Hiroyuki Mitsu

Nonlinear optical properties of an organic film formed of dye aggregates with absorption in the telecommunication wavelength range

An organic film formed of newly synthesized dye aggregates with an absorption peak in telecommunication wavelength range exhibited large third-order nonlinear optical susceptibility χ(3) and fast recovery of bleached absorption. A derivative with a di(benzofuranonyl)methanolate structure forms stable aggregates in a spin-coated film and shows an absorption maximum at 1.24 μm. An imaginary part χI(3) of the film assumes a maximum at 1.30 μm, which is −0.83×10−7 esu. The time evolution of differential transmission spectra indicates that the time constant of the recovery of bleached absorption is 80–240 fs for a fast component and 2.2–6.5 ps for a slow one. This organic film has considerable advantages for future planar optical devices.

Ultrafast all-optical switching at 1.55μm using an organic multilayer device

We report ultrafast all-optical switching at optical communication wavelength using a device with a layered structure containing organic films. Spin-coated layers of di(benzofuranonyl)methanolate (BM) derivative are formed alternately with vacuum evaporated layers of germanium (II) oxide. An optical Kerr shutter is constructed using this BM multilayer with 1.55μm signal and 1.63μm gate pulses of 100fs time durations. As a result, optical switching with signal-to-noise ratio over 20dB is attained at gate-pulse intensity above 30pJ∕μm2 and a response time comparable to pulse width is observed. The BM multilayer could be an efficient optical communication device for parallel data processing.

Cadmium telluride bulk crystal as an ultrafast nonlinear optical switch

A semiconductor bulk crystal has several advantages as a nonlinear optical material, such as low processing cost, long interaction length, and alleviation of the free-carrier absorption caused by two-photon absorption (TPA). We examine optical properties of semiconductor bulk crystals with different orientations at 1.55μm and find that CdTe[111] has favorable capabilities, such as nonlinear refractive index of 5.23×10−17(m2W), TPA coefficient of 18.3(mmGW), and consequent figure of merit of 0.54. Optical three-dimensional measurements of reflective material are carried out using CdTe[111] as ultrafast optical Kerr shutter and clear images corresponding to surface steps are obtained.

Terabit all-optical logic based on ultrafast two-dimensional transmission gating

Terabit all-optical complementary logic is proposed using two successive time slots to represent a unique logical status. An organic molecular thin film is used as an array of optically controlled optical switches. By utilizing the planar structure of the film and its ultrafast optical response, proof-of-principle fully optical NOT and AND logic operations were demonstrated with 400-fs interval pulses.

Femtosecond timing measurement and control using ultrafast organic thin films

We show a femtosecond timing measurement and control technique using a squarylium dye J-aggregate film, which is an organic thin film that acts as an ultrafast two-dimensional optical switch. Optical pulse timing is directly mapped to space-domain position on the film, and the large area and ultrafast response offer a femtosecond-resolved, large dynamic range, real-time, multichannel timing measurement capability. A timing fluctuation (jitter, wander, and skew) reduction architecture is presented and experimentally demonstrated.

Skew reduction based on two-dimensional transmission gating using molecular dye film operated at 1.55 μm

All-optical pulse timing fluctuation reduction is successfully demonstrated using a film of organic molecular material, di(benzofuranonyl)methanolate, which is operated at 1.55 mum in an architecture using two-dimensional transmission gating