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Single transverse mode selectively oxidized vertical cavity lasers

Description: Vertical cavity surface emitting laser (VCSEL) sources have been adopted into Gigabit Ethernet applications in a remarkably short time period. VCSELs are particularly suitable for multimode optical fiber local area networks (LANs), due to their reduced threshold current, circular output beam, and inexpensive and high volume manufacture. Moreover, selectively oxidized VCSELs are nearly ideal LAN sources since the oxide aperture within the laser cavity produces strong electrical and optical confinement which enables high electrical to optical conversion efficiency and minimal modal discrimination allowing emission into multiple transverse optical modes. In addition to the large demand for multimode lasers, VCSELs which emit into a single optical mode are also increasingly sought for emerging applications, which include data communication with single mode optical fiber, bar code scanning, laser printing, optical read/write heads, and modulation spectroscopy. To achieve single mode selectively oxidized VCSELs is a challenging task, since the inherent index confinement within these high performance lasers is very large.
Date: April 18, 2000
Creator: CHOQUETTE,KENT D.
Partner: UNT Libraries Government Documents Department

Near-Field Spectroscopy of Selectively Oxidized Vertical Cavity Surface Emitting Lasers

Description: Selectively oxidized vertical cavity surface emitting lasers (VCSELS) have been studied by spectrally resolved near field scanning optical microscopy (NSOM). We have obtained spatially and spectrally resolved images of both subthreshold emission and lasing emission from a selectively oxidized VCSEL operating at a wavelength of 850 nm. Below threshold, highly local high gain regions, emitting local intensity maxima within the active area, were observed; these were found to serve as lasing centers just above threshold. Above threshold, the near field spatial modal distributions of low order transverse modes were identified by spectrally analyzing the emission; these were found to be complex and significantly different from those measured in the far field.
Date: December 9, 1999
Creator: KIM,J.; BOYD,J.T.; JACKSON,HOWARD E. & CHOQUETTE,KENT D.
Partner: UNT Libraries Government Documents Department

GaAsSb/InGaAs type-II quantum wells for long-wavelength lasers on GaAs substrates

Description: The authors have investigated the properties of GaAsSb/InGaAs type-II bilayer quantum well structures grown by molecule beam epitaxy for use in long-wavelength lasers on GaAs substrates. Structures with layer, strains and thicknesses designed to be thermodynamically stable against dislocation formation exhibit room-temperature photoluminescence at wavelengths as long as 1.43 {mu}m. The photoluminescence emission wavelength is significantly affected by growth temperature and the sequence of layer growth (InGaAs/GaAsSb vs GaAsSb/InGaAs), suggesting that Sb and/or In segregation results in non-ideal interfaces under certain growth conditions. At low injection currents, double heterostructure lasers with GaAsSb/InGaAs bilayer quantum well active regions display electroluminescence at wavelengths comparable to those obtained in photoluminescence, but at higher currents the electroluminescence shifts to shorter wavelengths. Lasers have been obtained with threshold current densities as low as 120 A/cm{sup 2} at 1.17 {mu}m, and 2.1 kA/cm{sup 2} at 1.21 {mu}m.
Date: March 15, 2000
Creator: Klem, John F.; Spahn, Olga B.; Kurtz, Steven R.; Fritz, Ian J. & Choquette, Kent D.
Partner: UNT Libraries Government Documents Department

Single transverse mode selectively oxidized vertical cavity lasers

Description: Vertical cavity surface emitting lasers (VCSELs) which operate in multiple transverse optical modes have been rapidly adopted into present data communication applications which rely on multi-mode optical fiber. However, operation only in the fundamental mode is required for free space interconnects and numerous other emerging VCSEL applications. Two device design strategies for obtaining single mode lasing in VCSELs based on mode selective loss or mode selective gain are reviewed and compared. Mode discrimination is attained with the use of a thick tapered oxide aperture positioned at a longitudinal field null. Mode selective gain is achieved by defining a gain aperture within the VCSEL active region to preferentially support the fundamental mode. VCSELs which exhibit greater than 3 mW of single mode output power at 850 nm with mode suppression ratio greater than 30 dB are reported.
Date: April 26, 2000
Creator: CHOQUETTE,KENT D.; GEIB,KENT M.; BRIGGS,RONALD D.; ALLERMAN,ANDREW A. & HINDI,JANA JO
Partner: UNT Libraries Government Documents Department

Effective index model predicts modal frequencies of vertical-cavity lasers

Description: Previously, an effective index optical model was introduced for the analysis of lateral waveguiding effects in vertical-cavity surface-emitting lasers. The authors show that the resultant transverse equation is almost identical to the one typically obtained in the analysis of dielectric waveguide problems, such as a step-index optical fiber. The solution to the transverse equation yields the lateral dependence of the optical field and, as is recognized in this paper, the discrete frequencies of the microcavity modes. As an example, they apply this technique to the analysis of vertical-cavity lasers that contain thin-oxide apertures. The model intuitively explains the experimental data and makes quantitative predictions in good agreement with a highly accurate numerical model.
Date: April 18, 2000
Creator: SERKLAND,DARWIN K.; HADLEY,G. RONALD; CHOQUETTE,KENT D.; GEIB,KENT M. & ALLERMAN,ANDREW A.
Partner: UNT Libraries Government Documents Department

Composite Resonator Surface Emitting Lasers

Description: The authors have developed electrically-injected coupled-resonator vertical-cavity lasers and have studied their novel properties. These monolithically grown coupled-cavity structures have been fabricated with either one active and one passive cavity or with two active cavities. All devices use a selectively oxidized current aperture in the lower cavity, while a proton implant was used in the active-active structures to confine current in the top active cavity. They have demonstrated optical modulation from active-passive devices where the modulation arises from dynamic changes in the coupling between the active and passive cavities. The laser intensity can be modulated by either forward or reverse biasing the passive cavity. They have also observed Q-switched pulses from active-passive devices with pulses as short as 150 ps. A rate equation approach is used to model the Q-switched operation yielding good agreement between the experimental and theoretical pulseshape. They have designed and demonstrated the operation of active-active devices which la.se simultaneously at both longitudinal cavity resonances. Extremely large bistable regions have also been observed in the light-current curves for active-active coupled resonator devices. This bistability can be used for high contrast switching with contrast ratios as high as 100:1. Coupled-resonator vertical-cavity lasers have shown enhanced mode selectivity which has allowed devices to lase with fundamental-mode output powers as high as 5.2 mW.
Date: May 1, 2000
Creator: FISCHER,ARTHUR J.; CHOQUETTE,KENT D.; CHOW,WENG W.; ALLERMAN,ANDREW A. & GEIB,KENT M.
Partner: UNT Libraries Government Documents Department

Comparison of fabrication approaches for selectively oxidized VCSEL arrays

Description: The impressive performance improvements of laterally oxidized VCSELs come at the expense of increased fabrication complexity for 2-dimensional arrays. Since the epitaxial layers to be wet-thermally oxidized must be exposed, non-planarity can be an issue. This is particularly important in that electrical contact to both the anode and cathode of the diode must be brought out to a package. They have investigated four fabrication sequences suitable for the fabrication of 2-dimensional VCSEL arrays. These techniques include: mesa etched polymer planarized, mesa etched bridge contacted, mesa etched oxide isolated (where the electrical trace is isolated from the substrate during the oxidation) and oxide/implant isolation (oxidation through small via holes) all of which result in VCSELs with outstanding performance. The suitability of these processes for manufacturing are assessed relative to oxidation uniformity, device capacitance, and structural ruggedness for packaging.
Date: April 18, 2000
Creator: GEIB,KENT M.; CHOQUETTE,KENT D.; ALLERMAN,ANDREW A.; BRIGGS,RONALD D. & HINDI,JANA JO
Partner: UNT Libraries Government Documents Department

Q-switched operation of a coupled-resonator vertical-cavity laser diode

Description: The authors 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 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 ({approximately} 300 MHZ) forward-biased modulation regime to a faster ({approximately} 2 GHz) modulation regime under reverse-bias operation.
Date: February 8, 2000
Creator: FISCHER,ARTHUR J.; CHOW,WENG W.; CHOQUETTE,KENT D.; ALLERMAN,ANDREW A. & GEIB,KENT M.
Partner: UNT Libraries Government Documents Department

Bistable Output from a Coupled-Resonator Vertical-Cavity Laser Diode

Description: The authors 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 {micro}W to the electrical power applied to the top cavity. Theoretical analysis suggests that 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.
Date: July 20, 2000
Creator: FISCHER,ARTHUR J.; CHOQUETTE,KENT D.; CHOW,WENG W.; ALLERMAN,ANDREW A. & GEIB,KENT M.
Partner: UNT Libraries Government Documents Department

Two-Element Phased Array of Anti-Guided Vertical-Cavity Lasers

Description: We demonstrate for the first time anti-guided coupling of two adjacent vertical-cavity surface-emitting lasers (VCSEL's), obtaining a 1-by-2 phase-locked array at 869 nm. The lateral index modification required for anti-guiding is achieved by a patterned 3-rim etch performed between two epitaxial growths. In contrast with prior evanescently coupled VCSEL's, adjacent anti-guided VCSEL's 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 VCSEL's separated by 8 {micro}m. Moreover, phase locking of two VCSEL's separated by 20 {micro}m is observed, indicating the possibility of a new class of optical circuits based upon VCSEL's that interact horizontally and emit vertically.
Date: September 27, 1999
Creator: ALLERMAN, ANDREW A.; CHOQUETTE, KENT D.; GEIB, KENT M.; HADLEY, G. RONALD & SERKLAND, DARWIN K.
Partner: UNT Libraries Government Documents Department

Coupled Resonator Vertical Cavity Laser Diode

Description: We report the operation of an electrically injected monolithic coupled resonator vertical cavity laser which consists of an active cavity containing In{sub x}Ga{sub 1{minus}x}As quantum wells optically coupled to a passive GaAs cavity. This device demonstrates novel 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.
Date: September 16, 1999
Creator: CHOQUETTE, KENT D.; CHOW, WENG W.; FISCHER, ARTHUR J.; GEIB, KENT M. & HOU, HONG Q.
Partner: UNT Libraries Government Documents Department

Advanced Concepts for High-Power VCSELS and 2-Dimensional VCSEL Arrays

Description: We have developed high power vertical cavity surface emitting lasers (VCSELS) for multimode or single mode operation. We have characterized new cavity designs for individual lasers and 2-dimensional VCSEL arrays to maximize output power. Using broad area high power VCSELS under pulsed excitation, we have demonstrated the triggering of a photoconductive semiconductor switch (PCSS) with a VCSEL. We also have developed designs for high output power in a single mode. The first approach is to engineer the oxide aperture profile to influence the optical confinement and thus modal properties. A second approach focuses on "leaky-mode" concepts using lateral modification of the cavity resonance to provide the lateral refractive index difference. To this end, we have developed a regrowth process to fabricate single-mode VCSELS. The overall objective of this work was to develop high-power single-mode or multimode sources appropriate for many applications leveraging the many inherent advantages of VCSELS.
Date: April 1, 1999
Creator: Allerman, A.A.; Choquette, Kent D.; Chow, W.W.; Geib, K.M.; Hadley, R.; Hou, H.Q. et al.
Partner: UNT Libraries Government Documents Department

Room temperature continuous wave InGaAsN quantum well vertical cavity lasers emitting at 1.3 um

Description: Selectively oxidized vertical cavity lasers emitting at 1294 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave at and above room temperature. The lasers employ two n-type Al{sub 0.94}Ga{sub 0.06}As/GaAs distributed Bragg reflectors each with a selectively oxidized current aperture adjacent to the optical cavity, and the top output mirror contains a tunnel junction to inject holes into the active region. Continuous wave single mode lasing is observed up to 55 C. These lasers exhibit the longest wavelength reported to date for vertical cavity surface emitting lasers grown on GaAs substrates.
Date: June 5, 2000
Creator: CHOQUETTE,KENT D.; KLEM,JOHN F.; FISCHER,ARTHUR J.; SPAHN,OLGA B.; ALLERMAN,ANDREW A.; FRITZ,IAN J. et al.
Partner: UNT Libraries Government Documents Department

Selective Oxidation Technology and its Applications Toward Electronic and Optoelectronic Devices

Description: Selective oxidation of AlGaAs compounds has facilitated dramatic improvements in the performance of near IR VCSELS. Under the auspices of this proposal we have: (1) expanded our understanding of both the strengths and the limitations of this technology; (2) explored its applicability to other Al bearing materials; (3) utilized this technology base to demonstrate a variety of new electronic and optoelectronic devices; and (4) established the reliability and manufacturability of oxidized devices such as VCSELS. Specifically, we have investigated conditions required to maximize control of the oxidation process as well as those required to facilitate inhibit etching of the resultant oxide. Concurrently, studies were performed to extend the technology to other Al-bearing compounds such as Al(Ga)AsSb, InAl(Ga)P and Al(Ga)N. Several new devices utilizing the selective oxidation technology of AlGaAs, as well as Al(Ga)AsSb were be considered. On a separate front, we also explored the possibility of using oxidized AlGaAs and InAl(Ga)P to form GaAs/AIGaAs FETs. Finally, reliability and manufacturability issues of the high performance VCSELS fabricated using selective oxidation technology, were addressed.
Date: July 1, 1999
Creator: Spahn, Olga B.; Allerman, Andrew A.; Choquette, Kent D.; Vawter, Gregory A.; Klem, John F.; Sullivan, Charles T. et al.
Partner: UNT Libraries Government Documents Department