COVID-19 (25.2%) to February 2021 (40.1%). Aggravated symptoms included bradykinesia, walking, gait speed, depressed mood, fatigue, and apathy. Caregivers’ burden increased because of patients’ worsened symptoms and reduced time going out.Conclusion: Control measures during infectious disease epidemics should consider that patients’ symptoms may worsen; therefore, patient and caregiver support is needed to reduce burden of care.Keywords: Parkinson’s disease, COVID-19, questionnaire design, caregiver burden

Two terthiophene–isoindigo copolymers (P3TI-O and P3TI-D) were successfully designed and synthesized. Octyl (O) and dodecyl (D) alkyl side chains were appended at the third position of the first and fourth positions of the last thiophene on the terthiophene donor units in P3TI-O and P3TI-D, respectively. The band gaps of these copolymers were less than 1.7 eV. We found intramolecular charge-transfer states in both copolymers, which were generated with time constants of 4.5 and 13 ps for the copolymers with short and long alkyl side chains on their donor units, respectively. These results indicate that an almost 3-fold faster intramolecular charge-transfer process occurs when the alkyl side chains are shortened by four methyl units. Owing to a better interchain charge transfer, P3TI-O exhibits a more efficient exciton diffusion compared to P3TI-D, thus leading to longer exciton lifetimes in the copolymer with shorter alkyl side chains. Consequently, when blended with PC71BM in bulk heterojunctions, P3TI-O showed a better exciton dissociation efficiency compared to P3TI-D. These results correlate well with the higher short-circuit current densities observed in P3TI-O:PC71BM inverted architecture organic solar cells compared to the P3TI-D:PC71BM ones.

The power conversion efficiency (PCE) of organic solar cells (OSCs) has been gradually increasing over the past years but these emerging photovoltaic devices still suffer from relatively short life...

With the increasing performance of organic solar cells (OSCs), the design of stable donor materials is of paramount importance. In this work, we synthesised a simple alternating copolymer with thiophene and BDT (P3T-BDT) units to understand the impact of incorporation of BDT on the thermal stability of the commonly used thiophene-based OSCs. OSCs fabricated with P3T-BDT:PC71BM and P3HT:PC71BM with 1:4 ratios displayed a different degradation kinetics despite their similar initial power conversion efficiency (PCE). The PCE of P3HT-based device degraded by half while the P3T-BDT-based device lost only 15% of its initial PCE after thermally being degraded at 85 ∘C for 48 h mainly due to the decrease in J s c . Thermally-induced degradation of P3HT caused chain breakage while the P3T-BDT remained intact. The surface morphology of P3HT:PC71BM film exhibited a large increase in roughness in the first few hours leading to a loss of more 40% of its initial PCE while the P3T-BDT based OSC had a similar roughness throughout the accelerated ageing. This is also confirmed by the growth of the PL intensity of P3HT:PC71BM while P3T-BDT:PC71BM remained the same confirming a suppression of demixing of the donor and acceptor in the latter. In summary, the addition a BDT unit in the thiophene-based homopolymer was found to improve the thermal stability thiophene-based OSCs.

A unique photocurrent response of a photovoltaic cell using photosynthetic protein bacteriorhodopsin (bR) is similar to that seen in the retinal ganglion cell, therefore, there are considerable interest in utilizing bR in visual sensors. A position sensitive detector (PSD) is a monolithic photosensor utilizing photodiode surface resistance. When a spot light strikes the PSD, an electric charge proportional to the light intensity is generated at the incident position. This electric charge is driven through the resistive layer and collected by two electrodes as photocurrents, while being divided in inverse proportion to the distance between the incident position and each electrode. In this study, we present 1D 10-cm-long PSD based on bR instead of organic semiconducting polymers. A bR-PSD consists of a dip-coated bR film on a high-resistivity indium-tin-oxide (ITO)-PET film, and counter ITO-PET. The position sensitive output signals of the PSD are measured in response to the intensity-modulated light of a green laser. Nonlinearity, δ=2×RMS deviation/full scale, is a measure of the distortion of the sensor output. An acceptable device has nonlinearities of less than 15%. When the position was detected at a beam diameter of φ = 5 mm, 40 mW/cm2, and the measurement interval 1 mm, the nonlinearity was 3.42%. Especially within an area of position detection error of less than 1%, the nonlinearity was 0.33%. When a beam diameter of φ = 1.5 mm and a measurement interval 500 μm, the nonlinearity showed 0.81% within the range of the light receiving centre of 2 cm. It satisfies 15%, which is the allowable range of general nonlinearity. The bR-PSD showed excellent linearity for all increments measured. Notably, the low cost (3 Euro) and simplicity of fabricating bR-PSD, and no requirement for a bias supply are two of the major advantages over conventional semiconductor material.

β-Carotene (bCar) is a natural organic semiconductor that photo-degrades within a few minutes when exposed to sunlight in ambient conditions and that can be employed as electron donor in organic solar cell (OSC) active layers. Its fast photo-degradation kinetics make bCar an ideal molecule to study strategies to improve the durability of OSCs. Mixing bCar with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) in a 1 : 4 ratio considerably delays the bCar photo-bleaching to produce thin films that are relatively stable when exposed to sunlight for more than an hour. Furthermore, when coated with OSC top electrodes, these active layers exhibit an even stronger resistance again photo-oxidation. Despite the easily photo-oxidized nature of bCar, the resulting bCar:PC71BM OSCs maintain their photovoltaic performances for over 6 months without additional encapsulation and display high thermal stability. In fact, the binary bCar:PC71BM active layers with a large relative concentration of PC71BM exhibit a longer operational stability than reference air-stable active layers in the organic photovoltaic field, namely, poly(2,7-carbazole-alt-dithienylbenzothiadiazole):PC71BM active layers prepared with the same electron donor to PC71BM ratio (1 : 4). The superior durability of bCar OSCs compared to PCDTBT ones can be ascribed to their higher morphological stability which is associated with lower mixing energies in small molecule:fullerene systems with respect to polymer:fullerene ones. Our results thus indicate that small molecule donors combined with PC71BM into active layers have a high potential to produce OSCs that simultaneously achieve high power conversion efficiencies and durability.

Background. The latest Japanese National Curriculum emphasized the importance of active learning as well as communication skills in various subject areas. Following this trend, the social skills education (SSE) approach was adopted to promote and improve skills that facilitate interpersonal conflict resolution in elementary school students. Aim. This study developed a card game to help elementary school teachers perform SSE. The aims were to convince students to contemplate alternative solutions to problems in a way that incorporates suggestions from other students and to motivate children to think about problem solving in a social context. Methods. Our card game was developed based on Matsuda’s warp and woof model of problem-solving that emphasizes generating ideas concerning trade-off resolution in problem-solving. We then tested the game in a sample of 74 fourth grade (9-10 years old) elementary school students. Results. The findings suggest that the students understood the importance of considering new alternatives for trade-off resolution by playing our game. Conclusions. Despite the limitations of our study, such as the small sample size, our findings demonstrated that the game was successful in teaching most students the necessity of reaching a consensus in situations involving conflicting opinions.

β-carotene (bCar) is an abundant natural organic semiconductor that can be extracted from tomatoes or carrots at extremely low costs. Using natural bCar as electron donor combined with a C70 derivative (PC71BM) as electron acceptor in bulk heterojunction active layers, we successfully fabricated efficient inverted organic solar cells (OSCs) processed in air without encapsulation. Unlike conventional OSCs produced with synthetic materials, higher short-circuit current densities are achieved in ultrathin active layers (∼30 nm) compared to thicker ones (∼90 nm). This peculiar behavior can be ascribed to the low hole transport properties of bCar that limit the charge collection efficiency in 90 nm thick bCar:fullerene OSCs. Our results demonstrate that higher boiling point solvents induce crystalline transformation of bCar in thin active layers resulting in OSCs with fill factors around 35% and average power conversion efficiencies (PCEs) of 0.58%. These devices demonstrate stable operation under constant ill...

The receptive field of a visual neuron is the particular region in which a stimulus will modify the firing of that neuron. Retinal ganglion cells have a coaxial-shaped structure formed by the central excitatory and outer inhibitory regions. These regions respond oppositely to light. This shape can be mathematically modeled by a balanced Difference of Gaussian (DOG) function. In digital image processing, the DOG filter is used for detecting objects' edges. Bacteriorhodopsin (bR) is a photosensitive protein which resembles the visual pigment rhodopsin. When bR is illuminated, it generates a positive transient photocurrent, and, when light is switched off, a negative transient photocurrent is produced. This peculiar behavior is similar to the response of ganglion receptive fields. In this study, we fabricate a two-dimensional binarized DOG (b-DOG) filter, in which the central part mimics the excitatory part of the ganglion cell receptive fields, whereas the outer ring reproduces the effect observed in their outer inhibitory regions. This filter consists of photosensitive protein bR films and electrolyte solution that are sandwiched between ITO electrodes. To analyze the spatial-temporal frequency sensitivity, we use moving sine wave gratings with different pitches with a controlled scanning speed. When the temporal frequency is kept constant, the spatial frequency sensitivity matched with the Fourier transform of the b-DOG function. On the other hand, when the spatial frequency does not vary, the temporal frequency sensitivity corresponded well with the Fourier transform of Difference of Gamma function. Difference of Gamma function is known as the impulse response of the visual nerve of animals. We separately analyze the independent spatial and temporal frequencies collected from the spatial-temporal characteristics of the filter. The spatial-temporal frequency characteristics of b-DOG filter are similar to those of the X-type retinal ganglion cells. However, unlike the retinal ganglion cell, the b-DOG filter is a perfect linear filter. The analog image processing using this b-DOG filter is performed by scanning a standard test image. It is found that an edge can be detected just by scanning the image and plotting the zero-crossing point. With increasing input image size, the spatial frequency peak detected by the b-DOG filter shifts towards higher frequencies. Since there are only sharp edges where high spatial frequency components are present, the detected results of the analog filter are similar to that of the digital filter. Consequently, the phase difference between the input and output image is approximately the same for all pixels, and it agrees with the digital edge detection results. Some illusion images are scanned on the b-DOG filter to verify the occurrence of the illusion similar to vision. The Hermann grid illusion generated with lower-order vision was observed. It is found that no luminance information is necessary for the Herman grid illusion, because this b-DOG filter does not extract image luminance. The visual function elements similar to X-type retinal ganglion cells prepared in this study are useful to constructively understand the visual information processing mechanism of the organism.

Optical vortex, possessing an annular intensity profile and an orbital angular momentum owing to its helical wavefront, has been widely investigated in versatile applications, including a laser scanning microscope, optical telecommunication, and optical manipulation. In particular, optical vortex can twist an irradiated material, such as metal, silicon, polymer, and even liquid resin, to form spiral-shaped structured materials on the micro/nano scale [1–3]. The spiralling direction of such structured materials is controlled by the handedness of the optical vortex, i.e. the twisting direction of a helical wavefront. In recent years, a laser-indeed bacteria-waveguide, in which the optical radiation force collects cyanobacteria into the beam to form an optical waveguide [4], has been discovered.

A compact and low-cost motion detector based on a light-sensitive protein bacteriorhodopsin is fabricated. We show that a single photocell, which is masked with a pattern, can detect the speed and direction of a moving light without complex software algorithms. When light scans the patterned sensing area, the edges of each pattern produce polarity-reversed photocurrents depending on the light bar's speed and direction. Owing to the asymmetry of the pattern, we can detect two or four directions of the moving light. We intend to exploit this unique property in gestural manipulation with a laser pointer or fingers for remote control systems.

Bacteriorhodopsin is an attractive photosensitive biomaterial. Its patterns can be obtained via an inkjet printing method. We fabricated Gabor filtering photosensors by layering inkjet patterns, and their sensing characteristics were investigated.

We report the generation of coherent deep ultraviolet light at 199 nm with a maximum average power of 32 mW by frequency quadrupling a picosecond pulse train from a Ti:sapphire laser. Two frequency-doubling stages were taking place in resonant cavities that can enhance conversion efficiency of second harmonic generations (SHGs). To reduce the extra-loss of the resonant cavity, a Brewster-input KBe2BO3F2 (KBBF) prism coupling device (PCD) was designed and employed in the second stage SHG for the first time.

We report on frequency doubling of a single frequency cw Nd:YAG laser at wavelength of 1064 nm using a periodically poled KTiOPO 4 crystal (PPKTP) placed in a single resonant ring enhanced cavity. A maximum output power of 1.23 W, corresponding to 72% of conversion efficiency with 1.7 W of fundamental power, was achieved. This is, to the best of our knowledge, the highest power obtained at this wavelength with PPKTP crystal in an external enhanced cavity. The output power is continuously stable with a peak to peak fluctuation of less than 1% over 4 h owing to optimum design of an enhanced cavity; moreover, the setup is inherently simple and robust. Therefore, it is suitable to be a light source for quantum optics experiments.

We propose ganglion cell receptive-field-type filters with the use of the photoreceptor protein bacteriorhodopsin. Visual image processing is possible with the use of only one sensing element. We also demonstrate that our difference of Gaussians (DOG) filter, which mimics on-center off-suround ganglion cell receptive fields, has the function of a Laplacian filter and can act as an edge detecor. The X-type receptive field responses obtained by the filter, for a variety of stimuli, are compared with available electrophysiological recodings.

We experimentally demonstrated that the excess phase noise of an external cavity diode laser (ECDL) can be efficiently suppressed by optical filtering and resonant optical feedback techniques. A suppression of more than 40 dB phase noise was obtained for the first time using these methods. It made that the phase noise of the ECDL reached shot noise level from 15 MHz. This opens a new way to reduce the phase noise of diode lasers.

Bacteriorhodopsin (bR) is an attractive photosensitive biomaterial which can be exploited for biomimetic sensing. We have developed a novel optical-flow sensing method using a bipolar photosensor array with bR wildtype and its variant (D96N).

EuS nanoparticles were synthesized by the thermal reduction of single source precursor (SSP), (PPh4)[Eu(S2CNEt2)4].2H2O, under microwave irradiation. The average size of the EuS nanoparticles was found to be 8 nm (3-16 nm in size). The organic products on the EuS surface were observed by using FT-IR, NMR, and MS analyses. We have found that these are resulted from the chemical reactions of SSP and cover the nanocrystal surface. A thermal reaction of SSP gave EuS nanoparticles and the organic product (*SCN(Et)2). The organic product would make a dimmer, (Et)2NC(S)-(S)CN(Et)2, by the couping of the radicals formed in the thermal reaction and/or thiopolymer in the solution through the polymerization of the radicals. The effective surface modification by the organic products led to protection of the EuS surface, resulting in the formation of the strongly luminescent EuS nanoparticles at room temperature (emission peak = 350 nm, fwhm = 58 nm, emission quantum yield = 27 +/- 5%).

Local purities of crystal faces of m-chloronitrobenzene (m-CNB) growing from its binary melts containing p-chloronitrobenzene (p-CNB) were measured and were correlated with the local linear growth rates. The local purity is determined from composition of the part of the crystal related to the growth of a certain crystal face. As the result of the experiments, the growth rates in the directions of y -axis and + z -axis are controlled by the presence of p-CNB, and p-CNB was detected in most crystal faces at a variety of levels depending on the crystallographic faces. The existence of the noncrystallizing component (p-CNB) in the crystal was attributed to the inclusion of mother liquor during the growth of crystals. The fractional amounts of inclusions, calculated from the local concentration of p-CNB, were defined as the inclusion factors of each crystal face and were correlated with the local linear growth rates. From the experimental results of local purity, it was found that the faster the crystal face grows the more the purity of m-CNB decreases. With the crystal structure of m-CNB to analyze the molecular arrangements, each face has different characteristic functional group. The linear growth rates of (0 2 0) and rounded faces which have the same functional group were slower than (0 2 1 ) face.

Summary We have experimentally studied about spatial light modulation by using the early photochemical product of bacteriorhodopsin(bR) called K intermediate at room temperature. In general, it is necessary for using K intermediate to lower the temperature of bR under 77 K. In this paper, we propose a new technique to use K intermediate at room temperature. We demonstrated experimentally spatial light modulation by using K intermediate at room temperature.

血液透析歴15年以上の22名を長期透析患者とし, これと年齢, 性, 原疾患を合致させた透析歴2年以上10年未満で無尿の透析患者50名を一般透析患者として, 栄養状態および臨床指標, 透析条件を比較した. また長期透析患者の実際の食事内容を日本腎臓学会の「血液透析患者の食事療法に関するガイドライン」と比較検討した. 一般透析患者との比較では, Kt/V for ureaは一般透析患者1.39±0.25に対し長期透析患者1.63±0.22, またKt/V for β2-microglobulinは一般透析患者0.86±0.44に対し長期透析患者で1.21±0.41で, いずれも長期透析患者で大きかった (p

Second- and third-order non-linear optical properties of C 60 based multilayered charge transfer structures with TPP, TPD and TPN molecules, acting as electron donors, are studied by the transverse optical second and third harmonic generation techniques. The studied structures are of ABABAB… and ABCABC… type, where layer A is made from electron accepting molecules (C 60 ), layer B from electron donating (TPN, TPD or TPP) and layer C from neutral molecules (MgF 2 ). The typical thickness of individual layers is about 2 nm. A significant increase of SHG is observed in ABCABC… type structures, where an effective charge transfer is expected with creation of a non-centrosymmetry in the perpendicular direction to the layers. The largest χ (2) (−2 ω ; ω , ω ) susceptibility is obtained with multilayers containing rubrene (TPN). The SHG generation experiments performed on thin films with different thicknesses show that the non-linear optical response comes from the bulk material and not from the interfaces. A quadratic dependence of SHG intensity on input power is also observed, showing that the charge transfer takes place at the ground state. No increase of third-order NLO response is observed, as compared to the net materials.

A bacteriorhodopsin film is used to measure the electric-field autocorrelation function of picosecond pulses from a mode-locked Nd:YAG laser at 532 nm wavelength. The autocorrelation is performed in geometry of light self-diffraction from polarization as well as intensity gratings at very low average illumination intensity (≈ 6 mW/cm2). By comparing the determined coherence time τC = 5.0 ps with the laser pulse duration τL = 6.6 ps, obtained by the intensity autocorrelation technique, we estimate a chirp parameter of the laser pulse bτL2 = 0.86, which points out rather small phase distortions of the pulse. Broadband absorption of the film in a visible spectral range and a low-cost technology of its preparation, together with the possibility to record polarization and intensity gratings, confirm advantages of the bacteriorhodopsin (BR) film as a novel medium for the field autocorrelation.

The nonlinear optical properties of C 60 -based composites and multilayered charge-transfer structures with 5,10,15,20-tetraphenyl-21 H ,23 H -porphine (TPP) and 5,6,11,12-tetraphenylnaphthacene (rubrene) (TPN) acting as electron donors are studied by transverse optical second- and third-harmonic generation. The results are compared with those obtained on pristine and vacuum-photolyzed C 60 thin films. Second-harmonic generation (SHG) is observed from composite films containing C 60 molecules. A significant enhancement in SHG signal is observed in the multilayered structures. This result is interpreted in terms of a ground state permanent electron transfer from the electron-donating molecules to C 60 . The third-harmonic generation experiments show an enhancement of the cubic susceptibility from vacuum-photolyzed C 60 thin films.

Bacteriorhodopsin (bR) is a promising biomaterial for several applications. Optical excitation of bR at an electrode-electrolyte interface generates differential photocurrents while an incident light is turned on and off. This unique functional response is similar to that seen in retinal neurons. The bR-based bipolar photosensor consists of the bR dip-coated thin films patterned on two ITO plates and the electrolyte solution. This bipolar photocell will function as a biomimetic photoreceptor cell. The bipolar structure, due to the photocurrent being generated in alignment with the cathodic direction, makes the excitatory and inhibitory regions possible. This scheme shows our bipolar cell can act as a basic unit of edge detection and forms the artificial visual receptive field.

Probability distributions of the peak output power from planar microcavity dye lasers with pulsed excitation have been studied experimentally. Two microcavities were used, one operating possibly with a single mode and the other possibly with a number of modes. These expectations are based on the relative magnitude of the mode radius and the pump beam radius. In the former cavity an exponential‐like distribution was observed below threshold, which indicates single‐mode operation. In the latter cavity a single‐peaked distribution appeared even below threshold indicating multiple‐mode operation. These results are, respectively, in qualitative agreement with theoretical distributions for steady state. That the observed pulse width is large enough to apply steady state distribution equation is shown by calculating the characteristic transient time for the intensity distribution.

The experimental rsults concerning the spectral width and angular divergence as well as the mode radius of planar microcavity dye lasers are in agreement with theory for below threshold, but are in discrepancy above threshold with the active mode theory based on the Schawlow-Townes formula.

A novel secure holographic memory system with polarization encoding is proposed. Two-dimensional original data are encoded as a two-dimensional polarization distribution. The polarization state at each pixel is scrambled by a mask that changes the polarization state into a random state. The mask can rotate the direction of the principal axes of the elliptically polarized light and can change the phase retardation at each pixel. The light with the random polarization state is stored as a hologram that can produce the vector phase-conjugate beam. In the decryption the vector phase-conjugation readout can recover the original polarization state by use of the same mask used in the encryption. Experimental results of encryption and decryption with a bacteriorhodopsin film are presented.

We derive an exact dual lattice of a nonlinear version by introducing a double exponential lattice, where not only the interaction potential but also the momentum are of the exponential type. This is the first example of the system with duality in nonlinear systems. The double exponential lattice can be extended to multi-component systems where the parameters characterizing the potential and the momentum are not uniform. In a small-amplitude limit, the double exponential lattice is reduced to the usual exponential lattice. It is shown that the exponential lattice composed of different mass particles is dual to that composed of the interaction with different parameter b in such a limit.

The behaviour of solitary wave has been studied numerically in periodic Toda lattice which has alternate Toda potentials with different parameters. In the numerical calculation, due to deviations from the ideal Toda lattice, the solitary wave decreases in propagation, trailing ripple oscillation behind it. Yet, the stability of the waves depends on the lattice parameters. A narrow solitary wave compared with the lattice constant can propagate stably in the periodic lattice under our special condition. The validity of the K-dV approximation is examined concerning the velocity and width of a small amplitude solitary wave. The duality of nonlinear lattice is also discussed.

We present a convenient method to generate high quality single-frequency green light at a wavelength of 540 nm. It consists of a noise suppressed external cavity diode laser at a wavelength of 1080 nm by optical filtering and resonant optical feedback, and a frequency doubling of the fundamental light with an a-cut KTP crystal. Highly efficient conversion is realized by type II non-critical phase matching. A stable single-frequency operation with a maximum power of about 20 mW is performed for more than 3 h. Both the intensity noise and line-width reach the level of a monolithic nonplanar ring laser, which is well known for its extraordinarily narrow line-width and extremely low noise among available single-frequency operating lasers.

Dichloro(4,4'-dipentyl-2,2'-bipyridine-kappa2N,N')platinum(II), [PtCl2(C20H28N2)], adopts a discrete pi-pi stacking structure, where the alkyl chains are located in a random manner. In contrast, dichloro(4,4'-diheptyl-2,2'-bipyridine-kappa2N,N')platinum(II), [PtCl2(C24H36N2)], forms a layer structure comprised of alkyl chain layers and paired coordination sites, as observed for analogous complexes with longer alkyl chains.

Characteristics of spontaneous and stimulated emission by Eu(BFA)4− chelate in a planar microcavity of 2.5λ length are studied experimentally. The spontaneous emission enhancement factor is close to unity. The observed spectral width and the angular divergence of spontaneous emission are consistent with theory. A distinct threshold for the transition from spontaneous to stimulated emission was observed with an associated decrease in the decay time of the emission. The spectral width decreased with increasing pumping power.

Transmission spectra and photoinduced transmission change are observed in periodic waveguide which consist of a quartz grating substrate and a thin protein film of bacteriorhodopsin. We propose a scheme to achieve all optical switching using the photoinduced refractive index change of bacteriorhodopsin.

It is well known that the centrosymmetric molecules and centrosymmetric materials don’t exhibit, at least within the dipolar scheme, second order nonlinear optical properties useful fore a large class of practical applications, such as frequency conversion through second harmonic generation or parametric processes, light amplification, electro-optic modulation for signal transmission, generation of THz pulses, etc. Therefore a lot of effort was devoted to the design of the highly efficient molecules, with large molecular first hyperpolarizability β tensor and assembling them into a noncentrosymmetric bulk material with optimized χ(2) susceptibility. The first approach is known as molecular engineering and the second as material engineering, respectively [1].

Second and third order nonlinear optical properties of C60 based composites and multilayered structures with TPP and TPN are studied by transverse optical second and third harmonic generation, respectively. The results are compared with those obtained from pristine, photolyzed in vacuum and in oxygen atmosphere C60 thin films. Second harmonic generation is observed from structures containing C60 molecules. An enhancement of the quadratic susceptibility is observed from the multilayered structures. The third harmonic generation experiments show an enhancement of the cubic susceptibility from photolyzed C60 thin films. No increase of (chi) (3) in the multilayered structures or composites is observed. A slightly larger response is obtained with the multilayered thin films as compared to the composite material.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We experimentally demonstrated angular selectivity in a nondestructive readout of a photochromic protein bacteriorhodopsin (bR). bR is a photochromic material which has many unique properties. Especially, its high spatial resolutional recording ability is suitable for holographic applications. From the viewpoint of latching, it is desirable to preserve a hologram after readout. The experimental result shows a weak angular selectivity in a volume hologram on bR.

By frequency quadrupling a picosecond pulse train from a Ti: Sapphire laser with a wavelength of 798 nm and a repetition rate of 82 MHz, we generated a coherent deep ultraviolet light below 200 nm. Two frequency-doubling stages take place in resonant cavities that can increase conversion efficiency. This allows an overall efficiency of 4.3% and produces an output power of up to 60 mW. In the second stage, in which a KBe2BO3F2 (KBBF) crystal was employed as a nonlinear medium, conversion efficiency is increased by about three times compared with that of the single-pass configuration. Taking into account reflective loss, conversion efficiency is improved five times.