摘要:

Quantum confined nanocrystals of PbS in glass were used as intracavity saturable absorbers to obtain passive continuous-wave mode locking in a Cr:forsterite laser. We obtained near transformed-limited 4.6 ps laser pulses at 110 MHz repetition rate, and a wide tunability range of 1207–1307 nm. The absorption saturation intensity of the quantum-dot PbS doped glasses was measured to be0.2 MW/cm2.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119843

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Extremely broadband AlGaAs/GaAs superluminescent diodes are fabricated on substrate with four quantum wells of different widths. By choosing 20, 33, 56, and 125 Å, respectively, for the four quantum wells, the spectrum could be broadened to several times that of the conventional superluminescent diodes. The measured spectra of the fabricated devices with such quantum-well structure show that the full-width at half-maximum spectral width could be as large as 915 Å. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119844

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A compact, narrow-linewidth, tunable source of THz radiation has been developed for spectroscopy and other high-resolution applications. Distributed-Bragg-reflector (DBR) diode lasers at 850 nm are used to pump a low-temperature-grown GaAs photomixer. Resonant optical feedback is employed to stabilize the center frequencies and narrow the linewidths of the DBR lasers. The heterodyne linewidth full-width at half-maximum of two optically locked DBR lasers is 50 kHz on the 20 ms time scale and 2 MHz over 10 s; free-running DBR lasers have linewidths of 40 and 90 MHz on such time scales. This instrument has been used to obtain rotational spectra of acetonitrile(CH3CN)at 313 GHz. Detection limits of1×10−4Hz1/2(noise/total power) have been achieved, with the noise floor dominated by the detector’s noise equivalent power. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119845

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A scanning thermal microscope was used to measure the temperature distribution inside a vertical-cavity surface-emitting laser. The peak temperature occurred at the intersection of the optical axis and the active quantum wells, and increased with input power at a rate of 0.74 °C/mW. Comparison with model predictions showed that thenmirrors and the substrate produce higher heat generation rates, possibly due to Joule heating and/or the absorption of spontaneous emissions that are often neglected in models. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119991

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Polycrystalline silicon (polysilicon) airbridges coupled to log-periodic and bow-tie planar antennas have been fabricated for mid-infrared radiation detection. The detectors in thermocouple and bolometer modes exhibit a higher electrical responsivity than previously reported metal based antenna-coupled thermal detectors. Measurements made at 10.2 &mgr;m wavelength indicate that the linearly polarized antennas have an on-axis cross-polarization ratio of about −4.5 dB and the pattern in the free-space side has a directivity of approximately 5–9 dB. The coupling efficiency is about 15&percent;. Frequency responses for modulated optical signals agree with thermal transport models. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119992

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report a monolithically grown optically addressed multiple-quantum-well spatial light modulator with high-frame rate operation(>44 kHz)and large sensitivity(<1 &mgr;J/cm2).The separated-detector-modulator device operates in the reflection mode and can provide a modulation gain of 35 with 60&percent; modulation depth. We also show that higher modulation gains(>50)can be achieved at the expense of modulation depth. In addition, by using a voltage pulse, we reduce the recovery time of the device from 90 ms to 1 &mgr;s such that high-frame rate operation can be achieved. We demonstrate 60&percent; modulation of the reflected readout beam at 44 kHz by only using43 mW/cm2cw writing illumination. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119993

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Pulse-propagation phenomena of accumulated photon echo signals was investigated for the4F3/2(1)–4I9/2transition of theNd3+ion doped with 20 ppm concentration in silicate glass fiber (core diameter of 6 &mgr;m) at 4.2 K using an 82 MHz mode-locked dye laser. The intensity of the transmitted probe pulses from theNd3+fiber was measured as a function of theNd3+fiber length. The fiber length for the maximum probe-pulse intensity induced by the pump pulses was determined to be 4 m when the pump pulses of 0.50 mW average power and the probe pulses of 0.25 mW average power were used. We derived the pulse area equations which take into account the coherent interaction between the pulses and theNd3+fiber. The fiber-length dependence of the signal intensity was explained well by the pulse area equations. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119994

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The three-dimensional photonic crystals used in this study were synthetic opals, composed of submicron silica spheres, close-packed in a face-centered cubic structure with a period of 200 nm, that exhibit photonic stopbands around 600 nm. We present measurements of the optical gain of CdS quantum dots (QDs) embedded inside the interstitials between the silica spheres. Unlike the usual gain spectra of CdS QDs in glass matrices, which display maximum gain at energies of the first quantum-confined transitions, for QDs embedded in photonic crystals the gain maximum is shifted toward the high-frequency edge of the photonic stopband (2.2 eV) far below the absorption edge of the semiconductor (2.5 eV). Studies of temperature, intensity, and orientation dependencies of the gain spectra allow one to ascribe the observed effect to gain enhancement caused by multiple coherent Bragg scattering of light in the periodic photonic crystal. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119995

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Two-photon pumped (TPP) frequency-upconverted lasing properties of a partially cross-linked fluorescent polymer are reported. This lasing medium is a cross-linked homogeneous copolymer with two major compounds: the chromophore, 4-[bis(2-hydroxyethyl)amino]-N-methylstilbazolium iodide, and the monomer, 2-hydroxyethyl methacrylate. The spectral, temporal, and spatial structures as well as the output/input characteristics of the TPP cavity lasing were measured using a 13 mm long polymer rod. The net conversion efficiency from the absorbed 1064 nm pump pulse energy to the∼606 nmupconverted cavity lasing energy was found to be∼4&percent;.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119996

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A multipole magnetic field was used to increase the ion density of an inductively coupled rf (13.5 MHZ) argon plasma for ionized magnetron sputtering of copper (Cu). Langmuir probe measurements showed an increase of plasma density over a factor of 2 with the application of the magnetic field. At an argon pressure of 15 mTorr and a rf power of 600 W, an ion density of1.2×1012 ions/cm3was achieved. When this plasma was applied to ionize the magnetron sputtered Cu vapor, a high emission intensity ratio from theCu+ion line to the Cu neutral line was observed from the optical emission spectroscopy, suggesting a high ionization fraction for the sputtered Cu vapor. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119997

出版商:AIP    

年代:1997

数据来源: AIP