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  • 1
    Electronic Resource
    Electronic Resource
    Interfacial characteristics of AlGaAs after in situ electron cyclotron resonance plasma etching and molecular beam epitaxial regrowth (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3105-3111 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Regrown/processed AlGaAs interfaces using secondary ion mass spectrometry, cross section transmission electron microscopy (TEM), and reflection high energy electron diffraction have been characterized. Two sets of samples, GaAs/Al0.4Ga0.6As (with GaAs on top) and Al0.4Ga0.6As/GaAs (with Al0.4Ga0.6As on top), are used as starting materials. For the GaAs/Al0.4Ga0.6As samples that are first exposed to atmosphere, the experiment is performed in an integrated processing system where etching and regrowth chambers are linked together by ultrahigh vacuum transfer modules. The etching process includes electron cyclotron resonance (ECR) hydrogen plasma cleaning of GaAs native oxides, ECR SiCl4 plasma anisotropic deep etching into Al0.4Ga0.6As, and an optional, brief Cl2 chemical etching. Regrowth is carried out using solid-source molecular beam epitaxy (MBE). Despite the in situ processing, significant amounts of C, Si, and O impurities at the 10, 5, and 50×1012 cm−2 levels exist at the interfaces. However, the impurity level is one order of magnitude smaller than that in air-exposed, ECR plasma etched and MBE regrown Al0.4Ga0.6As/GaAs of the set 2 samples. As revealed using TEM, isolated small particles (presumably correlated to aluminium oxides) exist at the regrown/processed interface of the set 1 samples, but no other defects such as dislocation are seen. Impurities and defects are mainly caused by the high reactivity of AlGaAs during ECR plasma etching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356162
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  • 2
    Electronic Resource
    Electronic Resource
    High single-mode power observed from a coupled-resonator vertical-cavity laser diode (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4079-4081 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a monolithic coupled-resonator vertical-cavity laser with an ion-implanted top cavity and a selectively oxidized bottom cavity which exhibits single fundamental-mode operation. The output powers are as high as 6.1 mW with side mode suppression ratios greater than 30 dB. The sizes of the implant and oxide current apertures are shown to be important for demonstrating the required selectivity for the fundamental lasing mode. With a fixed bias current on the implant cavity and increasing oxide cavity current, mode switching from single-mode operation to multimode operation and back to single-mode operation was observed. The intensities of the fundamental and first transverse modes were calculated by solving a set of multimode rate equations. The calculation indicates that the observed mode switching can be identified with changes in the optical length of the oxide cavity with increasing pump current. The observed mode dynamics are unique to coupled-resonator vertical-cavity lasers. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1426254
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  • 3
    Electronic Resource
    Electronic Resource
    Modal frequencies of vertical-cavity lasers determined by an effective-index model (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 22-24 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Previously, an effective-index optical model was introduced for the analysis of lateral waveguiding effects in vertical-cavity surface-emitting lasers. We show that the resultant transverse equation obtained in that model is almost identical to the one typically obtained in the analysis of dielectric waveguide problems, such as a step-index optical fiber. In this letter, we extend the effective-index model to obtain predictions of the discrete frequencies of the microcavity modes. As an example, we apply the analysis to vertical-cavity lasers that contain thin-oxide apertures. The model intuitively explains our experimental data and makes quantitative predictions in good agreement with a highly accurate numerical model. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126864
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  • 4
    Electronic Resource
    Electronic Resource
    Two-element phased array of antiguided vertical-cavity lasers (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3754-3756 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate antiguided coupling of two adjacent vertical-cavity surface-emitting lasers (VCSELs), obtaining a 1×2 phase-locked array at 869 nm. The lateral index modification required for antiguiding is achieved by a patterned 3 nm etch performed between two epitaxial growths. In contrast with prior coupled VCSELs, adjacent antiguided VCSELs can emit in phase and produce a single on-axis lobe in the far field. Greater than 2 mW of in-phase output power is demonstrated with two VCSELs separated by 8 μm. Moreover, phase locking of two VCSELs separated by 20 μm is observed, indicating the possibility of a promising class of optical circuits based upon VCSELs that interact horizontally and emit vertically. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125445
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  • 5
    Electronic Resource
    Electronic Resource
    Coupled resonator vertical-cavity laser diode (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3020-3022 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the operation of an electrically injected monolithic coupled resonator vertical-cavity laser which consists of an active cavity containing InxGa1−xAs quantum wells optically coupled to a passive GaAs cavity. This device demonstrates modulation characteristics arising from dynamic changes in the coupling between the active and passive cavities. A composite mode theory is used to model the output modulation of the coupled resonator vertical-cavity laser. It is shown that the laser intensity can be modulated by either forward or reverse biasing the passive cavity. Under forward biasing, the modulation is due to carrier induced changes in the refractive index, while for reverse bias operation the modulation is caused by field dependent cavity enhanced absorption. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125220
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  • 6
    Electronic Resource
    Electronic Resource
    Bistable output from a coupled-resonator vertical-cavity laser diode (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3319-3321 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a monolithic coupled-resonator vertical-cavity laser with an ion-implanted top cavity and a selectively oxidized bottom cavity which exhibits bistable behavior in the light output versus injection current. Large bistability regions over current ranges as wide as 18 mA have been observed with on/off contrast ratios of greater than 20 dB. The position and width of the bistability region can be varied by changing the bias to the top cavity. Switching between on and off states can be accomplished with changes as small as 250 μW to the electrical power applied to the top cavity. The bistable behavior is the response of the nonlinear susceptibility in the top cavity to the changes in the bottom intracavity laser intensity as the bottom cavity reaches the thermal rollover point. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1326840
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  • 7
    Electronic Resource
    Electronic Resource
    Q-switched operation of a coupled-resonator vertical-cavity laser diode (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1975-1977 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report Q-switched operation from an electrically injected monolithic coupled-resonator structure which consists of an active cavity with InGaAs quantum wells optically coupled to a passive cavity. The passive cavity contains a bulk GaAs region which is reverse biased to provide variable absorption at the lasing wavelength of 990 nm. Cavity coupling is utilized to effect large changes in output intensity with only very small changes in passive cavity absorption. The device is shown to produce pulses as short as 150 ps at repetition rates as high as 4 GHz. A rate equation approach is used to model the Q-switched operation yielding good agreement between the experimental and theoretical pulse shape. Small-signal frequency response measurements also show a transition from a slower (∼300 MHz) forward-biased modulation regime to a faster (∼2 GHz) modulation regime under reverse-bias operation. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126227
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  • 8
    Electronic Resource
    Electronic Resource
    Improved optical switching extinction in three-electrode Ti:LiNbO3 directional couplers (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 2097-2099 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Utilizing three electrodes and three independent voltages in Ti:LiNbO3 directional coupler optical switches, we have achieved significant improvements in switching extinction over the standard uniform Δβ configuration. The reductions in optical crosstalk vary from 3 to 24 dB for both switching states of several fabricated devices. We have observed a bar state extinction of −47.8 dB, which is the largest extinction ratio reported to date. We find that switching measurements are limited by the largest contrast ratio which can be obtained in the optical waveguides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98959
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  • 9
    Electronic Resource
    Electronic Resource
    Removal of GaAs surface contaminants using H2 electron cyclotron resonance plasma treatment followed by Cl2 chemical etching (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2658-2660 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a novel dry process to remove the surface contaminants C, Si, and O from GaAs substrates. This method utilizes an electron cyclotron resonance hydrogen plasma to remove the native oxides, followed by a very brief Cl2 chemical etching of GaAs to further reduce C and Si residues, and a final vacuum anneal. Characterization by secondary ion-mass spectrometry (SIMS) typically reveals the removal of C, Si, and O at the overgrown/processed interface to the levels below the SIMS detection limit. The as-processed GaAs surface, a Ga-stabilized reconstructed (4×6), is atomically smooth, and is as clean as a surface of freshly grown GaAs epilayers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109277
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  • 10
    Electronic Resource
    Electronic Resource
    Microstructure of laterally oxidized AlxGa1−xAs layers in vertical-cavity lasers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 19-21 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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 Al2O3 in 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 Al2O3 layer, 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 γ-Al 2O3 layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118103
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