摘要:

Resonant modulation of asinglecontact semiconductor laser at the cavity roundtrip frequency of 40 GHz is demonstrated. Efficient mode coupling is obtained with a single contact device by utilizing the high attenuation of the millimeter‐wave modulation signal along the laser stripe. The properties and limitations of this technique are analyzed using a distributed circuit model of the laser. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113930

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We demonstrate a method of permanent optical recording of digital data which exploits a fast photoisomerization of nonlinear molecules, followed by a slow permanent alignment within a polymer. Write and erase cycles are initiated by rapidly photoisomerizing azobenzene molecules into an intermediate state with a larger mobility. The molecules align or randomly orient within the polymer depending on the presence or absence of an electric field. During orientation, relaxation to a stable isomer occurs and the alignment becomes permanent. The recorded information can then be nondestructively read by second‐harmonic generation. Nanosecond optical exposures were used, demonstrating that extremely fast recording rates are possible. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113931

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have demonstrated second‐harmonic generation in a GaAs/AlAs vertical cavity grown on a (311)B GaAs substrate. Second‐harmonic light of 492 nm was observed and its efficiency was measured to be 1.4×10−4%/W. The cavity confines high intensity of fundamental field, resulting in efficient second‐harmonic generation. Quasiphase matching was realized with the stacked GaAs/AlAs layers inside the cavity, which was designed taking into account the strong absorption of second‐harmonic power in GaAs layers. We show that conversion efficiency of the GaAs/AlAs vertical cavity could be more than 10%/W if the optimization is completed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113932

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The frequency of a commercial Ti:sapphire laser is stabilized directly relative to the Lamb‐dip signal from an atomic vapor cell without the Fabry–Pe´rot cavity as in intermediate frequency reference. The laser spectrum is measured by means of a supercavity spectrum analyzer with a full width at half‐maximum (FWHM) of 110 kHz, which is independently calibrated using a ring‐down technique. The measured spectrum has a FWHM of 220 kHz, thus indicating the laser linewidth to be about 55 kHz RMS. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113933

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

By using the second harmonic generation (SHG) microscope, which we have recently developed, two‐dimensional images of ferroelectric domain structure were successfully obtained by exploiting the inhomogeneous distribution of the quadratic nonlinear optical constant in specimens. 90° domain structure ofBaTiO3was observed with intensity contrast of the second harmonic wave. A periodically inverted antiparallel domain inLiTaO3was also observed. This fact indicates that the SHG microscope provides a new method of observing antiparallel ferroelectric domain structure in a nondestructive way, which is especially important for characterizing the quasiphase matched devices for compact blue light lasers. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113934

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A simple interferometric technique is described which can be used to accurately measure the phase response of waveguide grating filters. A narrowband, tunable Ti:sapphire laser is used in a Michelson interferometer configuration, where light reflected from a waveguide grating filter is combined with a reference beam. The intensity of the combined beams is measured as the wavelength of the Ti:sapphire laser is tuned. The measured intensity exhibits a quasisinusoidal wavelength dependence, from which the phase response of the filter can be deduced. This method is successfully demonstrated using both an integrated optic waveguide grating filter and a bulk grating pair. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113935

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have investigated the effect of mismatch between the reflectivity resonance and the gain spectra of vertical cavity surface emitting lasers. Detuning was caused by hydrostatic pressure and self‐heating. Hydrostatic pressure shifts the gain peak towards shorter wavelengths with respect to the Fabry‐Pe´rot (FP) resonance without modifying the gain spectrum. The threshold current remained unchanged for a positive mismatch of up to 18 nm. It increased four‐fold for a negative mismatch of −13 nm at 0.5 GPa, where lasing disappeared. Increased threshold current and quenching of the emission are a consequence of the decrease of the gain at the FP resonance. A similar effect was observed when the gain peak was red‐shifted with respect to the FP resonance by increasing the injected power. Increased mismatch is accompanied by a decrease of the gain at the emission wavelength which is responsible for the laser output quenching at high injected powers. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113936

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The photoinduced isotropic and anisotropic changes in the refractive index of dye/polymer guest‐host systems are investigated. The values obtained are compared to the diffraction efficiencies of scalar and polarization holographic gratings, recorded in the same polymer systems. It is concluded that the induced anisotropy is related to the dye molecules involved in the photoprocesses, whereas the isotropic changes, which are much stronger, are related to the polymer matrix as well. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113937

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Insituthin film thickness measurement is an important problem in semiconductor processing, which is currently limited by the lack of adequate sensors. Most of today’s available techniques are restricted to certain type of films and many have difficulties in performing the measurementinsitu. The fact that the velocity of an ultrasonic Lamb wave traveling in a silicon wafer is changed by the thin film coating on the wafer surface can be used as a monitoring method for basically any type of film—opaque, transparent, metal, or insulator. The acoustic sensors are easily implemented into plasma or CVD environments. We have demonstrated the technique in an aluminum sputtering system in which we measure Al film thickness with a resolution of ±100 A˚. Even better resolution can be achieved for SiO2, copper, and tungsten films. This system has a variety of potential applications, not only in film thickness measurement, but also in characterization of film properties and multilayer deposition process control. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113938

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Two planar coil designs for a high pressure rf plasma source are investigated using spectroscopic techniques and circuit analysis. In an Ar plasma a truncated version of the commonly used ‘‘spiral’’ coil is found to produce improvements in peak electron density of 20% over the full version. A coil with figure‐8 geometry is found to move plasma inhomogeneities off of center and produce electron densities comparable to the spiral coils. Both of these characteristics are advantageous in industrial applications. Coil design characteristics for favorable power coupling are also determined, including the necessity of closed hydrodynamic plasma loops and the drawback of closely situated antiparallel coil currents. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113939

出版商:AIP    

年代:1995

数据来源: AIP