摘要:

An optically pumped GaN‐based vertical cavity surface emitting laser (VCSEL) is demonstrated. Laser emission near 363 nm is observed at room temperature from the surface of a VCSEL structure optically pumped along a cleaved sample edge by focused light from a nitrogen laser. The VCSEL structure, which was grown on a sapphire substrate by metalorganic vapor phase epitaxy, consists of a 10 &mgr;m GaN active region sandwiched between 30‐period Al0.40Ga0.60N–Al0.12Ga0.88N Bragg reflectors. At optical pump intensities above ∼2.0 MW/cm2, a narrow (<5 A˚) laser mode at 363.5 nm emerges from the GaN photoluminescence spectrum. This mode becomes the dominant feature of the spectrum at higher pump powers, and additional modes appear ∼1.3 nm above and below this mode at 362.1 nm and 364.8 nm. The ∼1.3 nm mode spacing corresponds closely with the 1.1 nm spacing predicted from an electromagnetics model of the VCSEL structure. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118104

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We use only nitrogen as the reaction gas to deposit on the cleaned Si wafer an extra‐thin Si nitride film (∼40 A˚) by electron cyclotron resonance method. Electroluminescence (EL) with its peak wavelength at about 7000 A˚ from the semitransparent Au/extra‐thin Si nitride film/p‐Si structure has been detected. The effects of forward bias and annealing on the EL have been studied. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118115

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Control of the polarization of vertical‐cavity surface‐emitting lasers (VCSELs) using a 240‐nm‐thick amorphous silicon subwavelength transmission grating (SWTG) is demonstrated. The grating, which has a strong polarization dependent reflectance and transmittance, was placed in front of the output window of a VCSEL. It was found that the SWTG can fix the VCSEL’s polarization in the direction perpendicular to the grating fingers, switch polarization directions, enhance the polarization ratio from 20:1 to over 200:1, and decrease the threshold current. Integration of these gratings into the VCSEL structure is discussed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118126

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report the laser operation of a thin‐film waveguide structure grown by the pulsed laser deposition technique. A 2.7‐&mgr;m‐thick crystalline film of neodymium doped Gd3Ga5O12(Nd:GGG) lases at a wavelength centered at 1.06 &mgr;m when pumped by a Ti:sapphire laser at 808 nm. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118091

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We show that the organic salt 4‐N,N‐dimethylamino‐4′‐N′‐methyl‐stilbazolium tosylate (DAST) is a very interesting material for electro‐optic applications in the near infrared. The electro‐optic coefficients, namelyr111,r221,r331,r113,r223, andr333, were determined in the spectral range of 700 up to 1535 nm using optical samples cut from large high quality bulk crystals. DAST combines large electro‐optic coefficients, e.g.,r111=77±8 pm/V at &lgr;=800 nm andr111=47±8 pm/V at &lgr;=1535 nm, with low dielectric constants, e.g., &egr;1=5.2±0.4. This combination leads to large polarization‐optical coefficients. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118101

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The frequency response and quantum efficiency (QE) of silicon‐on‐insulator (SOI) metal‐semiconductor‐metal photodetectors in the near‐infrared (∼800 nm) are greatly enhanced with a simple reactive ion etching to form electrodes inside the interdigitated trenches. Detectors with 1.25 &mgr;m trench spacing were fabricated on a SOI substrate with a 6‐&mgr;m‐thick silicon top layer. The unique device structure isolates carriers generated deep inside the semiconductor substrate and at the same time provides a highly uniform electric field throughout the active region of the detector, resulting in an instrumentation limited response time of 23 ps at 5 V bias and a −3 dB bandwidth of 2.3 GHz as measured at 790 nm. The dc responsivity is 0.12 A/W, corresponding to an external QE of 18.7% and an internal QE of 88.5%. The large bandwidth and good responsivity at the wavelength of interest, combined with their low operating voltages, make these detectors attractive for use in short‐distance optical communication systems. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118102

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have studied the lateral oxidation of AlxGa1−xAs (x=0.98 and 0.92) layers contained in vertical‐cavity lasers using cross‐sectional transmission electron microscopy. We find a fine‐grained (∼4 nm) cubic spinel phase of Al2O3in both the 2% Ga‐ and 8% Ga‐oxidized layers. The 8% Ga‐oxidized layers contract vertically by 6.7% and not the expected 20% for a fully dense Al2O3layer, with the 2% Ga‐oxidized layers showing a similar contraction. We observe a ∼17‐nm‐thick amorphous interface between the oxidized and unoxidized AlxGa1−xAs layers, which may account for the excellent electrical properties of these devices. We also observe metastable amorphous cavities associated with the moving reaction front. We infer the reaction proceeds from an initial amorphous phase that then transforms to a porous &ggr;‐Al 2O3layer.

ISSN:0003-6951    

DOI:10.1063/1.118103

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Theoretical and experimental results describing the application of wavelength modulation spectroscopy to density fluctuations are given. The effects of concurrent amplitude modulation, which often occurs when such experiments are performed with diode lasers are accounted for. It is shown that the characteristics of the signal magnitude at line center as a function of density include the expected increase with density,n, in the Doppler regime. In the effective collision broadened regime the signal magnitude at line center falls approximately asn−N, whereNis the order of the harmonic at which detection is performed. This result incorporates the well‐known result for direct absorption (N=0) in which the signal magnitude at line center stays constant while the linewidth increases in the collision broadened regime. It is shown that the sensitivity to density fluctuations measured by wavelength modulation spectroscopy around any ambient value depends strongly on the order of the detection harmonic employed, and that in many instances this sensitivity can be increased by using detection harmonics of order greater than the commonly used second order. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118105

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The effect of a postdeposition anneal on the structure and dielectric properties of epitaxial BaxSr1−xTiO3(BST) thin films (x=0.35–0.65) have been measured. The films were grown by pulsed laser deposition on LaAlO3(001) substrates. The films were single phase and (001) oriented with a lattice parameter larger than the bulk. The dielectric properties of thex=0.35 film exhibited a broad temperature dependence and a peak at 168 K, which is 36 K below the peak observed in bulk BST (x=0.35). Annealing films for 8 h in flowing oxygen at 900 °C caused the lattice parameter to decrease and dielectric properties to become more like the bulk. Annealing also resulted in an increased electric field dependent dielectric tuning without increased dielectric loss. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118106

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Electron paramagnetic resonance data demonstrate thatE&dgr;′, a radiation‐induced defect consistently found in buried oxide films, can also be generated in nonburied oxides after heat treatment in a sufficiently dry ambient. The center appears in samples heated in either N2or O2with moisture content on the order of 1 part per million. The near equality of the number ofE&dgr;′centers in the N2and O2treated samples implies that the presence of O2does not reduce the number of precursor defects. The results suggest that the center is related to a deficiency of hydrogen‐related species in the ambient rather than an O 2deficiency as has been previously suggested. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118107

出版商:AIP    

年代:1996

数据来源: AIP