摘要:

Second harmonic generation (SHG) has been studied in a nitro‐substituted ferroelectric liquid crystal cooled from the smectic‐C* into a three‐dimensional crystalline (K) phase in an applied electric field. The SHG efficiency in theKphase is found to bedeff≳4.5 pm/V, about 25 times the value in the SmC* phase, and, unlike the SmC* case, remains constant in zero field for ≳25 h. A quantitative analysis of the polarization dependence of the SHG reveals that the dominantdcoefficients contributing to the measured signal differ for the two phases, and that the orientation of the liquid‐crystal director in theKphase is modulated in one dimension. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113648

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The retracing behavior of the phase‐matching angle (RBPA) in optical parametric generation (OPG) based on a LiB3O5(LBO) crystal and pumped at 532 nm by a frequency doubled, passive‐active mode‐locked Nd:YAG laser is investigated. Two pairs of radiations, which are simultaneously generated in the OPG, are observed and the spectral radiant power of the four tunable beams are obtained, showing good agreement with the theoretical calculation results. Together with the parametric process, two kinds of frequency‐mixing waves are produced and this novel multiwavelength interaction phenomenon is analyzed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113649

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Fabrication of optical waveguides on LiNbO3by Zn diffusion from the vapor phase has been demonstrated, using a specially designed diffusion apparatus. The planar waveguides onz‐cut samples support both TE and TM propagations, indicating an increase of refractive indices forn0andne. Energy dispersive x‐ray analysis measurements confirm the diffusion of Zn into the crystal, and analysis of the content of Zn as a function of diffusion depth for samples treated at different temperatures indicates much higher diffusion coefficients than those obtained for Ti diffusion in LiNbO3. The technique is versatile, easy to operate, and allows fabrication of waveguides at temperatures as low as 600–700 °C, thus preventing Li outdiffusion. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113650

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The correlation between the optical properties and composition of lithium niobate films is investigated in films deposited by laser ablation of single‐crystal LiNbO3and Li enriched LiNbO3sintered targets under different oxygen pressures and laser fluences. The results show that the variation of the film refractive index is in many cases related to the deposition process itself, rather than to a variation of the film composition. The experimental conditions to produce stoichiometric films with optical properties similar to those of the bulk material are discussed. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113651

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Simple II–VI laser cavities were formed by cleaving epitaxial ZnSe samples containing a single CdSe quantum well of mean thickness about 1 monolayer. Time‐integrated stimulated emission spectra of these lasers show little evidence of mode structure. A video camera enables temporal resolution of the stimulated emission spectra. Mode structure appears on the time‐resolved spectra. In addition, however, video spectroscopy reveals spatial variations of wavelength and intensity in the laser output which are not well understood. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113652

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An analytical solution to the problem of nondegenerate four wave mixing in a semiconductor optical amplifier emphasizing operation with short optical pulses is described. Calculated conversion efficiencies for pulses are significantly larger than for cw fields and are pulse width dependent. Conditions for optimum conversion efficiencies in terms of the pump input energy and the relative temporal alignment between the pulses are presented. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113653

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Integrated optics evanescent wave sensors suffer from attenuation losses and reduced contrast ratio when the sensing layer index is too close to the waveguide index. This is attributed to an increase in mode mismatch at inner interfaces of the devices. By properly balancing the losses on each arm of an integrated Mach–Zehnder the contrast ratio is increased to nearly 100% on the entire index range, furthermore, a new technique used to make a smooth transition between sensing and nonsensing waveguides reduced the losses by 5 dB. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113654

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photochemical laser‐induced deposition of silicon dioxide thin films is reported with excimer laser radiation at 248 nm. A deposition rate of 0.25 A/pulse was obtained at room temperature. The deposited films were characterized by scanning electron microscopy, x‐ray photoelectron spectroscopy, ellipsometry and optical microscopy. The films exhibited excellent properties (n=1.47,k=0.05) derived from ellipsometry data. The deposition required no oxidizing coreactant. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113655

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

On laboratory scale a new nondestructive technique has been elaborated for the quality control of layered structures. This technique is called the ‘‘acousto‐optic technique’’ and it measures the modulation of ultrasound reflected by a layered material optically in amplitude and phase using laser beams crossing the ultrasonic beams (incident and reflected). The most important characteristics of layered structures which have been investigated are the thickness and the thickness variations within a layer and the presence of artificial defects. Only when the ultrasound is incident in the Rayleigh angle of the substrate material, the phase differences measured obtain important information on the quality of the layered structure. The experimental results underline the results already obtained from the theoretical models elaborated for this technique. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113656

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A novel dual laser ablation process that leads to particulate‐free film growth is presented. A pulsed CO2laser and an excimer (KrF) laser have been spatially overlapped on a Y2O3target with a temporal delay between the pulses. The particulate density of the films grown by this method are at least three orders of magnitude smaller than the particulate density of a single excimer laser ablated film of similar thickness. In addition, a time‐of‐flight ion probe study indicates a sixfold enhancement of the plume species kinetic energies under dual‐laser ablation. The degree of the plume excitation is observed to depend strongly on the delay between the laser pulses. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113657

出版商:AIP    

年代:1995

数据来源: AIP