Photo-optic Effects Research Articles

Fabrication of an amorphous As2S8 stripe waveguide and its optical stopping effect

Amorphous As2S8 chalcogenide glass is shown to undergo changes in refractive index upon exposure to ultraviolet (UV) light. As2S8 film properties are studied, which were measured with testing techniques of prism coupler, x-ray diffraction spectrum and Raman spectra. It is found that the refractive index increases and the thickness decreases after UV light irradiation. The visible optical absorption spectra show that photo-darkening does not exist in the As2S8 film. Based on the study of these phenomena, the UV light irradiation technique is presented and employed for fabricating an As2S8 stripe waveguide, which is shown to be an effective guided mode device with a useful switching functionality based on the photo-optical effect, such as an all-optical attenuator.

Fabrication of an As2S8 stripe waveguide with an optical stopping effect by exposure to ultraviolet irradiation

Amorphous As2S8 chalcogenide glass is shown to undergo changes in the refractive index upon exposure to ultraviolet light. This phenomenon is employed to fabricate an As2S8 stripe waveguide, which is shown to be an effective guided mode device with a useful switching functionality based on the photo-optical effect.

Optical-stopping effect of As2S8 channel waveguide fabricated by method of photoinduced refractive index changes

The photorefractive phenomenon of As2S8 film is reported in this paper. An ultraviolet irradiation technique is presented and applied successfully to As2S8 channel waveguide preparation on the basis of analyzing these experimental data. This channel waveguide of As2S8 displays good characteristics of a waveguide using a guided mode excitation. It is found that the optical stopping effect of As2S8 channel waveguide has the rotential application owing to its switching function with the photo-optical effect.

Dynamics of Photo-Optical Effect of Azo Dyes Measured with Michelson Interferometer

Controlling refractive index of materials is important for optical processing system. Especially, photochromic reactions are one of the potential techniques which induce irreversible refractive index change in materials. The photochromic reactions are usually performed in the solid state because of the applications to devices. However, the kinetic and the reactivity of the photochromism are basically different from those in solution. We measured the dynamics of refractive index change of photochromic dyes by a Michelson interferometer.

Internal Friction and Photoacoustic Effects in A2B6 and A2B7(HgI2) Single Crystals at Different Levels of Ultrasound Strain Amplitude

A comparison of effects in damping and Young modulus under the influence of illumination for ZnSe and HgI 2 demonstrates quite different mechanisms of photoacoustic interaction in the crystals: a drift of photocarriers in the electric field which arises due to piezoelectricity for the first case and a dislocation pinning mechanism for the second one. Spectral responses of the photoacoustic effect in both amplitude independent and dependent damping range are presented for mercury iodide crystals. The newly found acousto- and photo-optic effects in the luminescence spectrum of HgI 2 allow one to specify the photosensitive dislocation pinning centre as an exciton state of carriers on a stoichiometric point defect of the lattice (iodine ur mercury vacancy or interstitial).

Photo-optical effect of polymers containing norbornadiene moieties.

Refractive indices of films containing NBDA and QCA, and photoinduced refractive index changes of films containing norbornadiene moiety were measured, and the applicability of these materials to optical waveguide lithography was examined. Refractive indices of PMMA films containing QCA were smaller than those of PMMA films containing NBDA due to the difference of molar refractions between NBDA and QCA. Photoinduced refractive index change was measured for a P(NBDA/mXDA) film. The refractive index decreased as photochemistry proceeded keeping wide transparent wavelength region.

Molecular beam epitaxy engineered III-V semiconductor structures for low-power optically addressed spatial light modulators

Device approaches are investigated for optically addressed SLMs based on molecular-beam epitaxy (MBE) engineered III-V materials and structures. Strong photooptic effects can be achieved in periodically delta-doped multiple-quantum-well structures, but are still insufficient for high-contrast modulation with only single- or double-pass absorption through active layers of practical thickness. The asymmetric Fabry-Perot cavity approach is employed to permit extinction of light due to interference of light reflected from the front and back surfaces of the cavity. This approach is realized with an all-MBE-grown structure consisting of GaAs/AlAs quarter-wave stack reflector grown over the GaAs substrate as the high reflectance mirror and the GaAs surface as the low reflectance mirror. High-contrast modulation is achieved using a low-power InGaAs/GaAs quantum well laser for the control signal.

Optically addressed spatial light modulators by MBE-grown nipi MQW structures

Promising approaches for achieving optically addressed spatial light modulators (O-SLMs) are investigated based on combining nipi and multiple quantum well structures. Theoretical aspects of photooptic effects achievable in such structures are treated. Test structures are grown by molecular beam epitaxy using two material systems, (In,Ga)As/GaAs and (Al,Ga)As/GaAs. Experiments show large optically controlled modulation of the absorption coefficient in the quantum well layers ( approximately 10(4) cm(-1)), a log power dependence on the control signal, millisecond and shorter time response, and generally predictable behavior. The results are encouraging for several different O-SLM device structures proposed.

On the intrinsic nature of photocontraction effect in Ge-Se films

The nature of the gaint photocontraction effect observed in obliquely deposited thin films of Ge-Se has been investigated by various analytical techniques. It has been established that the observed contraction is entirely an intrinsic photooptical effect as long as the temperature during exposure does not exceed 80°C. At elevated temperatures, thermal evaporation, photooxidation and photoevaporation of selenium in the films takes place.