摘要:

The theoretical analysis of antiphase, surface‐emitting, complex‐coupled, distributed feedback (SE‐CC‐DFB) lasers is presented. The specific configuration chosen for analysis is relatively simple: a metallic second order grating placed atop a diode‐laser structure. This type of SE‐CC‐DFB structure can be fabricated by a lift‐off and evaporation process; can operate in a single‐lobed, orthonormal beam with a rather uniform near‐field intensity pattern, and external differential quantum efficiency, &eegr;d, values in excess of 30%. The dependence of the gain threshold on grating duty cycle for both the symmetric and antisymmetric (longitudinal) modes is presented and discussed. The external differential quantum efficiency for the symmetric mode is found to steadily increase with grating length at the expense of the degree of near‐field‐pattern uniformity. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116846

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

It has been shown earlier that GeSi/Si resonant‐cavity photodiodes can achieve high speed without sacrificing quantum efficiency. In this letter, we report a Si‐based resonant‐cavity photodiode that utilizes a Si/SiO2Bragg reflector. This structure is more compatible with standard Si processing technology than the GeSi/Si resonant‐cavity photodiodes. The absorbing region is a 1‐&mgr;m‐thick polysilicon layer that has been annealed to enhance secondary grain growth and the bottom mirror consists of three quarter‐wavelength pairs of Si and SiO2. After annealing the dark current was 9 &mgr;A at 1 V, the peak quantum efficiency was 44%, and the bandwidth was ≳1.4 GHz. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116847

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The luminescence properties of porousn‐type GaP are reported. Apart from the orange emission of bulk GaP, emissions in the blue and ultraviolet are observed. Evidence is presented to show that this blueshifted emission is not due to quantum confinement effects, as previously suggested, but to gallium oxide on the surface of the porous material. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116848

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Midinfrared InAs‐based and GaSb‐based semiconductor lasers with wavelengths from 3.3 to 4 &mgr;m have been used in a grating‐tuned external cavity configuration. At 80 K, a tuning range up to ∼8% of the center wavelength has been obtained. Power of 0.2 W peak, 20 mW average has been demonstrated for multimode operation with ∼1–2 nm linewidth. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116849

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A single frequency laser structure is obtained by coupling a high order mode of a semiconductor waveguide to a low index polymer waveguide. The device does not require a grating or regrowth, emits in a mode compatible with optical fibers, and may be immune to catastrophic mirror damage. The epilayers of the semiconductor waveguide use quarterwave reflectors to support a mode with a low enough effective index to phase match to the polymer waveguide. The coupling between the two waveguides is highly frequency selective and therefore stabilizes the wavelength. Preliminary structures emit in a single longitudinal and spatial mode, have 30 dB of sidemode suppression, and emit about 6 mW into a fiber compatible mode. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116850

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

AlInAs/GaInAs quantum cascade (QC) lasers operating at &lgr;=11.2 &mgr;m wavelength are reported. In pulsed operation the peak power is in excess of 50 mW at 110 K heat sink temperature and the devices have been operated at temperatures as high as 200 K. Continuous wave single‐mode operation with powers &bartil;7 mW at 10 K has been achieved. This work, combined with our previous reports on QC lasers, demonstrates that these new light sources can be tailored, by suitable quantum design, over a wide wavelength range (4–11 &mgr;m) using the same heterostructure material. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116851

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A novel nonlinear organic ionic material, or pyrylium salt dye, is synthesized and doped in the polymer matrix. These guest‐host‐type polymer films, which have no absorption in the blue‐wavelength region, have second harmonic generation (SHG) activities without the electric‐field poling process. The nonlinear optical coefficientd33is estimated as 1.10 pm/V at a 15 wt % of dye concentration. The nonlinearity is stable at room temperature and at 120 °C. The SHG device is fabricated using the nonpoled polymer film, and Cerenkov‐type phase‐matched SHG is observed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116852

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

cw‐laser‐induced local oxidation of ultrathin (3–60 nm) titanium films on glass in air is studied. It is shown, that the brightening of the films upon through‐oxidation forms a negative feedback to this highly nonlinear process. It offers the possibility of stable writing of oxide line structures narrower than the diffraction limited focused laser spot. The optimum metal film thickness is of the order of the light absorption length in the metal. Transparent isolated oxide lines and gratings with periods down to 250 nm and line width down to 165 nm were recorded in 6–15 nm thick Ti films on glass by using the radiation of the Ar ion laser (&lgr;=488, 514 nm). ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116853

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have investigated the early stages of film growth via deposition of size‐selected silver clusters on graphite, as a function of incident cluster size. For all sizes from 50 to 250 atoms per cluster, the deposited clusters are mobile and coalesce into three‐dimensional particles with a ‘‘universal’’ diameter of ≊14 nm, possibly a consequence of lattice strain between the silver and graphite. The 14 nm particles are found mainly in small aggregates, indicating that they themselves are to some degree mobile. We have also found evidence that the particle mobility is influenced by the cluster impact angle. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116854

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Molecular beam epitaxy of PbTe on BaF2(111) is studied using UHV–scanning tunneling microscopy and atomic force microscopy. It is shown that PbTe growth is totally dominated by growth spirals formed around threading dislocations (TD) that originate from the growth on the 4.2% lattice‐mismatched substrate. Due to dislocation annihilation, the TD density rapidly decreases with layer thickness, which results in a dramatic increase of the electron mobilities in the layers. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116855

出版商:AIP    

年代:1996

数据来源: AIP