摘要:

Phase gratings have been recorded in ferroelectric triglycine sulphate crystals doped with iron by interference of two ultraviolet laser beams in the 350 nm wavelength range. The recording sensitivity increases with temperature and a diffraction efficiency exceeding 60% has been reached in a 5.5‐mm‐thick crystal after several hours of writing with intensities of 0.1 W/cm2. The photoinduced refractive index changes are anisotropic. The recording mechanism is not connected with the photorefractive effect and is believed to be due to the redistribution of hydrogen bonds leading to structural and refractive index modifications.

ISSN:0003-6951    

DOI:10.1063/1.102917

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Experimental study of soft x‐ray laser carried out on the LF12 Laser Facility of SIOM (Shanghai Institute of Optics and Fine Mechanics) is reported. Soft x‐ray amplifications were observed in lithium‐like silicon ions by line‐focused laser irradiation of slab targets. Based on the time‐integrated measurements, the gain coefficients are 1.5 and 1.4 cm−1for the 5f–3d(88.9 A˚) and the 5d–3p(87.3 A˚) transitions of lithium‐like silicon ions, respectively. In addition, the spatial characteristics of the laser lines are also presented.

ISSN:0003-6951    

DOI:10.1063/1.102918

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The surface or the Si3N4‐sputtered protective layer of phase change optical recording media was observed with a scanning tunneling microscope. We found the morphology of the protective layer can be controlled by changing the sputtering gas conditions and that overwrite cycle repeatability strongly depends on it. As the Ar gas pressure in the sputtering chamber is decreased, the protective layers become denser and have a flatter surface, and the repeatability is improved from 3×103to 5×105. The media sensitivity also depends on the morphology of the protective layers. The causes of media deterioration after a large number of overwrite cycles are discussed

ISSN:0003-6951    

DOI:10.1063/1.102919

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Insitufully electrical monitoring of the reflectivity of antireflection coatings on semiconductor laser facets is experimentally demonstrated. The operating principle consists of detecting changes in the forward voltage drop induced by the modification of facet reflectivity of a constant current‐driven semiconductor laser. This technique allows one to detect the optimum thickness giving the lowest reflectivity without optical measurement. A reflectivity as low as 1×10−4was currently obtained with electron beam deposited SiOxfilms on 1.5 &mgr;m buried ridge stripe lasers.

ISSN:0003-6951    

DOI:10.1063/1.102920

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Visible photoluminescence was observed in ultrafine Si particles at room temperature. Transmission electron microscopy revealed that Si microcrystallites were embedded in a Si oxide matrix for the sample which emitted the light. The emission energy depended on crystallite size in the range from 2.8 to 5 nm. The inverse relation between emission energy and the square of the crystallite size indicates that carrier confinement in the Si microcrystallites causes this photoluminescence phenomenon.

ISSN:0003-6951    

DOI:10.1063/1.102921

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have fabricated fiber‐compatible, low‐loss, wavelength and polarization insensitive 3 dB 2×2 cross couplers by Ag+‐Na+ion exchange in glass. The couplers were designed using the adiabatic invariance condition for graded‐index channel waveguides. An excellent agreement between theory and experiment is demonstrated.

ISSN:0003-6951    

DOI:10.1063/1.102922

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A planarity preserving method for the definition of vertical‐cavity surface‐emitting lasers (VC‐SEL) is described. A strained‐layer InGaAs quantum well VC‐SEL structure was grown and lasers were laterally defined using a tailored deep proton implantation process. In these lasers we obtained low threshold current densities of 1000 A/cm2and efficient cw operation. This method facilitates large‐scale integration of VC‐SEL devices.

ISSN:0003-6951    

DOI:10.1063/1.102923

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We examine the effects of avalanche processes on several classes of nonlinear optical interactions in semiconductor junctions. A silicon avalanche photodiode (APD) geometry is predicted to provide large enhancements of both the electronic nonlinearity (free‐carrier plasma interaction) as well as the thermal nonlinearity. The thermal nonlinearity at a wavelength &lgr;=1.06 &mgr;m in an APD is examined under normal operating conditions and a nonlinear interaction more than 5000 times that of the unbiased diode is observed.

ISSN:0003-6951    

DOI:10.1063/1.102924

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A passively mode‐locked, flashlamp‐pumped Nd:YAG laser with a cavity length of 11.19 m has been developed to study the noncontact generation of narrow‐band ultrasound. The individual mode‐locked pulses acted as separate sources of ultrasound, producing a train of acoustic pulses with a repetition rate of about 13.4 MHz. The ultrasound was generated in an aluminum sample and remotely detected with a path stabilized Michelson interferometer. The energy in the multiple pulse acoustic signal was confined to a considerably reduced spectral range compared with that in a single pulse.

ISSN:0003-6951    

DOI:10.1063/1.102925

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Hydrogen (H) plasma irradiation effect on (100)  GaAs surfaces was studied. The etching of GaAs surfaces was found to be effectively ceased after some etch at the initial stage when the plasma beam was incident on the surface at a shallow glancing angle. The etched surface was an atomically flat (100)  GaAs surface as previously observed by clear Laue spots in the reflection high‐energy electron diffraction measurement reported by I. Suemune, Y. Kunitsugu, Y. Kan, and M. Yamanishi [Appl. Phys. Lett.55, 760 (1989)]. A physical model for the newly found relation between the etch rate and the surface structure is discussed.

ISSN:0003-6951    

DOI:10.1063/1.102926

出版商:AIP    

年代:1990

数据来源: AIP